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DBr

BMS shunting

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I have a Firewheel F528, purchased in Sept. 2015 in Germany. About the version, I have no idea, but it has the switch for comfort/sport mode. No electric modifications were made so far. So the BMS isn't shunted yet.

Where Do I get the information about a certain version? Are there any indications about?

I rode about 260 km until now, without any noticeable problems. But I try to ride it 'carefully', since I read from the BMS power cut off. Thus no extreme running conditions. That means no extreme / fast uphill rides, no speeds faster than 28km/h (voice waring "take care, take care, ...) an I try to keep the battery capacity over 20%. The lowest battery charge I rode, was 10% and I had no limitations in riding nor warning from the unit.

Coming to the speeds.
I can fully confirm esajs statement about the speeds and the resulting warnings, but measured multiple times by an app for my mobile phone, called "Android-Tacho".
The second warning (after the 18km/h 'beep, beep, beep') is the voice waring "You are speeding“ at about 24km/h.
The final voice warning "Take care, take care" comes at about 28km/h.
When I hear this warning and it is in most cases quite hard to hear it, because it is very quit comparing to the environment / wind (airstream) noises, I immediately slow down a bit because I fear to have an accident by BMS power cut of. :-(

BMS shunting.
I know, this is not the topic of this threat, but I like to discuss about this issue to make fast riding with my fire wheel more save. 
The season time for modification is optimal now. Outside it is cold and wett. 
On the other hand I'm not sure if the shunting of the BMS has only pros. 
What about a problem in the unit witch causes a short circuit and the BMS does not shut off the power? -> The Unit will start to burn!
I'm open for discussion and hope to find the optimal solution at least for me and my be some other user as well. 

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Ya, I have done a lot of reading on this but it would seem there are not as many firewheel owners as Airwheel or Ninebot and I haven't found out yet how easy it is to shunt this unit or if it is even worth it. I have only had one shut down and it was on a low battery going up a steep hill. I'm about 90kg so I'm sure it was bound to happen. I do know that I feel a push back after the beep beep beep that comes at about 20km/hr but truthfully haven't tried to "push through it". If I didn't have a bunch of snow on the ground here in Canada, I might go try. 

Edited by Aquaneo
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Sorry, I forgot to mention, that I felt / notice a very slightly tilt-back only, if so. And this at high speed only. Approx. about 28 km/h during the 3. waring step, voice says "Take care, take care". This reminds me to slow down.    

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As a compromise you could use a fuse to shunt the pack. Even though the pack may see instantaneous loads above 30 amps, a 30-amp automotive fuse should work fine because the fuse can take loads of 20% or more of its rating for sub-second times. That is what I'm planning to do once I get around to installing a second pack on my Firewheel F260.

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BMS shunting

esaj and dmethvin thank you very much for your reply. The pros mentioned by esaj combined with a fuse mentioned by dmethvin sounds also for me like a good compromise, as long I can't trust the BMS. So there will be 'worst case protection' in case of a short circuit. 

Assuming a voltage of 50V of the battery (I don't know the voltage of the B-packs) and a max. of 1500W power consumption of the motor, a 30A car fuse for the whole system seams to by sufficient. 

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But when I would like to install a car fuse to shunt the BMS, what about the regenerative braking current / power during a hard downhill ride or an emergency breaking. I assume that this current is coming from the motor 'backward' via the fuse into the battery. Correct?

If so, it would be wise to know which max. current could flow through the fuse in this case to determine the fuse rate.

Does someone of you have knowledge about or even measured the max. power consumption / current flow during acceleration and braking at a F528?
Is it possible that the regenerative braking current is higher than the current consumption during acceleration, both under extreme conditions?

Sorry for my questions, if they are already answered here in this forum. If so, please give me a hint, cause I didn't find them. 

Thank you. 

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I don't have any hard numbers but I just estimated some values. In my case I am adding a second 260Wh battery with its own BMS in parallel to the existing one, so each BMS will have a 30A fuse shunting it. (I have about a dozen 30A barrel fuses and holders so I am using what I have already.) For there to be a complete failure both BMS would have to cut out and after that both fuses would have to blow. That seems unlikely!

Here is the data sheet for the fuses I'm using, I think they are pretty typical for auto fuses: Littlefuse AGC The chart on page 7 shows even the 30A fuse will take 100A for 1/10 of a second without blowing. So if there's a short spike above 30A you should still be okay. At a 30A load and 60V you're talking about 1800 watts. The motor on even a big EUC is rated at 1000 watts, you'd need to be drawing nearly twice the motor's rated power for more than one second before it blew. Oh, and the BMS would have to cut out first.

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12 hours ago, DBr said:

But when I would like to install a car fuse to shunt the BMS, what about the regenerative braking current / power during a hard downhill ride or an emergency breaking. I assume that this current is coming from the motor 'backward' via the fuse into the battery. Correct?

Yes, it actually charges through the discharging side when the motor is charging the batteries (during braking / downhill).

Quote

If so, it would be wise to know which max. current could flow through the fuse in this case to determine the fuse rate.

Does someone of you have knowledge about or even measured the max. power consumption / current flow during acceleration and braking at a F528?
Is it possible that the regenerative braking current is higher than the current consumption during acceleration, both under extreme conditions?

I haven't got any conclusive, but I did see values above 40A during strong acceleration when I had a voltage / current-display installed in the Firewheel with the custom batteries. But, I doubt that the curent-measuring was showing right values (it was a cheapo display bought off Aliexpress, this: http://www.aliexpress.com/item/DC-Car-LED-Red-Blue-Dual-display-DC-0-100V-50A-Voltmeter-Ammeter-2in1-Voltage-Current/1684125289.html ). I doubt it's actually very precise, especially when I had nothing to calibrate it with for high currents. So likely the actual current was much lower.

On Vee's MCM2's, I did see regenerative braking spikes above 2kW during stronger braking, but it is also said that the current-measuring of Gotway shows values about twice the real rates, so likely it was "only" above 1kW.

8 hours ago, dmethvin said:

I don't have any hard numbers but I just estimated some values. In my case I am adding a second 260Wh battery with its own BMS in parallel to the existing one, so each BMS will have a 30A fuse shunting it. (I have about a dozen 30A barrel fuses and holders so I am using what I have already.) 

It will be easier here, because the current will be divided among two BMSs, so they only need to handle half the current each.

Quote

For there to be a complete failure both BMS would have to cut out and after that both fuses would have to blow. That seems unlikely!

Actually, won't it cut out only after the fuse has blown? The protections are bypassed through the fuse, once that's gone, the current will go through the protection mosfets, and if it's too high, the mosfets will cut the power. There could likely be a cascading failure once another one of those fuses blows:

  • Drawing in excess of 60A (well, that's a bit unlikely ;)) -> One or the other fuse blows
  • The BMS on which the fuse blew will likely trigger its overcurrent protection (or undervoltage protection due to voltage sag)
  • If the current draw is still high, all the load will suddenly be handled only by the second pack -> likely the fuse will blow
  • The BMS on the second pack will likely trigger its protection(s)
  • Faceplant

At least that's what I think...

 

Edited by esaj
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You're right that most of the current is probably going across the fuse during normal operation, the voltage drop across the paralleled mosfets would still be higher than the resistance drop across the fuse. I'd be interested to see how long the 40A draw lasted, it would seem like that would have been a sub-second occurrence.

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1 hour ago, dmethvin said:

You're right that most of the current is probably going across the fuse during normal operation, the voltage drop across the paralleled mosfets would still be higher than the resistance drop across the fuse. I'd be interested to see how long the 40A draw lasted, it would seem like that would have been a sub-second occurrence.

Some seconds maybe (during accelerating uphill), it updates maybe something like 3-5 times per second, it's not like I was staring at the display all the time while riding. Also I suspect it was showing much larger values than the reality was, although the packs should be able to give that much at least for a short while (tested with 3 packs, cells rated at 10A continuous / 20A max, so 30A / 60A for 3 packs, although they could probably go even higher for a short duration, the overcurrent protections in the BMSs were spec'd at 45A per BMS).

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@esaj @dmethvin on a related topic, KS have started using 40A fuses in their Wheels (presumably to protect the control-boards). I don't think I'm alone of being of the opinion that there should be no bar to a Wheel's maximum power; better that a control-board goes up in smoke at 3,500W peak than blowing a fuse at 2,600W with a 40A fuse.

Because of the non-discrete/variable power loads, even under the most demanding circumstances, we rarely see these peaks for more than a fraction of a second, is there any information on how tolerant these automotive fuses are for this pulse load?  

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13 minutes ago, Jason McNeil said:

@esaj @dmethvin on a related topic, KS have started using 40A fuses in their Wheels (presumably to protect the control-boards). I don't think I'm alone of being of the opinion that there should be no bar to a Wheel's maximum power; better that a control-board goes up in smoke at 3,500W peak than blowing a fuse at 2,600W with a 40A fuse.

Because of the non-discrete/variable power loads, even under the most demanding circumstances, we rarely see these peaks for more than a fraction of a second, is there any information on how tolerant these automotive fuses are for this pulse load?  

There's always the risk of the fuse blowing "too early". Using multiple BMSs with each having their own fuse is probably wise, also there are slow-fuses available that shouldn't blow too easily. I grabbed this table from some random (very) slow automotive fuse, the times probably vary depending on the manufacturer / fuse type:

Time-Current Characteristics
% of Rating      Opening Time Min / Max (s)
100                  360,000 s / –
135                  60 s / 1,800 s
200                    2 s / 60 s
350               0.20 s / 7 s
600             0.040 s / 1 s

These could actually be TOO slow for this use... :D

As I've understood, the fuses blow due to overheating (the fuse-wire inside will burn through at high enough amperage), so probably it won't "wear" (at least much) during pulses, only when the current is high for a long time and the fuse cannot get cooler in-between?

Edited by esaj
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28 minutes ago, Jason McNeil said:

@esaj @dmethvin on a related topic, KS have started using 40A fuses in their Wheels (presumably to protect the control-boards). I don't think I'm alone of being of the opinion that there should be no bar to a Wheel's maximum power; better that a control-board goes up in smoke at 3,500W peak than blowing a fuse at 2,600W with a 40A fuse.

Because of the non-discrete/variable power loads, even under the most demanding circumstances, we rarely see these peaks for more than a fraction of a second, is there any information on how tolerant these automotive fuses are for this pulse load?  

But in reality there is a bar to the max power, since the internal resistance of the battery and other voltage drops will prevent infinite current. I agree you don't want to have the fuse blow in normal operation, but having some sort of protection for a dead short seems like a (fire) safety thing at the very least.

The link for LittleFuse AGC fuses (page 7) shows that a 30A fuse can take a 100-amp surge for about 0.2 second and 40 amps for about 1 second. (And a 40A rated fuse should handle 100A for 0.5 second!) Of course the draw in an EUC is pretty variable so I guess you'd integrate that over some short period of time to get a nominal current draw. For my case with two battery packs and two shunted EUCs I think 30A fuses should be fine. In an automotive application I think most fuses are there primarily to avoid melting the wiring harness, which would be a really expensive problem to fix, so they tend to be generous with ratings. That's the way I'd look at these EUC fuses as well. I can't imagine the 40A KS fuses blowing even in extreme riding conditions unless there was some other failure such as a motor windings short.

Edited by dmethvin
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As the one who gave the initial discussion an other direction (away from getting Firewheel faster than 20km towards BMS shunting), I would like to ask one of the Mods to move this BMS shunting discussion to a new threat e. g. "BMS shunting" under Brand-Specific Forums/Firewheel? 
It is just an idea to find this discussion more easily later on and also for other users. What do you think?

When I read all the replies and I additional started reading the threat "Electric Unicycle's BMS problem and solution" I get more and more confused and doubtful about solution for my / our problem. Progressively I understand the complexity of the problem in general.
But does my Firewheel F528, bought in Sep. 2015 really has this problem? Good question. Until now (260km of 'careful' riding), I had no unexpected power cut off. But when I read all these posts, I fear that my Firewheel is affected as well and believe me, I don't want to test it!

Let me do a summary.

That brings me to my initial requirement first, which is rather simple:

  1. I would like to ride my Firewheel F528 without any unexpected power cut off in all riding conditions to be save in terms of a faceplant, caused by this unexpected power cut off. Unexpected means really unexpected, without any warning from the unit before. But the warning shall be noticeable AND shat provide sufficient time to slow down or stop. Protection of myself gets of cause a much higher priority than protection of the EUC and its components!
  2. I would like to have my Firewheel short circuit save. So there must be an mechanism, which is able to cut the power in the worst case, a short circuit (whatever circumstances resulting this), to prevent the unit start burning like a ticking time bomb.

What can I do to fulfill this requirements?

As a user of an already bought Firewheel (not aware of this problems before), I can buy a more save EUC or I try to optimize my Firewheel according to my abilities and knowledge. 
That's the point. I'm not a EUC specialist, even I have some education in electric and electronics but not enough to understand the proper functionality of a BMS nor of a control / main board and I have not the time to become one.

So on what I have understand, is shunting of the BMS a workaround / solution for my requirement #1.
The warning functions of the main board are stated as ok. No danger of power cut off without warnings. 
Ok so far.

Caused on requirement #2. I would like to have a / some fuse(s) instead of wires shunting my BMS(s) to provide a mechanism, which is able to cut the power in case of a short circuit inside the unit.
Of cause the fuse must have a higher rate than build in "overdischarge/low voltage, overcurrent, short circuit" BMS protection
But which fuse rate is the 'safest' one? 30A? 40A? For each BMS? Or for the whole system?
For the determination of the 'best' fuse rate we have to take into account the max. power consumption of the motor as well the max regenerative braking power in a certain time period.

That's it up to now.

Last but not least I appreciate very much your support and the detailed level of further discussion. Respect!

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Today I start to disassemble my Firewheel F528 and discovered 4 x battery packs, labeled with 60V and 8,8Ah = 528Wh, manufactured at 2015-3-24.
On two of the four battery packs I found a BMS under the blue coat. One in the left housing side (BMS B) and the other one in the right housing side (BMS A). The second battery pack (without BMS) is connected to the neighbor battery pack with a lot of cables.
Firewheel_20160120_18-22-07_disassemblin
56a00fe3c874b_Firewheel_20160120_18-23-3

Firewheel_20160120_18-53-17_disassemblin
Firewheel_20160120_19-06-06_disassemblin

But now, I'm not sure where / what to shunt. :unsure:
According hobby16 'B-' (from battery) to 'P-' (to PCB / main board) should be shunt.
But on this BMSs I can't find 'B-'. Only 'V8-B' 
@ hobby16, could you help me? 

Just for information, when I unscrewed the PCB just to check the cabling inside and because I'm curious, I found a kind of label at the main board. 
It could be interpreted as version 4.0
Firewheel_20160120_19-51-21_disassemblin

Tbc...

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...and some noticeable problems and bad quality issues!

1.) Under the right rubber leg pad I found a red and black wire with open end. Whats that for?
Measured 0.0V (zero) when wheel is turned off and -3.3V when wheel is switched on (wheel positioned vertically or horizontally doesn't matter).
See pictures below.
56a016774589d_Firewheel_20160120_17-06-5
56a0167254702_Firewheel_20160120_17-05-3

2.) Two screwing nut are 'pressed in' to hold the axis in position. Really strange design. Isn't it? 
Picture below is showing the left side.
Firewheel_20160120_17-35-40_disassemblin

3.) At the right side one of the 'holding nuts' is pressed in not correctly. It is half way in and deformed.
But it seems to be steady (at least for now, it has held for approx. 260km riding.) and I'm not able to move it in an direction with a (sledge) hammer.
Do you thing this is dangerous? If yes, what to do?
Or do you think, if it has withstood 260km, it will held forever!
See pictures below.
Firewheel_20160120_18-17-17_disassemblin
Firewheel_20160120_18-17-36_disassemblin
Firewheel_20160120_18-17-57_disassemblin

4.) Most of the housing mounting holes used to fix the 'black axis holding metal arms' with the housing are heavily damaged.
=> The holes got a lager diameter. So I doubt that there is enough material (plastic) under the screw head to tight the housing. (hope you understand, what I would like to say. It is hard to describe in english, at least for me.)
What's you experience with your housing in this matter?
Note: This is not a problem of assembling and disassembling over and over again.
That's the first time the unit is disassembled, after it was delivered by the factory!
Please refer to the pictures below.
Firewheel_20160120_17-48-18_disassemblin
Firewheel_20160120_18-21-38_disassemblin

5.) Last but not least nothing is sealed at this IP65 specified unit.
I find dirt everywhere. Even in the PCB compartment. And I didn't drove in rainy or under wet conditions, because I have read in this forum from this moisture problem.
So I have to seal everything, as some of you have already done....

 

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9 hours ago, DBr said:

Today I start to disassemble my Firewheel F528 and discovered 4 x battery packs, labeled with 60V and 8,8Ah = 528Wh, manufactured at 2015-3-24.
On two of the four battery packs I found a BMS under the blue coat. One in the left housing side (BMS B) and the other one in the right housing side (BMS A). The second battery pack (without BMS) is connected to the neighbor battery pack with a lot of cables.
 

Looks like they've changed things. Hobby16 mentioned before that the 4-pack models of Firewheel had only one BMS and awful lot of wiring going back and forth for balancing. Also the BMSs are different from what I have. Don't dare to say anything about where to shunt, as I'm not sure.

 

9 hours ago, DBr said:

Just for information, when I unscrewed the PCB just to check the cabling inside and because I'm curious, I found a kind of label at the main board. 
It could be interpreted as version 4.0
 

I have three Firewheel mainboards, but on all of them, the first number of the version is covered by a blob of glue, so I don't know how old/new they are (newest was bought around August/September if I remember correctly).

 

8 hours ago, DBr said:

...and some noticeable problems and bad quality issues!

1.) Under the right rubber leg pad I found a red and black wire with open end. Whats that for?
Measured 0.0V (zero) when wheel is turned off and -3.3V when wheel is switched on (wheel positioned vertically or horizontally doesn't matter).

I believe these wires are for calibrating the wheel, although I've never tried them.

8 hours ago, DBr said:


2.) Two screwing nut are 'pressed in' to hold the axis in position. Really strange design. Isn't it? 
3.) At the right side one of the 'holding nuts' is pressed in not correctly. It is half way in and deformed.
But it seems to be steady (at least for now, it has held for approx. 260km riding.) and I'm not able to move it in an direction with a (sledge) hammer.
Do you thing this is dangerous? If yes, what to do?
Or do you think, if it has withstood 260km, it will held forever!

My motor has the same nuts, they have held at least for over 1500km of my riding + how much ever Vee73 rode it before I bought it (probably more, 2000+km?).

 

8 hours ago, DBr said:

4.) Most of the housing mounting holes used to fix the 'black axis holding metal arms' with the housing are heavily damaged.
=> The holes got a lager diameter. So I doubt that there is enough material (plastic) under the screw head to tight the housing. (hope you understand, what I would like to say. It is hard to describe in english, at least for me.)
What's you experience with your housing in this matter?
Note: This is not a problem of assembling and disassembling over and over again.
That's the first time the unit is disassembled, after it was delivered by the factory!

 

They have held for me, although there are small fractures around the screw holes. A metal "collar" could help there or reinforce from the inside (with an aluminum bar & epoxy or such).

 

8 hours ago, DBr said:

5.) Last but not least nothing is sealed at this IP65 specified unit.
I find dirt everywhere. Even in the PCB compartment. And I didn't drove in rainy or under wet conditions, because I have read in this forum from this moisture problem.
So I have to seal everything, as some of you have already done....

Yeah, the sealing coming from factory is non-existent and the IP65-claim is a joke. Apply silicone on all the seams (battery compartments & mainboard compartment).

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Hello everybody, just a quick bonjour from Bordeaux.

Hi Esa, hope you are well, I don't forget you and our data-logging project.

@DBr, I remember  this Firewheel battery setup now : two 4P8S battery packs in series. Each pack has its own BMS (doubling your chance of sudden power shutdown and faceplanting). The design is so horribly bad I had to make a sketch of the connections to believe it (it's nearly as bad as in earlier FW528, with one BMS and the pack from the opposite half connected to the BMS by a huge bunch of wires for charge balancing) :

IMG_20151028_220732.thumb.jpg.00289ddc3e

Besides, each pack also has a polyswitch embedded between the battery cells to cut current when overheating, thus... tripling your chance of faceplanting.

You have two shunts to do (red lines) for each BMS. The polyswitch does not need to be shunted (I marked it "facultatif" = optional). But remember, if a cell overheats, it will cut the current and you are sure to faceplant, that's the nice way of Firewheel to "protect" you. The guys are insane !!! How they manage to trash such perfectly great wheel with senseless decisions is beyond me.

shunt-FW560.jpg.731d11962133ec4fef976341

As to the two lone wires, don't worry Dirk, it's for the vertical position calibration. Same system as the connector to strap on Airwheel to enter calibration mode. There must be a tutorial (for Airwheel & clones) somewhere. The wire are easily  accessible so to allow you to calibrate without dismouting everything which is always  a pain in the .ss with a Firewheel.

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8 hours ago, esaj said:

Looks like they've changed things. Hobby16 mentioned before that the 4-pack models of Firewheel had only one BMS and awful lot of wiring going back and forth for balancing. Also the BMSs are different from what I have. Don't dare to say anything about where to shunt, as I'm not sure.

 

I have three Firewheel mainboards, but on all of them, the first number of the version is covered by a blob of glue, so I don't know how old/new they are (newest was bought around August/September if I remember correctly).

 

I believe these wires are for calibrating the wheel, although I've never tried them.

My motor has the same nuts, they have held at least for over 1500km of my riding + how much ever Vee73 rode it before I bought it (probably more, 2000+km?).

 

They have held for me, although there are small fractures around the screw holes. A metal "collar" could help there or reinforce from the inside (with an aluminum bar & epoxy or such).

 

Yeah, the sealing coming from factory is non-existent and the IP65-claim is a joke. Apply silicone on all the seams (battery compartments & mainboard compartment).

The two "calibration" wires are going to rx/Tx on the mainboard. So may be for flashing/ configuration.

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On 21. Januar 2016 at 6:37 PM, hobby16 said:

@DBr, I remember  this Firewheel battery setup now : two 4P8S battery packs in series. Each pack has its own BMS (doubling your chance of sudden power shutdown and faceplanting). The design is so horribly bad I had to make a sketch of the connections to believe it (it's nearly as bad as in earlier FW528, with one BMS and the pack from the opposite half connected to the BMS by a huge bunch of wires for charge balancing) :

In generally thought, two systems switched in parallel have a higher availability than only one. Two systems switched in series have less availability than only one.
In this case the two BMS / batteries blocks are switched in parallel. => higher availability = less chance of sudden power shut down of both BMS at the same time and thus faceplanting. But of cause, if one BMS shuts down, the surviving one has to provide all needed energy and may also shut down. 
Btw. the mentioned huge bunch of wires from BMS to the second battery half block has shrink to two wires only, which are connected to a kind of BMS extension (I might have felt under the blue coat on the second battery half block).
 

On 21. Januar 2016 at 6:37 PM, hobby16 said:

Besides, each pack also has a polyswitch embedded between the battery cells to cut current when overheating, thus... tripling your chance of faceplanting.

Ok, chances of a sudden power shutdown getting higher on each BMS. 
Do you know how and where to shunt this polyswitches? 
I didn't get this on your picture.
 

On 21. Januar 2016 at 6:37 PM, hobby16 said:

You have two shunts to do (red lines) for each BMS. The polyswitch does not need to be shunted (I marked it "facultatif" = optional). But remember, if a cell overheats, it will cut the current and you are sure to faceplant, that's the nice way of Firewheel to "protect" you. The guys are insane !!! How they manage to trash such perfectly great wheel with senseless decisions is beyond me.

Thank you for this picture, but I'm not sure, if I understand correctly what to shunt. 
So the first shunt on each BMS is the 'right angle red line' (I will call it shunt#1) marked on the right side of the picture between P- and the not labeled big soldering rectangle. This is B- as I figured out by measuring the voltage (30,2V between this bid soldering and V8-B for this half block). Between B- and B+ I measured 60,4V in total for both battery half packs. Ok so far. This is in line with your bms schematics.

The second shunt on each BMS is the '|_|' one (I will call it shunt#2) marked more left on the picture between V8-B and B+. 
I'm really unsure about this shunt, because I measured a voltage drop of 30,2V between these two pins (V8-B and B+). So I was doing some more investigations (by opening more of the blue coat) and discovered that the two wires connected to this pins are coming from the second half of the battery pack and representing the main connection to it. Thus I assume doing the shunt#2 is to short-circuit the second half of the battery pack.

Below you will find a drawing from my F528 '4 battery half block system':
(I'm very sorry for the poor quality of my drawing, but I had some time constrains. Hope you can read it. If not, please ask. Thx.)
DBr_F528_battery_schema_20160122_scan.th

Resulting this drawing and taken measures, I assume to do one shunt (shunt#1) each BMS only.
What's your opinion?

An other question:
As you can see on the picture, there is a single wire (A) and (B) coming from each BMS via the main switch (to switch on / off the unit) to the main board (PCB).
Which task / function have these wires? Any Idea?
Of cause it has some thing to do with powering on / off the unit. But why using this 'extra' wire from the BMS?

The following voltages measured for (A) at BMS-A and (B) at BMS-B :

BMS-A
Between (A) and B- = 59,5V
Between (A) and B+ = -0,9V

BMS-B
Between (B) and B- = 0,9V
Between (B) and B+ = -59,5V

Edited by DBr
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On 23/1/2016 at 10:23 AM, DBr said:

Thank you for this picture, but I'm not sure, if I understand correctly what to shunt. 

So the first shunt on each BMS is the 'right angle red line' (I will call it shunt#1) marked on the right side of the picture between P- and the not labeled big soldering rectangle. This is B- as I figured out by measuring the voltage (30,2V between this bid soldering and V8-B for this half block). Between B- and B+ I measured 60,4V in total for both battery half packs. Ok so far. This is in line with your bms schematics.

The second shunt on each BMS is the '|_|' one (I will call it shunt#2) marked more left on the picture between V8-B and B+. 
I'm really unsure about this shunt, because I measured a voltage drop of 30,2V between these two pins (V8-B and B+). So I was doing some more investigations (by opening more of the blue coat) and discovered that the two wires connected to this pins are coming from the second half of the battery pack and representing the main connection to it. Thus I assume doing the shunt#2 is to short-circuit the second half of the battery pack.

Below you will find a drawing from my F528 '4 battery half block system':
(I'm very sorry for the poor quality of my drawing, but I had some time constrains. Hope you can read it. If not, please ask. Thx.)

Resulting this drawing and taken measures, I assume to do one shunt (shunt#1) each BMS only.
What's your opinion?

You are right, you don't have polyswitch in your BMS so only shunt#1 is needed. And you only need to shunt one BMS to prevent any cut-off.

Once shunted, if you want confirmation, post a picture and I'll (try to) tell you if it's ok or not. Oh I forgot to say, a Firwheeler had a problem because the wires between the two sides was pinched by the housing and some end up being cut. So be extra carreful when remounting.

BTW, I don't think you have included in your drawing the bunch of white wires between two packs of the same side. Missing information is quite hard to interpret!

 

On 23/1/2016 at 10:23 AM, DBr said:

An other question:

As you can see on the picture, there is a single wire (A) and (B) coming from each BMS via the main switch (to switch on / off the unit) to the main board (PCB).
Which task / function have these wires? Any Idea?
Of cause it has some thing to do with powering on / off the unit. But why using this 'extra' wire from the BMS?

The following voltages measured for (A) at BMS-A and (B) at BMS-B :

BMS-A
Between (A) and B- = 59,5V
Between (A) and B+ = -0,9V

BMS-B
Between (B) and B- = 0,9V
Between (B) and B+ = -59,5V

 

I don't know, sorry. It may be some diagnostic signal wire.

 

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On 24. Januar 2016 at 0:03 AM, hobby16 said:

You are right, you don't have polyswitch in your BMS so only shunt#1 is needed. And you only need to shunt one BMS to prevent any cut-off.

@hobby16, thank you for confirming the shunt#1 only.

Let's make a bit brain storming:   :)
If I keep one of the two BMS un-shunted, could this (non-shunted) BMS cut of?
If yes, how do I detect that a cut of happened? 
When I remember correctly form the BMS thread a BMS initiated cut of can be only reset by connecting the charger to the unit and charge the battery.
With other words I would keep on riding with only battery package which has the shunted BMS without a notice that the second one is cut of. Is that possible?
So if my assumption above is correct, I assume it is more save to shunt both BMS, Is't it?

On 24. Januar 2016 at 0:03 AM, hobby16 said:

Once shunted, if you want confirmation, post a picture and I'll (try to) tell you if it's ok or not. Oh I forgot to say, a Firwheeler had a problem because the wires between the two sides was pinched by the housing and some end up being cut. So be extra carreful when remounting.

Thank you also for your offer to check my shunting. Surely I will post some pictures afterwards.
Wiring: Here "Function follows form" :) Indeed there is very very little space for all the wires. Especially for the wiring to the motor. There is almost no space to put the wire bunch back in the PCB compartment. 

On 24. Januar 2016 at 0:03 AM, hobby16 said:

BTW, I don't think you have included in your drawing the bunch of white wires between two packs of the same side. Missing information is quite hard to interpret!

As I wrote in my last post, my BMS / battery version has no bunch of (white) wires between two packs of the same side. There are two wires only! A blue and a white one, as shown in the drawing. The pins are labeled A and B where these two wires are connected to. I assume that there is a kind of BMS extension on the second battery pack of the same side which takes over the balancing function.

An other thought that crossed my mind is the function of the 5th wire from the BMS via the EUC main power switch to the PCB. I called it wire A for BMS-A and B for BMS-B, as I described above. I though it could be a kind of control line to the BMS providing signal for T1 to connect through, when main switch of the EUC is switched on. The other way around, if the EUC is switched off, T1 is open = no power from the BMS to P- (if not shunted).
But this is only an assumption, because I had not the courage to switch on the EUC with a dismounted wheel and to take the necessary measurements. 
However shunting the BMS would result in permanent power to P-.
And I was asking myself, if there is a closed (standby) current when the BMS is shunted? (Of cause main power switch is off)
So first I double checked that the main power switch is off and than measured the current from the non-shunted BMS to the PCB => 0mA -> no current measurable (in mA range) with my old measurement equipment. 
Than I shunt the BMS temporaly and repeat the measurement => Again 0mA, which i have to say gives me peace of mind.
Because if some closed current measured, I had to think about a strong circuit breaker when doing the BMS shunt.
Sorry to write this thoughts down, if already discussed in the BMS thread. But I was not able up to now to go to the whole thread, but half...   

@esaj & @dmethvin,
what is your experience in shunting your Firewheel?
Do you have the same BMS than I, with five wires outgoing to the unit incl. the single one to the main switch?
Do you have experience in conversation / addressing issues with the producing company of Firewheels? Maybe a contact for me?

Hope not to bother you to much.... 

Edited by DBr

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1 hour ago, DBr said:

@esaj & @dmethvin,
what is your experience in shunting your Firewheel?
Do you have the same BMS than I, with five wires outgoing to the unit incl. the single one to the main switch?
Do you have experience in conversation / addressing issues with the producing company of Firewheels? Maybe a contact for me?

Hope not to bother you to much.... 

My BMS was shunted by the previous owner, and the BMS is different from yours (it's just a single BMS, 2 * 132Wh packs with the power & balancing cables running between them, 8S2P -configuration each). There's three wires running to the mainboard, 2 for power + 1 extra (actual reason for it is unknown, marked as "BMS Input" under the mainboard PCB). If I recall correctly, dmethvin and hobby16 don't have that 3rd wire and my never mainboard no longer has the connector for it.

The contact I've had at Firewheel was jessie@fire-wheel.com , but I never ordered anything from them, got the parts cheaper from 1RadWerkstatt :D And they (1RadWerkstatt) also gave some other good info and tips about building custom-batteries for FW, which I've agreed not to disclose (including some info related to the extra wire).

Edited by esaj

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