VGate Battery Assistant battery monitor

I'm experiencing battery drain on my auxiliary lithium battery due to the 5A cooler draw, but only on the warmest days. The 12V BMS reduces the system voltage below that which can trigger the isolator to transfer charging power to the auxiliary battery. On such very warm days, my drinks cooler is even more important, so I can apply my workaround, which is to plug my 5A battery charger into the 120V outlet, to keep the auxiliary battery charged and powering the cooler.

I found a cooler that works harder than most, cooling the interior to as much as 10C lower than ambient temp. The downside is that it draws about twice as much power as most coolers. I learned the hard way that on a hot day, it will drain the aux battery and stop working in much less than a day. I'm not sure how that correlates to the 100 Ah capacity, but such is not calibrated to the lower voltages.

The Vgate Battery Assistant is quite useful for tracking the small changes (to 2 decimal points) which indicate a net gain or drain on the aux battery. It has a voltage level logging graph, as well as an indicator to show the directional trend of battery voltage level, up or down.

 

I can hear the fan on the cooler, so I know when it's running, but to keep an eye on the cooler temperatures, I use a wireless thermometer, stuck to the dash with some sticky tape.

 

Hot today, 33C which is in the 90s I guess. The battery never lost its charge, so I think that means I have the thresholds on the isolator dialed in right.