My first BMS purchase...

I want to build a small 5s1p pack and a 7s2p or 7s4p pack and want to run my BMS choices across the forum before buying... Im really new to this BMS stuff.

For the 7s pack will charge using DC-DC from my car 12v port
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/112314398195

And for the 5s pack (to run a small
Portable TS100 DC soldering iron)
Will charge with a hobby charger

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/132165834589

Thanks

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Here is another one I am looking at for a 6s pack...

https://www.ebay.com/itm/6S-8A-22-2...293477?hash=item3d48e9e665:g:hJkAAOSwm9tZvIi~

My question for this one is if I only charge it to 3.9 or 4.0 volts, will it still balance between the cells, or does that only happen at full charge?

Thanks

No it wont balance unless the cells go above 4.2V. So unless you think that is fine then go but if not you need a proper BMS or charge them up fully.
When charging with a hobby chager you dont need to worry since the RC charger can balance for you. The bms is only used for low voltage cut off in that case.

Well thats unfortunate... I though they would balance to keep the cells close to each other regardless of the voltage. What is that called usually, active balancing?

I also noticed that some of the BMS PCBs I linked are protection only, and dont offer any top end balancing.

I guess for these small packs its hard to find more full featured BMS with balancing.

At this point I might as well build JST balance leads on everything so I can check the pack and balance them if needed instead of just trusting the PCB.

For medium sized packs... say something like 7s14p , could I still use the 7s Balance BMS I linked or is that too small? What would you recommend for a project that size? Max load would be less than 10a

You could try the Chargery Power BMS8.

http://www.chargery.com/BMS8.asp

I have one but haven't had a chance to thoroughly test it yet. It does actibve balancing and for a smaller pack could be perfect

Wattsup said:

You could try the Chargery Power BMS8.

http://www.chargery.com/BMS8.asp

I have one but haven't had a chance to thoroughly test it yet. It does actibve balancing and for a smaller pack could be perfect

Click to expand...

Awesome recommendation... never knew about that.

Where does one order such a product in the US? Im searching and I dont see any vendors?

Its not the size of your pack that is the denomination its how cheap you want it to be Buy a proper BMS and all your requirements are satisfied.

There is no use in balancing in bottom and wasting energy right? Also note that at bottom the voltage can be totally different compare to the top

Passive balancing is generally when you waste energy into heat meanwhile active is where you transfer energy from 1 cell to another. Note that both can be configured to work whenever you want but generally passive are set to the top end of the charge and only when charging! This to not waste energy you dont have.

The cheap BMS systems are static and set for normal range use. If you want this to be set you need to pay more. 5-10x more in general.


The current you want to have through it is one thing. On those cheap ones you look at.... Then your max should be half of what they say is max in my world! All other can fail

The more important is the balance current. You generally say 50mA balancing current per 30Ah battery pack size.

CrimpDaddy said:

Wattsup said:

You could try the Chargery Power BMS8.

http://www.chargery.com/BMS8.asp

I have one but haven't had a chance to thoroughly test it yet. It does actibve balancing and for a smaller pack could be perfect

Click to expand...

Awesome recommendation... never knew about that.

Where does one order such a product in the US? Im searching and I dont see any vendors?

Click to expand...

I got mine from aliexpress, only took 10 days to arrive.
They have other models that look better as well

Ok... I bought one of those BMS8 units... hopefully it is decent. Ill try and do some testing and post my results.

CrimpDaddy said:

Ok... I bought one of those BMS8 units... hopefully it is decent. Ill try and do some testing and post my results.

Click to expand...

Hi
As you mention chargery bms. I had a look into it several times and gernally like it. Any experience you can share on it?

Best regards
Karl

CrimpDaddy said:

Wattsup said:

You could try the Chargery Power BMS8.

http://www.chargery.com/BMS8.asp

I have one but haven't had a chance to thoroughly test it yet. It does actibve balancing and for a smaller pack could be perfect

Click to expand...

Awesome recommendation... never knew about that.

Where does one order such a product in the US? Im searching and I dont see any vendors?

Click to expand...

Thanks as well. ordered something from there already.

Love the built in screen on the BMS16... great idea.

Charly144 said:

CrimpDaddy said:

Ok... I bought one of those BMS8 units... hopefully it is decent. Ill try and do some testing and post my results.

Click to expand...

Hi
As you mention chargery bms. I had a look into it several times and gernally like it. Any experience you can share on it?

Best regards
Karl

Click to expand...

I wish I had a more thorough report... I tinkered around with it but never really got a chance to put it to the test.Ihaven'tactually tested any of the voltage cut-off, charge/discharge protection, or anything like that.

It seems decent, I think it's a bit over-priced for what it is. It looks like a regular balance board inside a fancy case. That said, the banana jacks for input and output, JST, and a display make for a nice portable plug and play BMS. It has a high pitched wine to it, and appears to work. I don't think id consider putting anything more than 15-20 amps rms though this thing...

CrimpDaddy said:

Charly144 said:

CrimpDaddy said:

Ok... I bought one of those BMS8 units... hopefully it is decent. Ill try and do some testing and post my results.

Click to expand...

Hi
As you mention chargery bms. I had a look into it several times and gernally like it. Any experience you can share on it?

Best regards
Karl

Click to expand...

I wish I had a more thorough report... I tinkered around with it but never really got a chance to put it to the test.Ihaven'tactually tested any of the voltage cut-off, charge/discharge protection, or anything like that.

It seems decent, I think it's a bit over-priced for what it is. It looks like a regular balance board inside a fancy case. That said, the banana jacks for input and output, JST, and a display make for a nice portable plug and play BMS. It has a high pitched wine to it, and appears to work. I don't think id consider putting anything more than 15-20 amps rms though this thing...

Click to expand...

I agree!
It's a handy small project bms.

I did some testing and found the low voltage alarm and cut off work ok.
That whining noise gets old pretty quick if you have the battery nearby.
It does do active balancing but not as powerful as advertised, I don't think
I'm tempted to check out some of their other models.

I finally got around to testing... it works, but it has it's quarks.

I am using cells that are pretty out of balance... I want to test this with a larger pack to see if the voltage bounce back keeps it cycling like this since I would consider a 1.5A load somewhat high for these cells.