Originally Posted by usinvestment
Is this common? Is it recommended to hook up a battery monitor trickle charger. I can plug my RV to 120V. Just curious to what is the common recommendation.
Yes, it's common. Flooded lead-acid batteries self-discharge at a rate of about 1% per day. Higher at higher temps. So after 3 months you figure a battery will be pretty much fully discharged, and that's not taking into account any 'phantom loads' as they call them - any accessories that are wired direct that may consume minute amounts of power. Like a smoke alarm, propane sniffer, etc.
So yes, they need to be maintained with some way to keep them charged up without overcharging them or boiling the water out of the electrolyte.
Now the next issue is what to charge them with. Newer RV's seem to be getting better load centers and 'converters' of 110 to 12v and to charge batteries. Whatever is employed must charge at a voltage recommended by the battery manufacturer (14.4 for 12v deepcycle, 14.8 for 6V golf cart types) and must then taper off to a float charge of 13.2. This will fully charge a flooded wet cell without boiling the water out of it.
Some of the trickle chargers don't shut off and can overcharge. Many factory installed converters simply put out 13.4 volts all the time and never fully charge the batteries, and then boil the water out of them. That's why user manuals for many RV's say to not leave them plugged in for extended periods of time.
Solar is a whole 'nother can of worms. So first we need to figure out what kind of batteries are installed and what kind of converter/charger is in place. The recommendations can be made as to how best to remedy any deficiency.