A solenoid of that size will draw in worst case and I am sure it is less, about .5 amps. Do the math. In 24 hours that is 12.5 amps. This is a very simple problem. Batteries are buckets full of marbles (amps). When batteries get old the buckets become weak and cannot hold as many marbles as when new.
It would be a very rare case that batteries would last that long in any RV. Most are gone way before that.
Load testing them is a real waste of time. We don't buy batteries, we rent them. That is to say that batteries must be replaced every few years.
If you had a solenoid bad enough to run two batteries down in one night you would have some serious smoke.
H/R Endeavor 2008
Ford F150 toad >Full Timers
Certified Senior Electronic Technician, Telecommunications Engineer, Telecommunications repair Service Center Owner, Original owner HR 2008