Small Bestech BMSs!

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

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Size-wise these look pretty manageable

Whatever you choose make sure theres a value for “balance”, some don’t have balancing.

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Hmm @Namasaki,

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 :thinking: Enertion bms

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

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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? thanks Luke

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

Maybe this?

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.

Overcharge Release 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