BMV-712 Temp reading high

[eblues]

I installed a Victron BMV-712 with the correct temp sensor about a yr ago and it has worked fine until I recently noticed the temp was indicating about 200 deg F. Everything else appears to be normal. After disconnecting and reconnecting the temp sensor fuse, the temp indication returns to where it should but slowly begins to ramp back up. After 1-2 days its indicating ~200 deg again.

I bought the monitor and sensor from different sources and have reached out to both of them but no response yet. Any suggestions or ideas?

The monitor is connected to 4 FLA batteries. Ambient temp is 60-75 and I have a remote sensor connected to a weather station monitoring battery compartment temp. Batteries feel at ambient temp to the touch.

[hclarkx]

The temperature sensor is likely a thermister. The resistance of a thermister rises with temperature or drops with temperature depending on the type of thermister (NTC or PTC). The BMV-712 measures resistance of the thermister to ascertain temperature. So it's possible there's something affecting resistance in the wiring or maybe the sensor itself. I.e., a bad connection somewhere along the line would introduce additional resistance and a high reading (PTC). In the other case, a short of some kind could do the same (NTC). I don't know what type Victron uses in the BMV-712 but I suppose it doesn't matter. It seems the problem is either a bad connection that is introducing extra resistance or a short of some kind that is pulling resistance down. So it could be a wiring problem. Or, of course, it could be a flakey sensor. I'd trace out the wiring from the BMV-712 to the sensor and if you don't see a problem, disconnect the sensor wires at the BMV-712 and put an ohmmeter across them and warm and cool the sensor, wiggle it, etc. looking for other than a nice smooth change in resistance as the temperature changes. If you don't see predictable ohm readings and the wiring looks good, suspect the sensor itself.

[eblues]

Thanks hclarkx. The wiring is simple & looks good, connections are clean. As you suggested I disconnected the sensor wiring from the shunt & connected an ohmmeter ... the resistance varied (drops w/ temp incr) smoothly while the sensor warmed & cooled. I'll check it over a day or two to see if it remains constant. If it does I'll pursue getting a new shunt under warranty.

[eblues]

Just to close this out .... a new temp sensor seems to have solved this problem.
Northern Az Wind & Sun was helpful and pretty prompt.