"First Cell Group...?"

bobbill

100 W
Joined
Apr 9, 2018
Messages
256
Location
SE MN (Winona) USA
I am a ebike "newbie" and have some very basic suppositions but no definitive ideas. One of these is the oft reference, in BMS installs, to a "first battery group." Depending on the BMS, extra wire is attached to "negative of first battery group." Fairly simple...' From that and more, seems first or last group is arbitrary. Which means to me that the sequencing of the wires like the groupings, is as arbitrary.

Is that right? If so, then how does one interpret the information on a BMS diagram...say B10...B1, aside from fact the "balance" wires must be ordered 1,2, 3, 4...etc?

Seems to me might be good to be consistent to do each pack same way...so wires to motor extend from opposite poles of last group. or negative of first group and positive of last group...still not sure of that either.

So, being consistent here is mandatory.
 
If you have a multimeter, set it to test conductivity and check that the pin for B1 is connected to B- (it shouldn't be). That will answer your query.
 
To me, the actual wiring is consistent. It's just the labels that are not. Some makers start with B0 and others start with B1. You have to run the wires sequentially from the first series group to the last.

For example, a 13S BMS has thirteen voltage compare circuits, which are stacked on top of each other. Thus, you have to wire them in sequence. Hook them up in any order, and bad stuff happens. It's obvious if you were to look at a battery cell diagram that actually shows what's inside the BMS circuit blocks.

Edit: If you don't own a multimeter, or don't know how to use one, you probably should avoid building batteries,
 
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