bypassing battery heat sensor - YESA LiFePO4

[cerewa]

my LiFePO4 battery's BMS came with a heat sensor, which broke. This is a YESA pack I bought on Ebay.

Here's the deal. My multimeter shows that the wires for the heat sensor are at about 5.8V when they're disconnected. The BMS seems to be cutting power off with the heat sensor disconnected, whether the heat sensor wires are shorted or disconnected. I think the current I measured when the heat sensor wires are shorted was 25mA or so.

Turns out that YESA says the sensor is KSD9700 65degree 5amp 250V. Not sure how to bypass it though.

 

[v_tach]

The temp sensor is a thermistor. They don't usually fail unless physically damaged. Once you figure out the specs, they are very inexpensive to replace but it sounds like it might be a problem elsewhere on the board.

 

[cerewa]

What I can't figure out for sure is whether the heat sensor is supposed to show almost-zero resistance when the temperature is below the cutoff (which is 65 degrees C).

The sensor makes a little bit of a rattling noise if shaken, and the bike was cutting out at temperatures above 90 degrees earlier, but working fine under power if it was in the shade. That's what made me guess it was the heat sensor. So I think it's possible that it's a problem in the motor circuit board, maybe even with the motor's heat sensor. I'm also wondering if maybe some of the grease I put in is causing a temperature sensitive short. The overcurrent protection circuit in the BMS may be going off or (if there is one) an overcurrent protection circuit in the Cyclone motor's built in controller.