I ordered some small BMS’s (for balancing only) since my build is pretty cramped for room. They look great and are spec’d for exactly what I need. Good option for the space conscious builder. Specs are exactly the same for both BMS’s so I only included one.
@Jinra - you are READING my mind! I just got my 10s and 12s 80A BMS’ssss They are pretty frickin’ huge. I’d love a super small 10s and 12s BMS just for charging when i build an 18650 pack!
Any suggestions on similar small 12s BMS?
I just took a look here and looked for one with my size requirements. Here’s the page for 12s
Have you had any issues with your BMSs from Bestech? I just tried both and neither go higher than 40.7v on my 10s setup.
One time because I replaced 1 pack that got a broken wire and the new pack was too far out of balance from the rest.
I manually balanced all five packs separately with my hobby charger and it’s been fine ever since.
Hope I don’t offend
A beginers question… So you use BMS only while charging and than drawing directly from battery while riding?
@LukePL thats correct for what i understand from bms’s.
@Jinra do you know og these would Work with lipos aswell or do you know any small ones that does?
There are 2 options.
You can use a bms for charging only or for charging and discharging.
The 2nd option is the best because it protects the battery while riding as well as charging.
From what I gather, alternatively you can also draw power via the BMS (requires a high Amp output) and this can help with safety; eg. monitoring each cell in a battery pack to ensure isn’t over-discharged.
BMS - Wikipedia
I believe these BMS in discussion are for charge-only setups
damn u @Namasaki beat me 2 it
Thanks guys! As I thought… BMS used for charging only, can be smaller and cheaper. If cells are balanced while charging and I plan to use VESC so I can limit a curent, it should be quite safe system, right? I have SONY VTC5 cells and I want to build 10s4p pack to power one 6374 170KV motor.
And I read on some ebike forum that you should wait after charging because BMS is still balancing the cells. Is that true?
All my cells are 4.04-4.07v with a total charge of 40.6v on 10s. Both my 42.2v chargers won’t charge anymore than that.
Weird thing is the problem exists on both BMSs
After looking at the BMS data-sheet
Over Charge Release Voltage: 4.05V
While the number is about right, this is the release voltage and not the overcharge detection voltage (4.2 on sheet). They said they test every module before shipping so i don’t know.
The safety circuit will allow charging to take place after the
cell’s voltage drop below the overcharge release threshold.
This is just a quick google I did. Maybe somone with better BMS/Battery knowledge can help though
It does seem that may be causing problems, but i feel the release shouldn’t trigger until it gets the overcharge limit
I feel like they are really over charging… Quality is good tho (from what everyone says on the forum).
Guys, noob question here. If I have an 8s4p pack, do I need 4 BMS’s?
If not, how does it work with just one BMS and 4 ‘packs’ in parallel?
I think the problem in your case is the charger.
If your using a brick charger, I believe the charger turns itself off when it detects what it thinks is full charge.
I’m using a power supply with my bms’s and it doesn’t shut off, it just slowly reduces current to the battery until the cells are full.
I think the brick chargers, especially the cheap 2a models are just not dependable