Firewheel custom battery pack

[esaj]

I finally reached a (somewhat compromised) decision regarding the custom battery packs of the Firewheel. I ended up ordering 4 packs, each with their own BMS. The BMSs should have 2.9V overdischarge protection cutoff voltage and XXX overcurrent protection (to become more precise later as the final BMS is chosen, should be between 30A and 120A).

The cells will be Panasonic NCR18650PF 2900mAh, originally I was looking into LG INR18650 MJ1's (3500mAh), but it would have pushed the price up a bit too much. The NCR is actually NCA (LiNiCoAl)-chemistry, so it's the same as the LG, and should be (probably) about the best choice for wheels:

  NCA - Li-aluminum

This chemistry is similar to INR, but without the benefit of manganese. These batteries tend to support lower discharge currents, but make up for it with great capacities and cycle life. They also tend to be more resistant to physical shock, making them good options for e-bikes. Tesla uses them for its awesome electric cars.

While the capacity is not as high as with MJ1's, the price difference was great enough, that I could get 4 16S1P-packs of these for a little more than what 3 packs of MJ1's would have cost. I figured it's worth it, as the total capacity for four packs with 2.9Ah is greater than the three packs with 3.5Ah. On the plus side, also the load will be divided among four packs instead of three.

A single pack will be 16S1P, with it's own BMS and will contain 174Wh at nominal 60V voltage (60V * 2.9Ah = 174Wh). The REAL nominal voltage of typical 18650 Li-Ion cells is around 3.6-3.7V per cell, so that would be 57.6-59.2V, but usually the 60V rounded value is used. Total of four packs will contain 4 * 174Wh = 696Wh. That's actually the SAME capacity as the original "779Wh" -pack for Firewheel. Michael VU posted a picture of the label on F779 -battery pack, and it actually says 60V 11.6Ah... that raised some eyebrows, as 60V * 11.6Ah = 696Wh. What I concluded was that they must have actually used the MAXIMUM voltage of 67.2V (4.2V per cell) to calculate the capacity...

67.2V * 11.6Ah = 779.52Wh

And then rounded it down, maybe they thought F779 sounds better than F780?

So, I get four independent packs with their own BMSs instead of four 4S4P-packs wired into one BMS (like the original F779 battery seems to be). What's the use?

The single packs can be separated, if need be, I could take packs from the Firewheel and put them into another wheel, should I like it, and still ride them both. A single 174Wh pack should fit pretty much any wheel, as they've made to measurements to fit into the very cramped battery compartments of the Firewheel.

Failure of a single pack (for example wiring) or the BMS protection triggering will still leave 3 other packs that keep on working. With single BMS in 4S4P packs wired together, the wheel would cut off at this point. Also, the BMSs have very low voltage for overdischarge/high current for overcurrent cut off, so the likelihood if it happening is lower. Btw, I don't currently plan to be shunting these, unless it's absolutely necessary, I expect the four packs to be able to keep the voltage high and current low per pack, so the safety shouldn't trigger unless there's something really wrong in the pack.

Four packs dividing the load means that there's going to be much less voltage sag (same is true for the original F779-pack) under high load. The Panasonic cells can give 10A continuous discharge (so 40A for all the packs) and 18A pulse discharge for 5-6 seconds (that'd be 72A, probably the mainboard or motor would be long gone before the batteries would stop, if such current was ever even needed). Will I need such currents ever? Probably not, considering if the 550W rated / 1350W peak for the Firewheel motor is even correct, and the voltage would drop to around 56V (3.5V per cell) where the main board stops you from riding, even pulling peak power at that voltage would still be "only":

1350W / 56V = around 24.1A

Divided to four packs, that's around 6A per pack, not even close to the maximum CONTINUOUS drain. At the same low voltage and riding at rated max power for longer term (it would have to be a little over the main board stopping voltage, so I could continue, but anyway):

550W / 56V = around 9.82A

Again, divided to four packs, that's around 2.46A. So, you could say the discharge capability is somewhat over the top for my use   But I don't like to leave things to chance, besides since I usually ride the 264Wh to empty in about an hour, that gives me an average power use of 

264Wh / 1h = 264W

I'm not even going to calculate the current, I'll leave it as homework to anyone who's interested...   The point is, even with low voltages and high power draw, I doubt I could overpower the batteries.

But of course the most important aspect is the range. With the current batteries, I've got fairly good ranges (up to almost 26km on warm weather, or "only" 18.25km on heavy head winds and colder temperature) compared to the battery capacity. Still, I need to turn around after about 9-13km, unless I want to risk having to carry the wheel back home (Imagine doing that on hot weather with the safety gear I always wear? Something I don't want to try...). No more range anxiety! I've also got some pretty long (going over 50km at best) routes planned, which should be possible with this high capacity.

It's not probably going to be the same ratio of Wh/km with this many packs (actually, I'd maybe expect it to be less Wh needed per km due to less stress per pack?), but if using a value of 15Wh per km (18.25km on 264Wh battery is actually 14.46Wh per km), the 696Wh should take me around 46.4km. If using the value of 10,23Wh per km (as in 25.8km on 264Wh), the range should be around 68km.  But of course we'll see what the reality is, most of the time I probably won't be needing the full range the packs give me, but won't have to worry about them running out on accident either

Of course having custom battery packs made to measurements and wishes isn't exactly cheap, but I thought we only live once... And it actually seems to cost me about the same as if I had ordered the original F779-pack from the factory with customs & taxes (probably different on other countries, depending on your customs & tax rates). Another upside is that I've got a domestic company building me the pack, it's carefully assembled, comes tested and with warranty (not to say that the original packs wouldn't have warranty, but it's a bit easier for me to ship a possibly faulty pack inside the country than sending it to the other side of the world). Plus since it's specifically made for me, I'd expect the testing and quality to be a "bit" better than on the original packs... have you seen the pictures when vee73 was making the shunt-mod to the original pack? One of the power wires wasn't even soldered properly, it was held in only by the shrink wrap!

But I think we've all heard of the (sometimes) dubious quality of Firewheels. Hopefully they'll QC will wake up some more in the future, the wheel is actually really good once they solve the "minor" problems of BMS and sealing and do better quality control...

Now, I've only just set the ball rolling on the project, and there could be still be problems ahead. I'm a bit worried if the packs will actually fit, despite (more or less) careful measurements, as the compartments have concave surfaces, which make it hard to estimate what can fit and what can't. Plus I could bungle up the wiring all by myself and end up with a dead pack, motherboard or something... 

It will probably take some time before I actually have the packs and get them installed on the wheel itself. Right now the wheel is in pieces in the next room, waiting if I still need to check something or take more measurements, and then reseal it with silicone so I actually dare to ride it again... But we'll see.

Happy wheeling everyone!

PS. Firewheel is sad... "Put me back together and ride me, goddamnit!":

[esaj]

Now I'm having problems with the new brand-specific forums already... This isn't really that Firewheel-specific, so I probably should have posted it in the Mods & Repairs from the start...    Moving.

[esaj]

Minor change in plans, the cells are going to be LG INR18650MH1's, 3200mAh, 10A continuous, 20A pulse current. Still using LiNiCoAl (NCA)-chemistry. The change was due to the Panasonics being out of stock, so instead of waiting, I opted to pay a little more for MH1's (went up by less than 10%, the MH1's are the lower capacity version of the MJ1's I was eyeballing at, but using MJ1's would still push the price up >10% from what I'll be paying for the MH1's). So total battery capacity has gone up to nominal 60V * 3.2Ah * 4 = 768Wh, max 67.2V * 3.2Ah * 4 = around 860Wh.

I finished moving the secondary PCB to mainboard compartment today, the pictures are here: http://forum.electricunicycle.org/topic/613-firewheel-pcbs-connectors-battery-wiring-older-gen/?do=findComment&comment=5640

Currently the wheel is waiting for silicone to dry, the motor is already attached to the other shell-half, tomorrow I'll power it back up and finish the sealing when combining the shell halves. Then it should be good to go once the final sealing has dried a bit. Will have to repeat the tear down once I get the new batteries, and replace the seals then. Also will need a minor mod (extra wire-channel), as I cannot wire the batteries through the mainboard-compartment anymore...

[esaj]

I still don't have the custom-packs, but have done other preparations for them. I went shopping and got:

-Some shrink tubes, different sizes
-Small wire ties
-Soldering flux
-Desoldering braid
-10 meters of 1.5mm² -wire, both red and black
-Some smaller screw terminals than what I had before
-One XT60-connector pair (both male and female)

I also bought some tools and other stuff I might need outside this project too

-Files
-Basic multimeter
-Some basic electric/electronics -tools and accessories (Abico-pliers, better wire stripping pliers than I had, abico-connectors)
-A small bench vise
-A vernier caliper

I still need to get some things, like rubber mat (I know where I can get some 2mm thick mat in big pieces for cheap, unfortunately the next bigger thickness would be 6mm, which is a bit too much) for cutting extra sealants that go between the lids/metal plate and the edges for the battery- and mainboard-compartments, silver thermal paste, more acetone and maybe some extra connectors.

I have also ordered a couple of 100V DC voltage led/7-segment -displays (the kind that self-power from the wires they're measuring) and one 100V DC voltage/current led/7-segment -display with 50A shunt ( http://www.aliexpress.com/item/DC-Car-LED-Red-Blue-Dual-display-DC-0-100V-50A-Voltmeter-Ammeter-2in1-Voltage-Current/1684125289.html ) via Aliexpress, but they'll probably take at least a couple of weeks to arrive. I don't yet know where to power the voltage/current-display from, as it needs separate powering (DC 4.5 - 30V).

Here's my (yeah, I can't draw... ) preliminary diagram of the batteries <-> XT60 <-> Mainboard -connections with the voltage/current-display:

I was at first thinking of using 8-piece screw terminal, so I could screw/unscrew single batteries on and off the connection (I'd rather not solder them all directly to the XT60), but that's going to be a problem space-wise (remember that I need another 8 connections to the charging side!). Maybe 2 pieces of molex-connectors, molex has 4 pins, so 1 molex with the 4 positive wires from batteries and another with 4 negatives... and then another two for charging side. Suggestions on connectors? And does anyone know where I can draw between 4.5V and 30V from the motherboard "safely" for the display?

Today I took also some time to make some plastic parts with the help of the old shells vee73 sent me along with the wheel  (the link to imgur-album is http://imgur.com/a/O0sGi , to remind myself in case I ever need it ), they've actually been pretty useful when planning:

This is the channel between the two battery compartments on the side that does NOT hold the main board. That's pretty normal 15mm diameter plastic electric insulation pipe, used usually in houses for wiring. I've got LOTS of the stuff in the attic, so decided to go with what I have. The original channel above the pipe will be totally sealed off with silicone, and I will drill holes on the sides, so the wires can be run through the pipe.

This is just a mock up of what I will do on the same side with the channel going to front of the wheel from the front battery compartment. The final pipe will of course be longer (this was a leftover from when I was doing one the angled pipes and ended up cutting it too short ).

I had to file off a bit from the sides of the pipe for it to fit into the existing channel.

This was the hardest pipe to make, due to the angles, took a couple of tries and lots of filing (less than a millimeter at a time) until I got it pretty much correct (it could still be better, there's <1mm hole on one side between the pipe and the compartment side, but the pipe ends will be sealed with silicone anyway), the angles were a b**tch. This is the mainboard side front battery compartment, the old wire channel going up to mainboard compartment will be totally sealed off and the battery wiring will go straight to front. There's also a clear plastic shield (hard to see in the picture) on the upper wire channel going to front of the bike from the mainboard compartment. I was just testing around with plastic cut off from a candy box lid. It's pretty easy to work with, as it can be cut with scissors, yet sturdy enough.

Another angled pipe, going from top of the mainboard compartment next to the handle. This will be used to draw some of the wires coming from mainboard (probably at least backlight, maybe mode switch, speaker, power button...), as the only original wire channel going to the front would be so damn crowded with all the wires (large multi-wire flat cable for battery display, front & backlight, speaker, mode switch, power switch, light switch, battery power & charging wires...) that I don't I could fit them otherwise.

I tried to cut another clear plastic piece for the channel between the motherboard-side battery compartments. Can't put a pipe here, as the motor cable will run to the mainboard through the upwards going wire channel. Currently I have a metal piece I made when doing the teardown and reassembly, but I think this could work better to also protect the battery wire channels... Might have to still put some more thought into this.

The plastic piece sits a bit on top of the wire channel "walls", need to file them down... otherwise it's pretty perfect thickness, as it drops just below the battery compartment wall edge, when against the screw holes.

Also tried to remove one of the unnecessary screw-bumps in the battery compartments, was easy to cut off with a Dremel-clone, need some filing & silicone sealing, but this is what I'll do with the real shells.

Another thing I'm going to do is to take the metal plate from the old burned mainboard (yeah, have that too), and use the burned board to find the places for new screwholes for fitting both PCBs on the plate. When the time comes, I'll remove the working mainboard from the much more worn metal plate currently in the wheel (the studs of vee's winter tire have actually scratched it pretty badly, and some of the screw -"ears" have bent & broken), place it and the secondary PCB on the plate and use thermal paste between the heatsink and the plate for better thermal conductivity.

 

[dmethvin]

I still need to get some things, like rubber mat (I know where I can get some 2mm thick mat in big pieces for cheap, unfortunately the next bigger thickness would be 6mm, which is a bit too much) for cutting extra sealants that go between the lids/metal plate and the edges for the battery

 

 When I did the sealing originally, I had some neoprene and silicone sheets of different thicknesses that I tried using for gaskets. The problem I ran into was that the black plastic plates are too flexible, especially on the side near the hub where there is a pretty long section with no screws at all. It was worse with my first try, because I didn't cut the gaskets to go under the screw hole tabs and tightening down the screws made the plate warp. So even if you create gaskets you will still need silcone sealant to be sure it closes well, I just decided to use nothing but silicone sealant in the end. The gaskets might make a good "shim" to expand the battery compartment a bit though. 

(from the diagram: "Is there +12V on the motherboard?)

What does the head/tail light run on? The component that blew out in my first controller board was a DC/DC converter for the lights, so it must have been stepping down the voltage. See http://forum.electricunicycle.org/topic/244-firewheel-f260-good-news-and-really-bad-news/#comment-2359 .

Also tried to remove one of the unnecessary screw-bumps in the battery compartments, was easy to cut off with a Dremel-clone, need some filing & silicone sealing, but this is what I'll do with the real shells.

 All those pictures looked painfully familiar. 

[esaj]

 When I did the sealing originally, I had some neoprene and silicone sheets of different thicknesses that I tried using for gaskets. The problem I ran into was that the black plastic plates are too flexible, especially on the side near the hub where there is a pretty long section with no screws at all. It was worse with my first try, because I didn't cut the gaskets to go under the screw hole tabs and tightening down the screws made the plate warp. So even if you create gaskets you will still need silcone sealant to be sure it closes well, I just decided to use nothing but silicone sealant in the end. The gaskets might make a good "shim" to expand the battery compartment a bit though. 

Yeah, I'm pretty sure I'll need to raise the lids a bit, as each of the batteries will also have their own BMS, adding to thickness... And I was planning on cutting the mats so that the screws go through the mat also. And yes, silicone over everything at the end, the mat is more for raising the space than actually sealing (although it should make it more water resistant too).

 

What does the head/tail light run on? The component that blew out in my first controller board was a DC/DC converter for the lights, so it must have been stepping down the voltage. See http://forum.electricunicycle.org/topic/244-firewheel-f260-good-news-and-really-bad-news/#comment-2359 .

That's what I meant by getting the voltage "safely"... I don't want to blow the mainboard  or cause a cutout because the display is causing something wacky to happen with the other parts. I do have couple of self-powered (voltage only) displays coming too, if I'm too unsure of setting up the voltage/current -display, I'll go just with voltage display, since it can power itself straight from the battery wires (but then I'll need an on/off -switch for it, so it doesn't suck the batteries empty).

 All those pictures looked painfully familiar. 

Yeah, I really wish the designers had put more effort on the insides (outside-only accessible compartments!)... but at least it's not too hard to work on. We'll see what happens with the "real" shells.   I think I'll remove the bigger bumps too to get as much space as possible, then I probably have to get the same bumps off the black round plastic parts outside, and fill the hole with silicone or something. 

I do hope there isn't much tolerance-differences between different shells, it would suck to find out that the pipes won't fit on the real shell due to few millimeter throws here and there, I spent a good while filing & trying them on to get the correct angles... 

About the battery wiring, maybe I should go just with putting all the positive- into one hole (and negatives in the other), then I'd get away with two-piece screw terminals or simple connectors, and still be able to get them of one at a time, if need be.

[hobby16]

Here's my (yeah, I can't draw...

) preliminary diagram of the batteries <-> XT60 <-> Mainboard -connections with the voltage/current-display:

I was at first thinking of using 8-piece screw terminal, so I could screw/unscrew single batteries on and off the connection (I'd rather not solder them all directly to the XT60), but that's going to be a problem space-wise (remember that I need another 8 connections to the charging side!). Maybe 2 pieces of molex-connectors, molex has 4 pins, so 1 molex with the 4 positive wires from batteries and another with 4 negatives... and then another two for charging side. Suggestions on connectors? And does anyone know where I can draw between 4.5V and 30V from the motherboard "safely" for the display?

You can get the digital display's power from 5V of the motor's hall sensors connector (5 wires, red=5V, black=0V, other colors= 3 signal lines). I don't have the mainboard picture but when you have it, show me and I can tell you where to pick the 5V.

As to the connectors, screw terminals are fine. You don't need to use 8 terminals, 4 would or even 2 would be enough, if they are of big diameter. Otherwise,  T connectors commonly used in RC are small too, with Aliexpress, it should now cause no problem to order them.

[esaj]

You can get the digital display's power from 5V of the motor's hall sensors connector (5 wires, red=5V, black=0V, other colors= 3 signal lines). I don't have the mainboard picture but when you have it, show me and I can tell you where to pick the 5V.

Yeah, I found out that the main PCB has the pins described in the backside, when taking of the old burned board from the metal plate, see here (I did already message to you about this, but just in case other people reading this are interested): http://forum.electricunicycle.org/topic/613-firewheel-pcbs-connectors-battery-wiring-older-gen/#comment-6719   

There's actually +12V and +5V output-pins, but all I'm worried about is if it's "safe" to pull extra current (<20mA) from those, knowing that the DC/DC -voltage lowering chip was the part which burned easily in these older PCBs.

As to the connectors, screw terminals are fine. You don't need to use 8 terminals, 4 would or even 2 would be enough, if they are of big diameter. Otherwise,  T connectors commonly used in RC are small too, with Aliexpress, it should now cause no problem to order them.

After chatting with vee73 about the screw terminals, I don't think I'm going to use them at all. The vibration of the wheel can cause the wires to slowly come off and the connectors are prone to oxidization over time. Also, the space is going to be pretty limited, as the 50A shunt for the display is 25 x 120 x <something, not displayed in the pictures> millimeters, and there's lots of other connectors filling the cramped space. Without the shunt the display could only take 10A max.

Instead of screw terminals, I've been looking at using JST RCY -connectors for the charge side (4 female connectors directly off from the charge port, each with their own wires, male connectors on battery-side charge wires), and at first thought I'd use 4 male Deans Ultra (what I think is what you mean by T-connectors) -connectors to the female XT60 (which is then connected to mainboard male XT60), and put the males on the battery-side discharge wires, but after checking their dimensions, they're too wide to pass through the electric piping I'm going to use for wire channels, so I need to find something smaller that has high amp-rating (20A or more, as that's what the max pulse per battery should be around, although I probably won't ever need that much per pack, as I suspect the 80A total current would blow everything in it's way )... The JST RCY's are small enough to pass through the piping, but I don't want to use similar connectors on both charge- and discharge-side, to prevent accidentally wiring them wrong, and also the JST's cannot take much current (less than 5A, I think, some source said that you shouldn't put more than 2A through these).

Maybe 50A Anderson Power Poles would be a good fit for the discharge side (as I can use single connector per wire, and put them through the piping one by one), if I can find a shop which sells them. The JST's and Deans Ultras are available from a couple of local RC-stores, but at least their pages didn't list the Andersons. Another option might be some bullet-connectors, but I'm worried if they'll stay connected or slowly disconnect with the vibration...

It's still going to be crowded inside the front of the wheel with all the connectors (especially if there are 8 Anderson Power Poles), but I'd preferably not solder the discharge wires directly to the XT60 female -connector, or the charge wires to the port/single connector, just as a precaution, if I later on have to remove one or more battery packs (either due to breakage & warranty repair, or if I want to take one or two packs to another wheel), so I could get them off easily without having to do resolderings or such. That being said, it's more probable that if the batteries work fine, I won't be taking them out for a long, long time

[esaj]

I contacted the company building the battery packs for me, the current status is that they're waiting for the BMS's to arrive (guess they had to order the 16S-BMS from abroad) until the assembly starts (of course it would be possible to put the cells together already, as those are available, but not so much use without a BMS for testing). I just started my summer vacation, so I have the time to go look out for the missing connectors (JST & Anderson) over the next week and to get some heavier gauge wire for the discharge-side of the battery packs (currently only have 1.5mm^² kind. which can't take currents over 14A so well...). I know a place where to get the rubber mats + heavier gauge wire for fairly cheap, but also need to go buy the JST-connectors and likely will have to order the Anderson-connectors from further away. I probably can get the thermal paste from local shops, so I should be covered for now. Also, the displays are coming from Asia (China/Singapore), so don't know how fast they'll arrive (the shipments have already been dispatched, so 2-4 weeks...), if they don't make it in time, I'll just install the displays later on.

[esaj]

Still haven't got the battery packs, hopefully soonish... in the mean time, I've gotten the necessary equipment & materials for building the other parts. Last night I started to make the connectors for the batteries, here's the link to imgur-gallery: http://imgur.com/a/TJUt1 

It looks like using off-site images in posts doesn't work for me after the last forum software update, so I decided just to comment on the pictures.

Edit: a few notes about wires, soldering & the connectors:

AWG to mm^2 -conversion chart: http://www.rapidtables.com/calc/wire/awg-to-mm.htm

Cable-sizing calculator: http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

Soldering tips: http://www.tjinguytech.com/soldering

 

The JSTs need to be crimped carefully (especially since I was using thicker wire than what they're made for), the housings are really tight, and if the crimping isn't tight enough, you can't get them to fit all the way into the housing and lock in place. My first attempt wasn't well enough crimped, and the connector wouldn't go all the way in, but got stuck so tight that I couldn't get it out either  

Video of soldering JST: https://www.youtube.com/watch?v=54hq2s3kTJk

The Deans is a bit hard to solder the way I did it, most video tutorials show the wire being placed on one side of the tab and then soldered, but I wanted more secure (and bigger area) connection, so I cut the grooves instead. The metal saw blade was little thinner than the tab, so after cutting the groove, I had to heat up the wire to get the solder running so the conductors would move a bit and I could insert the tab all the way. Then heated up both the tab and wires & added more solder to get good connection.

Video of soldering a Deans: https://www.youtube.com/watch?v=opMBIIB6l1M

The Andersons are pretty easy to solder (these are the "middle"-sized connectors, there are separate sizes for 15A, 30A and 45A, that all go to the same housing, these were 30A). I first pre-tinned the wires and the connector, then soldered the wire to the connector (so it stays in place). Then I crimped the connectors from the top with the Abiko-pliers (red & blue crimp-slots in the pliers, I didn't have "real" Anderson-pliers), so I could see the wire from between the two sides of the crimps. Then soldered the wire tightly (heat it and the connector through the groove between the crimp sides & solder), and then crimped them sideways. The Anderson housings are large enough that the crimp doesn't have to be so precisely sized. Also note that in the 3rd last picture, showing the soldered connectors, there's some solder on top of the connector after the crimping parts, THIS HAS TO BE TAKEN OFF before inserting the connectors into the housings, otherwise you can't either get them in, or the lip will stay pushed a bit downwards, and the connection between the two Andersons (there will be similar connectors at the battery discharge wires) won't be good.

Some good tips about Andersons: http://www.westmountainradio.com/kb_view_topic.php?id=ST166

 

[esaj]

Finally, the BMS's are in a mail sorting center and should arrive tomorrow (they took their time to arrive, plus the customs held them back for something like about a week? ), and the pack assembly can finally begin. I was informed that they're being made over the weekend, and I should get them next week (so probably tuesday or wednesday?).

 

I visited my step brother today (on my wheel, of course) to get the bolt threads made for the new mainboard holes on the metal plate (btw, it looks like they're M4 X 0.5 threads, not X 0.7, if anyone needs to do the same sometime). This way I can either place the secondary PCB on the plate too, or attach the shunt to it (or both, but then it becomes very crowded). The battery charge- & discharge-side connector-sets are ready (of course I also need to solder the connectors to the batteries themselves, after they arrive), all I need to do anymore is cut the rubber sealants for the battery compartments & mainboard compartment (they'll also elevate the battery compartment lids for a couple of millimeters, to get a little more space depth-wise).  Unless I've forgotten something... 

[EUC Extreme]

Okay. Good luck with your project. I hope everything goes well.

[esaj]

Finnish postal service showed it's "high quality service" again, and LOST the BMS-package for a while, so it didn't arrive until today (was supposed to be there by friday, so the packs could have been built over the weekend), so it's likely going to still take a few days...    Only with my luck. Funny story, there's actually a package in the postal tracking system that I've heard has circled the nation since 2009 and still keeps going:  http://bit.ly/1hk4mPQ  Don't know if it's a "ghost" or a glitch in the system, or if there's really a physical parcel that's being sent around the nation year after year (and sometimes marked as leaving the nation).

 

Here's the first piece coming along, tabs attached and the BMS wired in place, the BMS is larger on one side than the originals on Firewheel, but it isn't as thick (or deep, which ever way you think about it), the BMS is about 5mm thick at highest, so it SHOULD fit, at least with rubber sealings around the battery compartment edges lifting the lids up a bit... if need be, I'll go as far as to seal the compartments entirely from the inside and cut openings for the BMS's to the outside behind the black round plastic part that's screwed to the shell to get a few millimeters more depth. 

[esaj]

This project has had so many set-backs (mostly due to BMS delays), that it's actually kind of funny (but I'm a bit pissed, too )... After about 7 weeks, it looks like I'll finally (fingers crossed) have the three battery packs tomorrow. Yes, three. The fourth BMS was faulty, a replacement is on the way, but if it takes as long as the first three, it'll be near to middle of October... Anyway, I took the wheel to pieces last evening, and have been scrubbing off the old silicones and soldered the new charging connectors to the charge port:

Left the old connector there too, just in case... 

As if all the delays weren't enough, it also looks like my mainboard might be developing a fault:  http://forum.electricunicycle.org/topic/957-firewheel-startup-failure/

What else could still go wrong? Well, the postal service tracking system shows that while the package has been sorted, it doesn't look like it's moving anywhere yet, so it might not arrive tomorrow, of course they could also lose it, or destroy it, or mail it into wrong address...   The mainboard might give out after I get everything back together, or the packs could just catch fire or blow up the moment I power the wheel. Or a combination from all of these.

Due to the possible mainboard problem, I've decided to skip moving the mainboard to another metal plate, as I originally planned (the idea was to stick both PCBs & the current-measuring shunt to the plate, and add thermal paste between the mainboard heatsink and the plate). Will have to find another place for the current/voltage -display shunt for now. Also I've made a small battery case for 9V battery with an on/off-switch for the current/voltage-display, as it seems it isn't that accurate unless using an external power source. It can power itself from the wires where the voltage is being measured, but when I was calibrating it with a friends configurable power supply, the values were sometimes off, but seemed to be consistent when powering from a separate battery. The case will be attached with velcro on the side of the wheel, and the power-connector will be run through the side of the wheel. I'll post more pictures and details after I get around to putting it all together.

[Tilmann]

...keeping my fingers crossed ...

[robca]

I have also ordered a couple of 100V DC voltage led/7-segment -displays (the kind that self-power from the wires they're measuring) and one 100V DC voltage/current led/7-segment -display with 50A shunt ( http://www.aliexpress.com/item/DC-Car-LED-Red-Blue-Dual-display-DC-0-100V-50A-Voltmeter-Ammeter-2in1-Voltage-Current/1684125289.html ) via Aliexpress, but they'll probably take at least a couple of weeks to arrive. I don't yet know where to power the voltage/current-display from, as it needs separate powering (DC 4.5 - 30V).

 

 

Super-interesting read, thanks for sharing (I joined recently so I'm going backwards reading :))

I have one of the same voltmeter/ammeter device, and while it works well for V,the A calibration on mine was completely off. They use a cheap metallic shunt to measure current, and you can see how they tried calibrating it by cutting a couple of slots (which is the usual process: the shunt is designed to have higher conductivity than needed, then some material is removed to get it right). Mine was over-trimmed and measured much higher than real, and had to put some solder to get it in the right ballpark. You will need to borrow a good reliable ammeter to calibrate yours, otherwise your readings will very likely be off quite a lot. 

[esaj]

I have one of the same voltmeter/ammeter device, and while it works well for V,the A calibration on mine was completely off. They use a cheap metallic shunt to measure current, and you can see how they tried calibrating it by cutting a couple of slots (which is the usual process: the shunt is designed to have higher conductivity than needed, then some material is removed to get it right). Mine was over-trimmed and measured much higher than real, and had to put some solder to get it in the right ballpark. You will need to borrow a good reliable ammeter to calibrate yours, otherwise your readings will very likely be off quite a lot. 

The display indeed does have a metallic shunt for measuring currents above 10A (or was it 20A?)... I did (try to) calibrate it with a configurable power supply of a friend, using separate power for the display (it can also power itself from the voltage-measuring side, but seemed to be more off than with separate power). We couldn't use very high amperage (the power source had no "current sink" or whatever it's called), as we had just "high power" resistors as load, maybe 3A at max, if I remember correctly, but did get the voltages & amperage to show correct values using the calibration-potentiometers in the display when testing against a multimeter (not a Fluke, but not any cheap market-multimeter either, don't remember what it was). Of course, it could still be way off in higher currents... 

The battery packs arrived yesterday, but I only got around to pick them up today, as we were moving office yesterday & today, and I got home really late (sometime after 11PM) last night, and it went somewhat late today too. I also have vee73's 14" Gotway waiting for pickup, but didn't make it today either.

So far, I haven't done much else except unpack the battery packs, and check if they would fit "out-of-the-box". No such luck, I'm going to have to cut/grind off the plastic "bumps" at the bottoms of the battery compartments and add some rubber mat between the edges and the battery lid to get a couple of millimeters of space, then it looks like the lids will fit without crowning (but the space will still be very limited depth-wise, can't put much anything to soften any hits or such in depth-direction, maybe some very thin foam plastic or such). Also, the BMS's are the kind that do not have separate charging wiring (Similar to here: http://www.batterysupports.com/60v-672v-16s-30a-16x-36v-lithium-ion-liion-lipo-battery-bms-p-274.html  but not exactly that model, only 6 mosfets and the marking seems to be "ZLA-16" instead of "ZLA-16-3", the manufacturing date on the one I saw a picture of seems to be 31.3.2015), so I'll probably add a separate smaller gauge wire coming off from the discharge wires, and add the JST there, and then solder the Andersons to the ends of the actual discharge wires, once I get the lengths right.

[robca]

I discovered the hard way that cheap shunt-based ammeter are really not that good for absolute measures: I used mine to measure power consumption between different brushless motors for drones, with different propellers: I still don't know the absolute power used by any of them, but I know, relatively speaking, which one is the most efficient and how different propellers impact efficiency (I measure both max current and max lift at different RPM, and it's easy to see which motor/propeller combination get the most lift for the least current... quite amazing how big the difference in efficiency can be between motors and propellers spinning roughly at the same speed).

I posted additional info on how to use hall sensor transducers for a much more precise ammeter in this thread: http://forum.electricunicycle.org/topic/753-currentvoltage-measurement-and-heat-dissipation/?page=2#comment-9992. I'm waiting for my ACS758 (50A and 100A, so that I can get higher res for the smaller motors) to arrive from China/Ebay to finally have a good calibrated ammeter. Unlike shunts, the ACS758 are factory calibrated

If you are assembling the battery pack yourself, I would suggest to add a couple of JST 8s connectors/wiring harnesses as well, so that in the future you can use a small external battery alarm to quickly monitor the individual cells without opening the pack

[esaj]

I posted additional info on how to use hall sensor transducers for a much more precise ammeter in this thread: http://forum.electricunicycle.org/topic/753-currentvoltage-measurement-and-heat-dissipation/?page=2#comment-9992. I'm waiting for my ACS758 (50A and 100A, so that I can get higher res for the smaller motors) to arrive from China/Ebay to finally have a good calibrated ammeter. Unlike shunts, the ACS758 are factory calibrated

I saw that, and it sounds like a lot better alternative compared to the shunt... makes me actually wonder if I should just leave out the display with the shunt.

If you are assembling the battery pack yourself, I would suggest to add a couple of JST 8s connectors/wiring harnesses as well, so that in the future you can use a small external battery alarm to quickly monitor the individual cells without opening the pack

I didn't build the packs myself, I thought better leave that to professional... I don't have anything but a cheap soldering iron and basic tools, and the cells used were untabbed, so the battery-guy had to also spot-weld the tabs on the cells himself.

I knew I had forgotten something, and today it hit me: there's a single wire coming off from the original battery, that goes to a pin in a row connector in the mainboard. Behind the board, the connector is labeled as "Input #2 (BMS)". I tore open the original package to see if it's just connected to a charge- or discharge-wire under the tape & spiral wrap, but no such luck... it goes under the BMS, to a position where I can't actually see (it's under a glued insulating plastic that's on the bottom of the BMS). No voltage coming out of it, but I did measure 5 ohms of resistance between it and the negative wire...   No idea what kind of circuitry there is, or what the wire gives out when it's connected to the wheel and it's on. It might be related to the "low battery or bad cell in battery"-warning I got the last time I tore the wheel down and built it back up, or it could have been caused by another loose connector, but I don't think I have such luck. Shit. I was a bit pissed, and this is all my own fault for not checking it earlier, but considering all the problems this project has had so far, wasn't that surprised to hit another set-back. On the other hand, @dmethvin mentioned in my teardown-topic (where I was suspecting that the wire could have something to do with the regenerative braking) that it seems it isn't needed on newer mainboards (and I might need a new mainboard soon anyway, so probably better start ordering it...):

My original battery pack had the single-wire connector that you called "regen braking" but it wasn't connected to anything. The second battery pack that I got to replace it did not have that connector at all. The controller board does not have any spare connectors, so I am not sure what is going on there. 

I did get something done today, namely finished removing the "bumps" on one side of the shell, and soldered the connectors on one battery pack.

Here's the album of the pictures I took while working, there are a few more than in this post, if anyone's interested: http://imgur.com/a/kbx9C

I cut off most of the bumps first with a Dremel-clone using a cutting disc, and then sand them down with another drill-bit on the left-side of the shell (the right side is the one housing the mainboard also):

The cutting discs are really thin and break easily, I wear eye protection, as they fly really fast and suddenly with the machine running at thousands of RPM  

The smaller bumps are actually totally unnecessary, I think they were originally meant for the black round parts outside the shell, but then someone figured putting a screw there might be a bad idea (cell puncture). The larger ones are to keep the black round part better in place, but it's already attached by 8 screws, and the bumps still work even after cutting of the excess:

After cutting & sanding the holes with the machine, I finish by hand with fine (120) sandpaper, and test to see that the black round part still fits like a glove:

That's it for the left shell-side (minus the wire channel -modifications with the electric pipe, it was getting late and I didn't want to keep my gf awake with the wet/dry-vacuum, drill and the Dremel-clone ), as I still need to cut some holes for those. 

I tested the batteries, and they still come out somewhat, but I'm fairly sure that can be remedied by cutting battery compartment lid -shaped pieces from the rubber mat that run along the edges, and lift the lids a couple of millimeters.

Also, I didn't instruct him clearly enough when I asked him to put BMS alternatively towards left and right side, but near the center line... forgot to say that the on other ones the wires should come out from the opposite end, so you can see the wires doing a 180-degree turn on the "front" (right on the picture) pack.

So, I started soldering the connectors. I'm fairly sure I asked for separate wires for discharge & charge, but the packs came with single wires. Or maybe I wasn't that clear on that. The BMS is the kind that does not have separate pads for charge-side, so in that sense it doesn't matter, but I did have to get a bit creative to get the charge wires for the JST-connector:

Not the cleanest job, but seems to work ok.

The fact that the charging- and discharging-wires are the same means that there is NO protection-diode on the BMS. Not the safest option, as I'm using male JST-RCYs on the battery side of the charging wires...  So the charge-port will actually be LIVE all the time, giving out the voltage of the batteries (so on the other hand, it could potentially be used to power other devices). I tested this with the Charge Doctor, and yes indeed, it does power from the charge port:

 

Hopefully I'll have the time to finish the other shell-half tomorrow and then put the piping into the shells & solder the connectors for the two more packs.

Edit: Oh right, I also picked up vee73's Gotway MCM2s today, but haven't yet ridden a single meter on it. That's on my todo-list for the weekend also, as I need to get cracking with the app now that I have a wheel to test it with. Plus I promised to make a version for him that gives vibration alerts just before the shutdown of the MSuper high speed -version...

[esaj]

Well, I worked on the app for the friday-night, and only managed to solder the rest of the battery connectors yesterday (saturday). Today I decided to use most of my time just for the battery-project, but didn't get that much done in the end... I took lots of pictures, but threw most of them away, as they weren't that interesting (don't know if the rest are really either ), the album's here: http://imgur.com/a/SsByW  I won't embed all the images here to keep the thread page at least a bit lighter for slower connections.

With all the burning rings I've had to hop through with this, I stronly suggest you don't try a similar project on a wheel that has very tight battery compartments, and where the mainboard and battery compartments can only be accessed from the inside   This thing's driving me mad at times...

I began by cutting holes in the left-side of the shells for the single pipe connecting the battery compartments. Also made another pipe for the channel running to the front of the wheel, but after a couple of tries I still didn't get the length & angles correct... then just took the best attempt, as it was the kind I could easily seal despite the angles being a bit (ok, more than a bit ) off, and hotglued them both.

I actually had to enlarge the holes on the compartments a bit to the same size as the pipe, as the Anderson-connectors & wiring wouldn't fit through otherwise. After getting back, I tried to put both the batteries in. The left-side went ok, got the Andersons & wiring through, and through the front-side pipe too, but with the second battery, the last Anderson-connector couldn't fit through with 3 * 16AWG wires already going through it... Yet another thing I hadn't taken into account    So I had to remove the front-side pipe, luckily hot-glue comes off pretty cleanly just by pulling hard (I didn't heat it). Well, that was some time wasted again. I did fill the old channel with hot glue on the same go though. I have to add some sort of "mud-flap" to the front channel later, maybe from the rubber mat and seal it otherwise (silicone probably). The picture is before I've tried to fit the second battery.

 

I then proceeded to cut the pieces to elevate the battery compartment lids from the rubber mat. Pretty easy and fairly fast to do using the lids to make the cuts and then cutting the inside, so that the mat is only on the edges of the compartment. I actually cut all the four pieces in succession.

Long story short: One piece of the mat wasn't enough to rise the lid on the bit thicker (left-side) battery, so I tried with two... but couldn't get them to really settle well (and it was still a bit too tight depth-wise). So, more time wasted again, with very little progress. While thinking what the hell I'm going to do now to raise the lids, I went to attic to cut a piece from a roll of plastic foam I got there, to make some cushioning for the sides inside the compartment (I don't want the batteries to fly around inside the compartments ). I also got some thinner plastic foam to put behind and front of the battery, but that's just going to make the whole thing more thicker... 

So, I was making the pieces to put around the battery, and thinking what I could do with the lids... could I somehow scrape the middles to be deeper? The lids aren't that thick anyway... My cousin has a cheap 3d-printer, maybe I could design lids with recesses instead... Carve from wood? Don't really have the tools, plus getting it correctly sized by hand would be a pain in the ass, especially as the pedal frame sits really tight between the compartments. If I only had something that was easy to cut into shape, and kept it shape pretty well... styrofoam? The thickness and size would have to be pretty good match there too, as it really doesn't bend or compress much...

So, while thinking this, I was holding the piece of of the plastic foam on my hand. I swear, if someone would have been in the room with me, they'd seen a bulb light up above the top of my head. I have something like three square meters of the plastic foam up in the attic. It's about 9mm thick, but compresses to roughly half that size (although compressing it that much is going to put a lot of stress on the plastic threads of the screw holes). It's easy to cut with a hobby knife, or scissors, or whatever, and at least somewhat malleable.

So, I got a another piece of it, cut a roughly the compartment sized piece, drilled holes using the lid as a guide and screwed the lid on top of the compartment with the plastic foam under it:

I then cut it with a knife across the edges, halved it by compressing it between two battery lids, and cut the middle part open with scissors. The result was two pieces of foam to place on the battery compartments:

Well, it turned out halving the foam made it too thin for the thickest battery pack. So I did another piece, and this time didn't halve it, just compressed it somewhat by tightening the screws.And the battery fitted fairly easily. I could actually add the thinner foam for padding behind and on top of it. Then came the moment of truth: Is the battery lid too near to the tire, ie. is the tire going to hit it? Only one way to find out. I screwed the half on to the pedal frame/motor/tire -set and...

It fits! Not that there's too much of space left, but enough that tire won't hit it at any point (yes, I did make sure the tire can make full round without hitting the lid ). I think there's one lid somewhere (maybe it's on the motherboard shell-half) that had less clearing between the lid and the tire, hopefully I can get away with thinner foam there...

I then proceeded to add the other battery similarly, as there's more wiring running through the compartment there, I made a groove in the uppermost padding to run the wires through:

And there we have it. At this point I decided to call it quits for the day, as I had been on it most of the day, and I originally thought I'd finish the entire side during the day easiily...   (this is supposed to be the "easier" side, as the other side has the motherboard, two more wire-pipes, I have to decide where to put the shunt, if I put it at all etc). On this side, I have to cut the "raising"-part for the other lid, close it up and then seal the compartments with silicone from the outside (I don't trust the plastic foam to keep the water out). Also make the mud-flap & sealing for the front wire-channel. But then this side should finally be finished, but can't say I'll be on halfway even then, as the other side requires more work...

After all this it can still turn out that the old mainboard is that picky about the BMS-input, and will refuse to work with the batteries. I'm still holding very slim hope of that not happening, and that I won't have to order a new mainboard at least just yet... I suspect that even if I ordered it right now, it'd take so long to arrive that I wouldn't have much time to ride before it gets too cold anyway . Although, as Murphy's law seems to work so well with this project, if I order it, the winter will come early, and if I don't (yet), it will come much later... but just in time with the board  

I did mail one store selling Firewheels in Germany earlier this week, in case they'd sell spare parts (or entire wheels without batteries), but haven't got any response yet... At least the board would probably arrive a lot quicker, if they do sell those (assuming they'd have one ready to go, and not having to order it themselves from the factory). I asked another German store earlier this summer (before I even had any problems, mainly for getting spare parts AHEAD OF TIME), but they never answered, not even to say "Sorry, we don't have/sell such items".   Well, keep your jack, if my money's not good...

[OleTC]

What a challenge You're up to here.

Come to think of it - how does Firewheel factory make the factory batterypacks fit in the Spaces of the 680 Wh model? Other BMS-boards?

Good Work!

[esaj]

What a challenge You're up to here.

Come to think of it - how does Firewheel factory make the factory batterypacks fit in the Spaces of the 680 Wh model? Other BMS-boards?

Good Work!

Thanks, had I known beforehand what sort of a hassle the entire project would become, I would have probably thought about it twice  

The original batteries have single BMS-board, no matter whether it's 1 (F132), 2 (F260) or 4 packs (F520 and F779). The BMS-board is pretty small and fairly center of the pack, pretty much on top of the deepest portion of the battery. The battery lid actually crowns a bit even with the original batteries (at least on the compartment containing the pack with BMS)! I think they wanted to save on costs or something, and hence the single BMS, but it also means that the packs cannot be separated, and they are actually 2 * 8S2P (F260) or 4 * 4S4P (F520 & F779), meaning a heck of a lot of wiring going back and forth between the packs, and the whole thing can break easier than single packs    

I could have gotten the 696Wh F779 packs (with shipping & customs) for about the same price I paid for these packs, but having seen the "quality" (like badly soldered wires), and the fake claim of 779Wh, I thought better to get custom packs... I was aware the space was going to be tight, but hoped it wouldn't have been this tight    I can't really blame the guy who built them, as he had to work under a few measurements I sent him and a bunch of pictures, not exactly the easiest way to figure what would fit and what would not.

And as I've mentioned a couple times before, the whole thing can still fall down on the mainboard requiring the BMS input, whatever that is... will see once I get the mainboard & other parts put back and test turning it on, if it allows me to use them or starts complaining about "Battery low or bad cell in battery"   What I'm planning to do is test that before I put the third pack into the motherboard-side (I don't have the 4th pack yet) or seal the other two packs, and if it won't work, I'll put the original 2 packs back, until I get a new mainboard.

[esaj]

Meh, looks like I'm not going to get the batteries into use without a new mainboard. I was using this super-safe method of testing the wheel with the old battery:

I actually found out a new error message (something about motor hall-sensors), as I first tried without the motor attached. Actually, I only needed to attach the hall-sensor wires, and then it would start complaining about the "low battery or blahblablabh in battery" (I'm not sure if she says "some dead cell" or "some problem with" or something along those lines)... With the red wire attached, it starts up normally (well, as "normally" as it can in that state... ).

Anyway, it is now clear that the mainboard won't co-operate without whatever magical voltage, digital data or love letters it is getting through that one red wire. The wire ends up UNDER the BMS, not on the top-side under the heatsink, like the charging & discharing wires. Couldn't really see where it goes, there's some sort of plastic glued under the PCB, and it's really tight... didn't try to rip it off by force (yet). I did measure 5ohms of resistance between the one wire and the negative discharge wire, but that doesn't help much. Even if I saw exactly where it goes, I'm not that sure if that would actually help, as I suspect there's something else than just a resistor there between the discharge wire and the red wire.

The icing on the cake is that as the heads of a couple of screws holding the BMS heatsink in place had worn out so badly that I couldn't open them with a screwdriver anymore, I decided to just drill off the heads to get a better look... So I can't attach the heatsink back either without re-threading those   And of course, in hindsight, I could have seen what I saw just from vee's old pictures anyway:

Yup, that's the one... the thinner red bastard going between the PCB and the brownish/yellowish/whatever color (I'm somewhat colorblind btw) is that thin plastic underneath it. No way to tell where it ends just from this, but like I said, knowing the exact location probably wouldn't really help me that much anyway.

[Tilmann]

Hi @esaj, I just found the fb page of some German folks who build custom battery packs for FWs: https://www.facebook.com/1radwerkstatt?fref=nf

I posted a reference to this thread on their page and asked (in German), whether they could help with some advice...

[esaj]

Hi @esaj, I just found the fb page of some German folks who build custom battery packs for FWs: https://www.facebook.com/1radwerkstatt?fref=nf

I posted a reference to this thread on their page and asked (in German), whether they could help with some advice...

Thanks, any and all help is very welcome.  I was playing around with the idea of using the old battery pack with two new packs in parallel (so the old pack could give the mainboard whatever it wants), but on second thought, it might not be the best idea to mix packs with different capacity and cells... I emailed Firewheel directly yesterday about buying a new mainboard, but haven't heard back yet, also http://scooterhelden.de/ never responded about spare parts or entire wheel without batteries (I left them a message through their contact form last thursday/friday -night, so doubt they're going to answer). Or then the contact form doesn't even work   I could still try mailing them directly...