Would love to get some pointers regarding the best BMS for my application. I am set on discharging through the bms.
Space available 150mm x 80mm x 23mm
12s3p and Vesc 6’s so 12s3p and dual 6374. so the 12s3p will be the weak link and I want to push it to its limits.
Im thinking of the following:
Fat Bestech 80A ish: http://www.bestechpower.com/444v12spcmbmspcbforli-ionli-polymerbatterypack/PCM-D596.html
Pros:
High balancing current 126 mA something something
Integrated Anti-spark switch (just need a 12v latching button)
Can certainly handle the loads
Cons:
Super fat, nogo if it is 25mm tall (is 20mm or 25mm?)
Expensive
Board has to be turned on to charge? (which means I have to turn it off after it’s fully charged every time? kinda want to just plug it in and leave until the next time I want to use the board and not have to think about it)
No breaks when fully charged? (is there a way to get around this?)
12s3p definitely on the small side if you are using VESC6’s and dual 6374. If you are set on 3p only, you technically only need a 60A discharge bms (20A per cell unless you are gona beat the hell out of your 30Qs). I am a charge only guy, and from what I’ve seen, the D596 is the go to for a discharge bms. unless you can wait and pay for a DieBieMS.
Can I ask why only 3p? Personally I would just go with focboxes if you only have 3p. 3p doesnt have the power to utilize VESC6.
Also, yes if you use a discharge bms, it will cutoff when you brake at full battery.
Uhm it’s a space thing mostly and I am way to classy to have dubble stacked battery. and it’s one of those Chinese ones that are cheaper then the focboxes. so
But what you are saying is the power bill be lacking compared to a beefier battery? not just range? can’t I just use the bull whip on the batteries I mean acceleration, short period you know. Continuous draw is it really that high?
I wouldn’t say power will be lacking but it will definitely wear out your cells quicker and more sag, which means shorter range.
Since you said you are new, I will list you the pros and cons of charge only:
Pros:
Small form factor
Cheaper
No cutoff at full battery (hurt your battery better than hurt yourself)
No current limit from your battery
No extra heat lose from Mosfets on discharge
still balance your pack at the end of charge cycle
Cons:
Need to wire it up correctly for bypass
no under voltage cutoff (can be handled by VESC)
no immediate power cutoff when a group of cells dies. (you can also just keep an eye on sudden drop in battery capacity and catch it when your battery doesnt charge fully)
I wont bypass. friends might get hold of it down the road and y leaving it on for the weekend = angry friend…
Is it enough to just lower end of charge from the factory and still use a 4.2 volt per cell charger or do I need a special charger aswell or just the charger? hum…
if you set down the over voltage limit to let´s just say 4.1V for example, the bms will only let you charge till 4.1V and again you have the same problem.
if you drive with a cell voltage of 4.1V and break your bms think you charge and want to overcharge the cell and switch of because of it.
ah it’s a home brew carbon fiber resin infusion deal with 6 compartments. single layer 4 compartments a 9 batteries each. one for bms and one for the vescs. I go diagonal aswell on the motors so it’s tight
that thing looks dope, sadly im in Europe though. uhm. but can’t you get the same stuff in a preprogramed bms though just have the factory set it and forget it?
