With solar panel charging of the second battery (in my experience) a lot depends on the ambient temperature and number of times you are opening and closing the fridge, + it depends on what size and power draw car fridge you have. In many mild climate situations a decent 60 watt solar panel will keep things running well with many car fridges. But in hot conditions and constant fridge use, as Swaggie suggests, you will need double or triple the capacity to keep things running OK. A few variables to consider!?High as a minimum.
62 amphr battery won’t give you much time especially if it’s not lithium…
Lead acid don’t like being run down all the time, my deep cycle doesn’t go below 50%.
you’ll need a inline monitor to see how many amps the compressor uses over 24hrs
I’d also suggest a 200-250 watt solar panel otherwise you’ll need to keep the motor going on the second day most likely if your not driving around.
I guess I'm about to learn something here? But I've no idea what your 'Cut-in comp on' setting is about. I'm assuming comp means 'compressor' and, in which case, it should operate in any situation where the fridge temperature is above what you have the fridge temperature set for.
Fridge is right next to the battery and I use use 25amp or thereabouts cableHigh. Cutting out at 11.1v, the battery is already well into degradation territory. I don't really like the built-in battery savers on fridges, though I understand why they're there - for those that like to plug and play. They tend to cut out too low even on high, and cut back on too low.
You're likely to run into issues if you don't run appropriate cable gauges also - voltage drop from your battery (depending on where it is) may well mean the fridge is never getting appropriate voltage for a 'high' setting once under load.
Make sure your cable runs are appropriately sized, use the length of the entire circuit (return, not just TO the device) to calculate the appropriate gauge, and test voltage at the fridge side while it's under appropriate load - not just with a multimeter on the end and nothing else.
50% state of charge is 12.05V so I would set the cut out to not be below this otherwise you will shorten you batteries life if done constantly.
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This is why so many people are going Lithium, can be taken to a much lower state of charge(80-90%) and half the weight.
The BMV712 has a configurable relay trigger to turn things off. Would need to control a separate high current relay with it though.Maybe too much information for a simple task, but if you do want to monitor your battery properly, get a shunt-based monitor like the Victron BMV712 or something. It will measure current in and current out to advise you more accurately of your battery's state of charge.
I don't know if any SoC monitors have relay outputs to cut off supply, but it'd be nice if there was something like that around.