Hey there, Ive been worrying about this exact problem for a while now. I dont see how this solves the problem (although I’m happy for you that it has) as far as I know, The issue is that when the battery is full and you brake, the VESC cannot dump any current into the cells, because the BMS tells the vesc that the cells are full. Then the VESC is shutting down to protect itself. Is what you have done the following: When charging via regular wall charger, the charge goes through the BMS, this means that at a full charge, your cells are sitting at a nice happy 4.2 V BUT when you brake with your motors, they send current straight to the cells, bypassing the BMS, so the cells may get to 42.1 V or something, but at least nothing shuts down. Does the BMS not freak out at that point, telling the vesc that there’s the problem (I keep thinking of a skateboard as a community talking to each other so that I can shred the streets)
The BMS is not hooked up to the VESC so even if it shuts off power from the charger, the power is nit coming from there.
@Eboosted, I suggest you add a fuse so you don’t blow anything up now that you’re bypassing the BMS
Is the general answer to this, to under charge slightly, maybe 0.5v? Your brakes then work even right off the charger, and you get more cycle life for your cells by 1. not overcharging during braking, 2. not charging to max
@PXSS I’ll set a fuse between the battery and VESCs, unfortunately there no much space and the 80A fuse and fuse holder are extremely big.
Has anyone found a small and suitable fuse and holder for this application?
@deucesdown, if you check the charge on each cell the voltage at full charge sits between 41.6-41.00V so charging a little bit more won’t cause any issues, some people charge it until 42.5V or even 43V, cell won’t be automatically damaged, on the other hand this will be donr only for a fraction of time, I’d say between 1 and 2 minutes of riding.
Isn’t the maximum input voltage setting on the BLDC tool supposed to stop this?
I know a lot of people say to leave it at 57V to stop the vesc switching off but if you’re discharging without a BMS shouldn’t this setting stop you overcharging the battery?
Not really. That setting is meant to protect the VESC from over voltage and not the battery. Setting it at 42V would only cause the vesc to shut off sooner.
2 options are set to 57v and slightly overcharge when braking or set it to 42v and not overcharge but shut off when braking
Won’t even happen for that long. It’ll literally only happen while you are actively braking enough to charge the pack above 42v. As soon as you stop braking, the voltage should settle back down.
I rather have a 0.5% less battery cycles than loosing brakes at a street crossing
Don’t want to start a new thread as this seems to be similar to what I experienced today, but could you guys check my error log and see if this would in fact be the same issue as @Eboosted experienced?
Not sure when I received this error code as board was on for several hours, but at the beginning of the ride with full batt. I had several losses of brakes when going down a very very minor slope at almost zero speed… Had those brake cutouts a few times and avoided to go downhill and no more brake issues since.
Are you discharging through bms?
Yes. Same BMS as you had I believe. SuPower 10s 60A
You went above the 57V max input limit
Yes, and why was that /how could one avoid that?
Breaking on full battery caused it, you could increase the limit to 58. Or just be mindful when full battery
There are ony two ways to avoid this:
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Use the BMS for charging only, you will loose all battery protection features of the BMS for discharge
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Charge up to 41.5V SOC (state of charge) instead than 42v, using a custom charger or soething similar than this:
Couldn’t there be a simpler software solution to this like an option for the vesc to just disable regen braking altogether when batteries are above a certain voltage?
No option st the momentu unfortunately
In a prototype i am already trying to adjust the brake power to stay within limits. Problem is that in Eboosted’s case the result might be the same because the BMS shut’s down immediately so the power can’t go anywhere. So it doesn’t really matter if it try’s to reduce the power a little. What i have in mind is for my next 13S build. Just want to know if it is possible to do that. And there a reduced brake power is still better than no brake power. But i expect it to never touch these limits.
But long story short. Use the BMS only for charging. Or simply get rid of it and charge your cells with a external balance charger. Or don’t use any of those and check your single cells voltage every now and then and if needed charge the single pack individually so that it fit’s the others. But don’t integrate the BMS in the cycle with the VESC. It’s useless. And most times the BMS fails instead of the cells. And if the cells fail then mostly because one cell cell looses connection. And the BMS balance current can never ever compensate that.
Hi Ackmaniac, i reallywould like to talk to u. its understandable that u tell the people to bring the bms into the charge circuit. This is for pilot safety reason. the rider should have the same brake in all usecases, if full or empty battery. If battery is full and u brake, u cook ur batteries and u have less live cicle for the batteries, BUT brakeing is always the same and feels good…
But for me i really would prefer to have less brakeing power, which gets more and more braking, the more u ride and the voltage of batteries gets down. so u get way more cicles out of ur batterie.
so iam really interested in the extended super vesc, which can handle the maximum voltage for brakeing. That would be so awesome… So… how can i help u?
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