Dry Camp Battery Life

I saw a remark about having group 24 batteries being rated at 50-some amps, which may be the issue. I wouldn't go below group 27, preferably group 29 or higher. That will give you enough amps for a full weekend on one battery. I could see a 50 amp battery (which is only good for 25 amps if you go down to 50% SOC) getting deeply discharged on day 2 with furnace use. With lead acid batteries more weight = more amps.

With two group 24's in parallel you have the capacity of a single group 31.

Sounds like a good system. Really good battery life.

it said 7.5 amps was hopefully what it was putting into the battery.. That has nothing to do with how many amps may be, or are, in the battery, and no matter how good the sun, once 80% SOC is reached, the charge rate slows WAY down, it's just a function of how FLA batteries work.

To test the battery, charge to 100% allow to sit disconnected, with no load, for 6 hours, then test voltage. This avoids testing a surface charge.

SOC = State Of Charge.

Also note if the zamp is trying to charge the dead battery, and ANYTHING else is drawing 12v, that amperage is lost to the battery... also increasing charge times.

What was the charge status of the batteries from the start? "charged on the zamp, and charged during a 2.5 hour tow" mean nothing. How much charge? 5amps? 10? 30? per hour..

The stupid monitor on the wall is useless when boondocking. You need to know the actual voltage and charge status/state. Taking a battery to the point it won't light an LED ceiling light is bad, very bad, for the battery.

There are some easily overlooked loads on the 12v.. stereo, and antenna booster, are two of the biggest. Make sure they are off, and or the fuse is pulled for max off grid happiness.

You state the zamp had you all charged back up in the morning.. not possible. maybe what you saw on the stupid monitor, but is telling you system voltage, not battery SOC status. If you really took a 12v group 24, in good health, to 8 volts or less, the zamp panel would have to be 400 watts and in perfect conditions to bring that battery to 100% SOC in a full day.

the battery is a gas tank, yours holds 58 "gallons/amps", the portable zamp panels can "pump", about 4 "gallons/amps" an hour.

We just spent 10-days camping down to 29 degrees. When temperatures dropped into the 30s we (two adults and dogs) thought the heater only came on a half dozen times (Thermostat 75 degrees). Not even an hour total. If you have a Group 24 battery in good condition that should provide about 75 amp hours. I'm guessing that the heater pulls about 5-10 amps an hour. 75 amp hours should get you through a weekend.