Noob question thread! 😀 ask your questions here!

General Discussion
4621

Better now :slight_smile: ?

4622

Ah wait my mistake, I think your diagram is fine lol. I looked too close to those balance leads and thought all the negative terminals of each battery was connected. But you will need all the positive terminals to be connected to the BMS balance leads wise.

Second, P- is for discharge only. You need to use CH- for charging and then you can either run the BMS bypassed or use it for discharge.

4623

This is how I lay out my BMS. If you don’t have a 13th balance lead then you don’t need to put a negative balance lead. -Based on my diagram displayed here, it’s a 11 pin balance lead layout. -Also it is bypassing the BMS.

Edit: my battery is 10s, also note that this is per every cell parallel group 10s%20BMS%20diagram

1 Like
4624

Yeah got all the positive wires connected :smiley:. Only one negative connected at the top that says 1-. Ah you send a scheme I will take a look!

1 Like
4625

EDIT: so I changed the scheme. So I would be good to go now right? 0 Did you know a good bms seller in EU? Dont need a really expensive one since i only need about 10A.

4626

This won’t work, it will blow the BMS. The balance wires are off-by-one.

There will either be B0 through B12 or B1 through B12 for a 12S BMS

I haven’t ever seen B-1 through B13

Look in here. This is a 2 x 5S for 10S total, but same idea

No. Not good to go

4627

Ah I assumed that there would be 12 and 13 lead BMS’s for balance wires on 12s, as my 10s BMS’s I have worked with have both 10 and 11 leads. Totally my bad.

4628

You’re right but @epster’s diagram is not right.

Also B-1 through B13 is 15 wires and I only see 13 on the photo and B0 and B1 are missing

Not paying attention to details or assuming things don’t matter is the fastest way you are going to break something very expensive and have to buy it again.

4629

So to get this clear for me. my current wiring from the batteries towards the bms (balance wires) is wrong. But the wiring for the positive and negatives from the batteries and the charge port is correct?

Edit:

I used this BMS as reference and that had 13 wires and that’s how i setup and based my scheme on. https://www.ebay.com/itm/12S-15A-Balance-Protect-Circuit-PCM-BMS-for-43-2v-44-4v-Li-ion-Li-Po-Battery-873/323217175378?hash=item4b413eb352:g:qooAAOSwNvxa2rCm:rk:1:pf:0&LH_ItemCondition=3 I think I now see the mistake I made. But I am not entirely sure because the parts you talked about B-1 through B13 and B0 through B12 and such are new to me.

4630

Sorry :sweat_smile: I will look it up next time, was on the fly till now. But from the looks of the BMS itself, there are 13 leads from the first link and then 12 from the second link to the BMS.

From your diagram @epster , based off the first 13 lead BMS, it looks fine. It’s just that you need to make sure that B-1 is connected to the bottom of the pack (negative), which is fine. This particular BMS also has a CH- unlike the other link you had first posted which is fixed in your recent diagram. All in all, to me the diagram is fine. Not sure why @b264 sees that it is wrong.

Edit: nvm I think both BMS’s have their own dedicated CH- port, it’s super unclear from just the photos on ebay lol, still all looks good though.

4631

Oh hahah Oops. This really shows how big of a ‘‘noob’’ I am at BMS`s and such. I am not quite sure what you mean with ‘‘bottom of the pack though’’.

EDIT: Oh hahah that explains. So just a quick summary for me. I will wait for others to confirm too just to be sure :grin:. If i get a 13 lead bms like a linked. That has a B1- port Thats the one that has to have the negative wire wired up the rest just in order how I wired them up. The port that says CH- is the port that I will attatch my power plug too. This is how I am supposed to do it right?

4632

You just need to make sure you are connecting the balance leads appropriately. for ex if there was 12 leads only (meaning no negative balance wire), the wires should go in series of voltage from B1 to B12. Always be safe and check with a Voltage meter. If there was a BMS layout it would have been easier lol

Edit: I busted a BMS because I had the leads the other way around and the BMS was trying to regulate the voltage backwards. It got so hot and just didn’t allow me to charge anymore. Good thing cheap BMS’s are easy to replace and do not much harm (If monitored that is).

1 Like
4633

I will keep these tips in mind! Thanks you helped a lot :smiley:

4634

Honestly you do you, some people like 13 leads, others is 12 leads. I don’t see why it matters with cheaper BMS’s. Use the BMS appropriately to the way it’s made always.

Next step is to use a better BMS to have faster balancing between cells. Cheapo ones take weeks if not months on bigger battery packs.

1 Like
4635

The other thing I see would be -There should be a fuse on the charge port, and - I’d prefer to see the loop key on the positive, rather than the negative (This isn’t as important as the fuse.)

2 Likes
4636

You want at least 80mA balance charging and not less than about 30mA

2 Likes
4637

Use this on your charge port

https://www.mouser.com/ProductDetail/576-099707.5WXN

2 Likes
4638

At which one of these specs do I have to be looking out for? If i want to have a minimum of at least 30mA image

4640

“Balance current for single cell”

4641

At least 30mA and preferabbly 80mA! Oh then I really have to buy a better BMS then these ones. :joy: