[Caevlist] Weird little BMS

Christopher Koch jazzjunkie.chris at gmail.com
Thu Mar 8 19:12:34 PST 2018


I've got a little 60A BMS — the kind with sense/balance wires for every
cell, as well as B-, C-, and P- connections — but the datasheet and the
manufacturer's support have me totally confused.

Normally B- goes to pack negative, C- goes to charger negative, P- goes to
load negative, and pack positive is common to all.

Their support guy insists that both load and charge go to C-, leaving P-
unconnected. I have an English and a Chinese datasheet; both have a diagram
which also show P- unused. The text of the English document agrees too.

But the text of the Chinese data sheet says connect P- to load, and that
seems to be the convention everywhere else. Am I crazy to doubt what I'm
being told?

I haven't fully reverse-engineer the schematic yet, but P- is connected to
the drain pin of all twenty N-channel MOSFETs. B- is connected through
sense resistors to ten of the FETs' source pins. C- is directly connected
to the other ten's source pins.

This says to me that 10 of the mosfets are for overcharge protection, and
10 are for over-discharge protection.

Anyone have any insights?

-Chris Koch


(dictated but not read)
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