I was wondering. If I bypass discharge than would I need to charge the battery up to 42V in oder to allow the BMS to balance the cells? Do you charge the cells to max their max Voltage every time?
Yea you can charge to max voltage every time. The cells should balance down to about 4.18/cell. Typically even within a mile of riding you use alot more energy than regenerated during braking. So the chance of truely “over charging” the pack is slim.
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Ok I will use one charger at 41.2V for daily charging and another one time to time to balance the cell at 42V. Thx thx
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In case of bestech you can order the settings when you order the bms, or you can get a programming card to do it yourself
i do not know about other bmss since i never used them
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Do you have their software to program it?
When you order a bms you can buy the programming card from them ( some Texas instruments model) and it comes with an usb with the software
if you already have the card you could ask them for the software only
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Interesting, thanks!
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That’s interesting. I knew it that with bestech you can choose the setting before the order. I didn’t know you could have the programming card. Nice to know
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Sorry to resume this thread, but this morning I tried to replicate the problem and indeed when I tried to break hard once left my apartment the board stopped breaking again. This time I was monitoring the ride and I am not sure was the bms the problem.
As you can see the VESC went in overcharge protection. It recorded 58V spike. When I tired to break hard few kms later it was fine. So I am wondering whether it’s only the VESC the cause of it and not the bms because if I reach 58V with a spike probably when the voltage is a bit lower I do not reach the 57V threshold set in the VESC tool but for sure still higher than 42.25V overcharge protection of the BMS. Maybe the BMS has to read this overcharge for few second before cut the current while the VESC does it immidiately. Do you think can I increase the threshold to 70V on the VESC tool just to be safe? Thx
Edit: I was looking around for a solution and could be the same problem @Eboosted described to @Ackmaniac once http://www.electric-skateboard.builders/t/extended-bldc-tool-with-watt-control-mode-ppm-cruise-control-individual-throttle-curve-and-android-app/12286/702?u=rey8801 Where basically the bms stops to send current to the battery and for that reason the VESC reads higher Voltage and shows the overvoltage fault.
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Okie doke if you have bypassed the bms and that is happening one of your series connections is broke Inspect the pack @rey8801
No this morning the bms was still with the discharge connected. I just wanted to say that I could repeat the issue and present the data too. Now I am changing the bms configuration to charging only and once I charge the board I will try again to brake hard.
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Ah ok. Yea if the bms was still on discharge. The voltage spikes is from the BMS cutting current.
If this happens with bypassed, it is likely what I said in my last post, and a thorough inspection of the pack is necessary.
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Correct, the BMS is the party crasher here. Kick it out of the discharge cycle and only use it for charging.
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Thx did it this afternoon. I will report back tomorrow when I charge the board and try again to brake.
Let’s see it 
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Hello @rey8801, I know this problem like the back of my hand.
You are charging your battery at 100% 42V or close to that, when you brake the regen current raises the voltage until the point the BMS shuts the current down to the motors, at this point the current has no where to go because the line to the battery is cutted, so voltage raises until VESC shuts itself down causing a fault.
This fault does not mean the spike it’s the culprit of the issue, it’s just a consecuence of the BMS shutting power down and leaving the current flowing no where
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Yes thank you very much. I change the BMS as charge only and I am going to test it today if it is gone. Scary stuff when happens!
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What bms are you runing?
The best way to fix this issue is charging only to 41.80V, get an adjustable EOC charger
Dude I’m cracking up picturing you delivering the stone cold stunner to the pooch!! 
I am using this one 10S 40A/60A bms Li-ion large high current BMS PCM with SAME discharge port for electric bike electric car 60a bms http://s.aliexpress.com/ZzUZRVvE?fromSns=Copy to Clipboard. I do charge the board to 41.2V but the BMS still cut the current if I brake hard in the first km. Then no problem whatsoever. That’s why I didn’t have the issue before it’s really in the first km that can happen the the voltage goes down.
@Deckoz @Acido @Ackmaniac @mmaner Thx guys for the help! Now BMS is only for charging and I tested the board fully charge and I can brake hard without any issue now. Thx Thx Thx!
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