10S bestech bms without balance wires - weird behaviour

Hi, I’m in the middle of a build,

using HCX-D223 10S-80A BMS I didn’t connect balance wires yet… I’m trying to use it to charge the battery and as an e-switch only for now.

two questions,

  1. during charging, it’s main heat sink is getting very hot (about 70-80 degrees Celsius) - is this normal?

  2. it’s e-switch is on, but output gives me some weird voltage, 28ish volts and falling as I’m measuring, as if I’m measuring a small capacitor. battery voltage is in the normal range, 38-ish volts

I’d expect balance wires to become relevant when battery is fully charged, but is the whole device behaving weird because balance wires are not connected?


far as I know, that’s a good way to destroy a BMS and possibly your batteries – you don’t charge a li-ion or li-poly pack without balancing.

that’s not correct, especially short term (I’m in a middle of the build) and if not maximally charging and discharging

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okay – I’ll agree that one can treat the batteries like that and get away with it.

what about the BMS? I don’t think they would do well, dumping the current through without the leads attached. the BMS would be thinking all the cells are at 0

Just to answer and close this,

everything is ok after balance wires are connected, which, in retrospect is kinda expectable given + line never goes to the BMS otherwise :smiley:

Main heatsink does get hot still, I suppose it’s controlling the voltage through resistance, so that’s expected I guess.

(for wiring reference)