I’m glad to know it. I’ll have to pull my packs and do some checking.
Oh, about the bit with the balance going to the positive side of the series connection, it doesn’t actually matter which side of the series connection as they are both connected together.
Essentially you should have one wire going to each side of every cell, except for you the main negative on some bmss
2 Likes
Does this help? I have added the difference in potential from B- (or B0) assuming 4.2V cell charge state.
Battery BMS ΔV
B1- B- 0
B1+ B1 4.2
B2+ B2 8.4
B3+ B3 12.6
.
.
.
B12+ B12 50.4
On the D140 you could also connect the B1- to the B0 in the BMS (since there is electrical continuity between these 2) using the balance lead but that would end up with the full charge current going through that lead.Preformatted text
It’s usually marked
B- -- 0V
B0 -- 0V (not always present)
B1 -- 4.2V
B2 -- 8.4V
B3 -- 12.6V
B4 -- 16.8V
B5 -- 21V
B6 -- 25.2V
B7 -- 29.4V
B8 -- 33.6V
B9 -- 37.8V
B10 -- 42V
B11 -- 46.2V
B12 -- 50.4V
B+ -- 50.4V (doesn't connect to BMS)
Connecting 13 balance leads to B0 through B12 allows you to charge through the balance leads without connecting B- or B+ to the BMS, in most but not all cases
If you did that, full charge current would flow through B0 and B12 and approximately 100mA maximum would flow through B1 through B11
1 Like
Functionally the only change I made was to move the B12 balance lead to the positive side of the CG12 from the negative. Is that correct? The B12 Balance lead, pack positive and charge positive are on the positive side of the CG12 now.
In your diagram you don’t have a balance lead (b11) between cell group b11 and b12.
And you have battery negative connected to b1 on the bms.
IF battery negative is supposed to be connected as a “balance lead” on your specific bms it should most probably be to b0, as the b1 should be connected inbetween cell group 1 (+) and cell group 2 (-)
2 Likes
There’s no B0 on the D140, so I assume I should move all of the balance leads to the positive side of the cell groups, correct?
If you don’t have b0, the least confusing way is to think balance lead - > positive side of cells.
As long as b1-b11 is connected between cell groups and b12 is on cell gr 12s positive side, it should be right.
3 Likes
Copy that, I think I am understanding now. Thank you so much for taking the time to explain this, not a lot of people would and I want you to know I appreciate it.
2 Likes
Any time, any day 
2 Likes
There is a B0 on the D140 image you linked above, but other ones still have it on the PCB, but the connector does not go all the way to it. It all depends on your specific unit.
1 Like
I have x5 D140’s right now, none of them have the B0 even though the image does. The image on the website still shows it but they don’t actually come with it.
It should be electrically the same as the B- pad, just lower current (aka only suitable for charging)
My D140 has a B0 on the balance connector but it is labelled B- like in the photo.
Hey are your packs in balance? I wonder how it’s doing that since the balance leads are connected to the - of the p packs. It wouldn’t know what the voltage’s of the packs would be right?
I contacted bestech specifically asking about B0 when I was assembling my pack and they told me “do not connect B0 to the negative terminal”. So I have assembled my pack according to the manufacturer specifications. it works very well and keeps I’m balance without issues.
1 Like
I checked 2 of them last night, one was built over a year ago using the previous illustration. Its still perfectly in balance. There’s no cell group more than .01 volts off from the other cell groups. I don’t know what that means, as correlation doesn’t equal causation, but I am glad it’s the case.
1 Like
Don’t fix what aint broken. 
But that’s wired. Its like if you put one end of your multimeter on ground and the other on the - of the packs.