BMS shunting

[dmethvin]

@DBr You are not bothering me at all! I have been traveling the past week and waiting for bad weather so I could have an excuse to take the wheel apart. At the moment I have not shunted the F260 pack that I ride with and just being careful. I have a second 260Wh pack, the one that I took pictures of about a week ago, that needs some rebuilding and shunting. Now that I know I only need to shunt one pack I can do the one I have already opened up, but I still have to move the display board into the control board area to make room for the new pack. I expect it to take a few days to get all the work done. At this point there is no hurry though, we just got 30 inches (76cm) of snow and they haven't cleared the roads so I won't be riding for a while.

When I get home tomorrow I should have the parts I need including new blue shrink for the battery pack, some thick wire for shunting, battery connectors, a better soldering iron, and a 5A charger similar to the one @Cranium bought. I will take a lot of pictures during the process.

[DBr]

@esaj Thx for the firewheel contact and the 1RadWerkstatt hint. I had a nice and informative phone call with 1RadWerkstatt today. Even I don't know the exact function of this extra wire coming from the BMS to the PCB, I suppose now its used to provide some diagnostic info to the PCB. As hobby16 assumed as well.
I discovered from the thread "Firewheel custom battery pack" (which was hard to find ) , that you have exchanged (but not totally finalized yet) your battery packs incl. BMS to a custom build version. But I didn't understand if you have now a shunted BMSs or well designed BMSs, where power cut off during normal riding operation not happened. 

@dmethvin Currently I'm not totally sure, if shunting of only one BMS is sufficient, as asked in my last post.
In any case, I get more and more convinced to insert one (after the Y-wire with the XT60 plugs) or two fuses (before Y-wire with XT60 plugs, so for each of the two battery packs separately) into the battery output wire to have a final protection, if a shot circuit inside the PCB, wiring or motor occurs.
My idea is to use the space around the non used speaker holes, to get access from outside to the fuse(s) without disassembling of the whole unit.

[esaj]

3 hours ago, DBr said:

@esaj Thx for the firewheel contact and the 1RadWerkstatt hint. I had a nice and informative phone call with 1RadWerkstatt today. Even I don't know the exact function of this extra wire coming from the BMS to the PCB, I suppose now its used to provide some diagnostic info to the PCB. As hobby16 assumed as well.
I discovered from the thread "Firewheel custom battery pack" (which was hard to find ) , that you have exchanged (but not totally finalized yet) your battery packs incl. BMS to a custom build version. But I didn't understand if you have now a shunted BMSs or well designed BMSs, where power cut off during normal riding operation not happened. 

I ordered new BMSs from 1RadWerkstatt, that have low overdischarge voltage (2.5V), so I don't think I need to shunt these. The BMSs haven't yet been replaced in the custom packs (I'll send them to the company that built them for exchange, I don't want to loose the warranty + the balance cabling needs to be changed due to different connectors). I've used the packs with the "bad" BMSs with the custom frame though, just have to be very careful not to charge them too high    

[DBr]

26 minutes ago, esaj said:

 I've used the packs with the "bad" BMSs with the custom frame though, just have to be very careful not to charge them too high    

Sorry, but my English is not the best.  I understand:
You have used until now the new customized battery packs with the old (original Firewheel) BMS, correct?
If yes, is this old BMS shunted?
If not, did you had any cut off, due to the BMS and why it isn't shunted?

[esaj]

Just now, DBr said:

Sorry, but my English is not the best.  I understand:
You have used until now the new customized battery packs with the old (original Firewheel) BMS, correct?
If yes, is this old BMS shunted?
If not, did you had any cut off, due to the BMS and why it isn't shunted?

Oh, sorry, I'll try to explain better:

My original Firewheel F260 battery packs (16S2P) have their only BMS shunted. No cutouts, ever.

I had four custom packs made (4 * 16S1P), but they came with the wrong kind of BMSs, that suffer from overCHARGE cutout when braking with full batteries (the charging and discharging occur over the same wires). Those BMSs are not shunted, but have to be replaced due to the cutout-problem. Furthermore, shunting them would be pretty dangerous because that would bypass the overcharge protection during charging also.

I have new BMSs that are to be replaced into the custom packs. I do not plan to shunt these, as the overDISCHARGE voltage is so low that I shouldn't be able to hit it with 4 packs sharing the load (much less voltage sag).

Does this make sense?

[DBr]

@esajThank you for explaining again. Now I got it. And yes, it make sense as long the overDISCHARGE voltage threshold of 2.5V will be not reached while riding. And if I remember correctly there is also a overDISCHARGE voltage supervision implemented at the main board, wich gives a acoustic / voice waring and shaking of the unit at the end. But this main board supervision can measure the total voltage only, not the voltage of every cell. That we have to consider.
So if one cell gets weak or damaged, could this lead to a overDISCHARGE cut off of the package?
But you have at least two or even four battery packages in parallel. So this configuration should be (somehow) save.
I'm asking myself, how to detect, if one of n BMS cuts off? And what is the consequnce?

Btw. in my F528 I have two original battery packs. Each pack has two 'half packs' with 8 cells.
Do you have the same set-up with your costumized batteries or do you have four individual packs, each 16 cells?

[esaj]

18 minutes ago, DBr said:

@esajThank you for explaining again. Now I got it. And yes, it make sense as long the overDISCHARGE voltage threshold of 2.5V will be not reached while riding. And if I remember correctly there is also a overDISCHARGE voltage supervision implemented at the main board, wich gives a acoustic / voice waring and shaking of the unit at the end.

Yes, so far my testing has indicated that (at least with the older revision of the mainboard), the mainboard gives you the "Power is low" (or is it "battery is low"?) -warning when the voltage drops to somewhere around 46-48V or so. That's still around 2.9V per cell (assuming they're balanced, ie. at the same voltage).

 

18 minutes ago, DBr said:

But this main board supervision can measure the total voltage only, not the voltage of every cell. That we have to consider.
So if one cell gets weak or damaged, could this lead to a overDISCHARGE cut off of the package?

I cannot tell, I don't know whether the BMSs actually measure each cell for this protection, or only the total voltage. It could be possible that a single cell dropping below the overdischarge voltage could cause the protection to kick in. Probably someone who really understands the BMS electronics knows better. @zlymex: Do you know if the overdischarge protections usually react to single cells?

 

18 minutes ago, DBr said:

But you have at least two or even four battery packages in parallel. So this configuration should be (somehow) save.
I'm asking myself, how to detect, if one of n BMS cuts off? And what is the consequnce?

If the other two packs still give power normally, you maybe won't even notice, but I'm not sure. In the worst case, all the load dropping to the two remaining packs could also cause them to fail (if the current becomes too high for example).

 

18 minutes ago, DBr said:

Btw. in my F528 I have two original battery packs. Each pack has two 'half packs' with 8 cells.
Do you have the same set-up with your costumized batteries or do you have four individual packs, each 16 cells?

The customized packs are all individual packs (16S1P, each has their own connectors and BMS). The original Firewheel packs I have are similar to yours (2 packs in series with 8S2P each).

[zlymex]

4 minutes ago, esaj said:

I cannot tell, I don't know whether the BMSs actually measure each cell for this protection, or only the total voltage. It could be possible that a single cell dropping below the overdischarge voltage could cause the protection to kick in. Probably someone who really understands the BMS electronics knows better. @zlymex: Do you know if the overdischarge protections usually react to single cells?

Yes, if any cell reaches 2.8V(say), it will trigger the discharge protection of the BMS. However, how an actual BMS behaves upon this trigger depends on EUC brands/makers:
---- for many EUCs with separate battery packs with BMS, one 'low voltage cell' will trigger the protection and hence power shut down
---- for Gotway models, there is no discharge protection at all, nothing will be triggered if one-cell-voltage become too low or even negative.
---- for EUCs with BMS shunted, same thing as above. Since the shunted MOSFET already got the turn-off signal, better to trigger an audible or/and visual alarm.
---- for IPS(not too old models), BMS just tell the MPU to raise the pedals and flashes the red LED(no shut down) because the BMS is integrated into the mainboard.

On 2016/1/10 at 1:57 AM, esaj said:

The shunting has its bad sides. You are bypassing ALL the discharge-side protections (overdischarge/low voltage, overcurrent, short circuit), which means the BMS will not cut power in case of a short-circuit (very bad),

That right. This is why I think it's a good idea to put a proper fuse as Kingsong people do.

[DBr]

14 minutes ago, zlymex said:

Yes, if any cell reaches 2.8V(say), it will trigger the discharge protection of the BMS. However, how an actual BMS behaves upon this trigger depends on EUC brands/makers:
---- for many EUCs with separate battery packs with BMS, one 'low voltage cell' will trigger the protection and hence power shut down
---- for Gotway models, there is no discharge protection at all, nothing will be triggered if one-cell-voltage become too low or even negative.
---- for EUCs with BMS shunted, same thing as above. Since the shunted MOSFET already got the turn-off signal, better to trigger an audible or/and visual alarm.
---- for IPS(not too old models), BMS just tell the MPU to raise the pedals and flashes the red LED(no shut down) because the BMS is integrated into the mainboard.

The IPS over discharge protection philosophy seems to me the best. You are forced to slow / climb down and you get an visible indication why the unit forces you to slow down / stop. No faceplant by an unexpected cut off. An additional optional audio indication would be the optimum, from my point of view.

23 minutes ago, zlymex said:

That right. This is why I think it's a good idea to put a proper fuse as Kingsong people do.

Also from my point of view proper rated fuses (one for each individual battery package) should be put in case of a short-circuit independent of the used BMS and if shunted or not.

[zlymex]

8 hours ago, DBr said:

The IPS over discharge protection philosophy seems to me the best.

Yes, but with added complexity and cost. There are 19 wires from the battery pack to the mainboard through two connectors. It also make multi-packs(parallel packs) very difficult.

8 hours ago, DBr said:

Also from my point of view proper rated fuses (one for each individual battery package) should be put in case of a short-circuit independent of the used BMS and if shunted or not.

Agreed. I put a fuse for every battery pack I assembled.

[myfunwheel]

On 1/10/2016 at 9:57 AM, esaj said:

The shunting has its bad sides. You are bypassing ALL the discharge-side protections (overdischarge/low voltage, overcurrent, short circuit), which means the BMS will not cut power in case of a short-circuit (very bad), and will happily let you overdischarge the batteries (which could damage them). That being said, the Firewheel low-battery warning is actually very well made, it will activate with the voltage hitting something like 46-47V, if I remember correctly (although this was measured with a cheap voltage-display attached to the battery wires during riding, it might not be very precise). That is still around 2.9V per cell, which is still above the critical 2.5V per cell voltage. But the important thing is you should NEVER EVER even by accident short-circuit it if it's shunted (not that you should do it anyway, shunted or not ).

Here's what happened to my multimeter measurement probes when I accidentally shorted the pack (do note that at this point I had removed the shunt, and the protections were active, plus the meter has a 10A fuse): http://forum.electricunicycle.org/topic/125-external-battery/?page=2#comment-25599  (the short-lived high current burst was enough to melt/explode the metal head and weld the pieces inside the battery connector).

The "pros" of riding with a shunted pack in my case were no BMS cut-out during peak discharges (accelerating uphill etc) and no shut-down when going above 28km/h (although this problem might affect only the older mainboard-revisions, with the separate BMS-input wire coming from the pack). I've run my batteries all the way to the final "power is low"-warning multiple times (even done the testing so that I waited a while, rode again once the voltage recovered a bit, until reaching the point where it no longer recovers after waiting 5-10 minutes). No faceplants due to BMS-cut-out or mainboard shutdown in 1500+ kilometers.

Oh man, been there done that......lol it's crazy how fast those electrons heat things up huh.  I'm still shaking!! the spark was loud and scary, hope all is well.

[DBr]

Ok, shunting is done according the results of the discussion above. 
See pictures below.
Mod is finished, but not completed as planned. 
I planned to implement an additional electrical fuse supervision for both new fuses. Means: When a fuse is blown, a LED should indicate this, because the fuses are not so easy accessible. But I did not succeed in developing a set-up working as desired. It is not so easy, because both batteries are switched in parallel. So there is no potential difference  on both sides of the fuse immediately after blowing.

Fuses
Fist I would like to do the shunting both BMS with a fuse instead a simple wire. But than I changed my mind, because I would like to have a final reliable protection against a short circuit. If I do the shunting with a fuse, than it may happen that a fuse blows (caused by a short circuit) and than the BMS is in his original condition (without shunting) and will deliver current until it shuts of; if it shuts of.
Therefore I used two 30A automotive fuses, one for each battery pack, switch in the (-) path to the control board. Both fuses are in a fuse holder, which are under certain conditions accessible without dismounting the wheel.
See pictures below.

Volume control for the build-in speaker
Thanks to @dmethvin I recall the annoying loud „beep, beep, beep“ warning, if you reach the speed of about 18 km/h. He wrote that he re-uses the ‚sport/comfort‘-mode switch to control the speaker volume in two steps. Original volume and about the half of the volume. 
The riding mode is fixed to sport-mode by short-circuiting both corresponding wires.
I have done the same and used a 22 Ohm resistor (1 Watt). With this resistor the volume is  about the half.
Note: If resistor is in, the warning voice is hard to hear, at least for me.
See pictures below.

Sealing
I used a seal tape, with is used to seal a sink in a kitchen worktop, for the battery compartments and the PCB board / plate to reopen it easy agin, if needed.
To seal the cable ducts I use silicone at the side with the two battery compartments only and Prestik kneading seal on the side with the PCB compartment, because I needed a longer time to adjust everything correctly. Especially to remount the the wheel with its wiring in the first side of the shell (with the PCB). I was about to go crazy!
Prestik kneading seal remains permanently plastic and does not harden like normal window putty. I used it to seal the housing as well.
See pictures below.    

Before reassembling both housing sides together (closing the unit), I did a power on test (of cause with only one battery pack only) with some slight movements to check if everything is function as designed, incl. lights and switchable speaker volume. Everything looks fine and I close the unit.   

Noticeable problems (and happy to fixed them)
1) One battery pack was not correctly fixed with adhesive tape in the battery compartment. If I rode via a bump, I heard a ‚clok‘ sound from the unit, but I did not find the reason for that. Open the battery compartment during the mod I saw that the blue heat shrink tube was rubbed through in two places. 
I fixed it with tape and insulating material around the batteries.

2) While checking the tight fitting of the three motor connectors (blue, green, yellow) before reassembling, the yellow connector was broken! I was a soft check only. Therefore this connector was almost broken before! 
I fixed it in soldering a new connector to the wire.

During the test rides:
3) When I doing really hard braking / deceleration the unit growls noisy like „grrrrrrr“.
I didn’t notice this before. But may be I never brake that hard. 
Any explanation / idea / confirmation about this behavior?

4) When I accidentally accelerate to the max. speed mentioned below (33 km/h), the unit rises very shot the paddle very noticeable. It felt like an extra acceleration and I was scared. 
Do you as a Firewheel user have the same experience?

Successful test ride discover good OEM batteries 
Last weekend I have done two test trips on paved roads in a rural area with 40 km in total (starting with a full battery and with no charge in-between!) until I got the warning „power is low“ and the unit vibrates and forces me to climb down. No cut of at any time! It was the first time I discharge the battery until ‚the end‘. My weight is about 73 kg incl. clothing and gear. The trips end and start at the same location. I made about 110 m altitude difference per trip with some steep inclines. The average speed was about 12km/h. During the trips it was about 18 - 20 km/h, but at the end of each trip I have done some kilometers of curve and slow riding training. The max speed was 33 km/h! Speed measured by Android GPS app "Android-Tacho" . The outside temp was between 5 and 7 degrees celsius.
So all in all I’m now happy with my F528.
This distance range was ‚confirmed‘ when I recharge the battery to 100% full.
The charge doctor (of hobby16) indicated a starting voltage of 56.8 V and 67.5 V at the end with loaded 536,9 Wh!!! equivalent to 8610 mAh in 6-7 hours charging! 
Remember, it’s a Firewheel with 528 Wh.
Assuming that the charging with 2 A was completed after 4,5 hours (Battery is rated by 60 V and 8.8 Ah). After about 7 hours of charing, the charge doctor shows still 80mA of charging current. Thus in the last 2.5 hours we had about 13,5 Wh (67,5V * 0,08A * 2.5h) trickle charge with may we subtract from the total of 536 Wh. But we still have loaded 522,5 Wh into the battery. Looks like a good battery was almost empty. 

 

Pictures

BMS A and B shunting by wire

Not functional build-in fuse supervision 

Switch and resistor to control the speaker volume in two steps

Wiring between shelfs

Sealing battery compartments with seal tape

Fuse placement on left side and sealing of cable ducts with silicone

Buil-in fuse holder with 30 A automotive fuse

Sealing PCB with seal tape

Fuse placement on right side

Sealing cable duct with Prestik kneading seal from Bostik

Sealed battery compartments and PCB

Sealed fuse protection cap

Main side remounted

Sealing housing with Prestik kneading seal from Bostik

... after remounting.

...my Maya the bee 

[esaj]

13 minutes ago, DBr said:

3) When I doing really hard braking / deceleration the unit growls noisy like „grrrrrrr“.
I didn’t notice this before. But may be I never brake that hard. 
Any explanation / idea / confirmation about this behavior?

Mine does the same during strong braking, don't know if it can harm the motor..? Never really worried about that though.

 

13 minutes ago, DBr said:

4) When I accidentally accelerate to the max. speed mentioned below (33 km/h), the unit rises very shot the paddle very noticeable. It felt like an extra acceleration and I was scared. 
Do you as a Firewheel user have the same experience?

Mine has never done this, but I recall hobby16 mentioning that his does (sudden fast acceleration somewhere above 30km/h). Maybe I've just never ridden it fast enough  Although we've noticed some other differences between his and mine (probably due to my mainboard being older, so maybe slightly different firmware?)

 

13 minutes ago, DBr said:

Successful test ride discover good OEM batteries 
Last weekend I have done two test trips on paved roads in a rural area with 40 km in total (starting with a full battery and with no charge in-between!) until I got the warning „power is low“ and the unit vibrates and forces me to climb down. No cut of at any time! It was the first time I discharge the battery until ‚the end‘. My weight is about 73 kg incl. clothing and gear. The trips end and start at the same location. I made about 110 m altitude difference per trip with some steep inclines. The average speed was about 12km/h. During the trips it was about 18 - 20 km/h, but at the end of each trip I have done some kilometers of curve and slow riding training. The max speed was 33 km/h! Speed measured by Android GPS app "Android-Tacho" . The outside temp was between 5 and 7 degrees celsius.
So all in all I’m now happy with my F528.
This distance range was ‚confirmed‘ when I recharge the battery to 100% full.
The charge doctor (of hobby16) indicated a starting voltage of 56.8 V and 67.5 V at the end with loaded 536,9 Wh!!! equivalent to 8610 mAh in 6-7 hours charging! 
Remember, it’s a Firewheel with 528 Wh.
Assuming that the charging with 2 A was completed after 4,5 hours (Battery is rated by 60 V and 8.8 Ah). After about 7 hours of charing, the charge doctor shows still 80mA of charging current. Thus in the last 2.5 hours we had about 13,5 Wh (67,5V * 0,08A * 2.5h) trickle charge with may we subtract from the total of 536 Wh. But we still have loaded 522,5 Wh into the battery. Looks like a good battery was almost empty. 

I've measured something like around 270Wh (don't remember the exact number anymore) with my original 264Wh nominal batteries, and this was after around ~400 cycles, so the original cells (Sony VC3) seem very high quality.

 

[dmethvin]

1 hour ago, DBr said:

During the test rides:
3) When I doing really hard braking / deceleration the unit growls noisy like „grrrrrrr“.
I didn’t notice this before. But may be I never brake that hard. 
Any explanation / idea / confirmation about this behavior?

4) When I accidentally accelerate to the max. speed mentioned below (33 km/h), the unit rises very shot the paddle very noticeable. It felt like an extra acceleration and I was scared. 
Do you as a Firewheel user have the same experience?

 

I don't know what causes the growl but I have heard it on hard braking too.

The two high-speed falls that I have had were pretty quick and I didn't feel any tilt back before them.

The Sony batteries they used seem to be really good quality.