I’ve just completed my trailer conversion from the built-in converter to a Multiplus II, MPPT, Battery protect, Lynx distribution, and a Smart Dongle. The dongle does not have a hard-wired temperature sensor, just its internal version.
I have two 12V LiFePO4 batteries wired in parallel. They have a BMS, but it does not provide low temperature charging cutoff. I was intending to use the MP to manage when to stop charging. To that end, I installed the provided temperature probe to one of the negative battery terminals. The smart dongle is inches away.
From what I have read, the MP prefers the hard wired temperature setting for temperature cutoff when present, and this appears to be correct. The problem I’m having is that the probe and the dongle disagree about the current temperature, and not by a small amount. The dongle shows a temperature about 10 degrees C above the probe. I took a thermometer to the battery terminal, and it appears that the dongle is pretty close to actual temperature, while the probe is reading much too low.
Is this common?