Parasitic Drain on Solar Power System

Question

Hello. I have 3 100 amp hour AGM batteries in my HR. When I park the RV at storage, I first make sure that they are fully charged, then I connect them to a 50-watt solar panel on the roof to try to keep them charged. However, I have found that the batteries are subject to a parasitic drain of about .6 amp that I haven't been able to eliminate. Hours of sunlight are of course decreasing at this time of year. I am concerned about the parasitic drain. Is there a way to stop the drain by automatically cutting off the current and isolating the batteries when the solar panel stops charging them?  What type of device would be required?  Thanks for your wisdom.

ductape · Answer

Sounds like you think the drain is going to the solar panel? Unlikely. If it is, a diode is all you need to allow one way current flow.

Or is the parasitic drain in the house? Likely the CO or propane detectors. Do you have a whole house battery disconnect?

mexicowanderer · Answer

Charge the batteries to 100.0% full according to the manufacturer's tech info then disconnect the ground cable from the batteries.

With Denver's cool off-season temperatures I doubt you would return to batteries that have less than 97% state of charge. One of the strongest arguments for AGM is they do not self-discharge anywhere near as much as a regular battery. Just make sure they are disconnected from the chassis.

The alternative is to needlessly run equipment and run the risk of malfunction for absolutely no gain.

Like going away for the weekend and leaving the home heater at 72F so the cans of peas and ketchup don't shiver.

housted · Answer

I have a similar situation with a 5er on a permanent site. I added a disconnect switch to the battery circuit. When we leave the 5er I disconnect everything except the 50 watt solar panel. There is a solar controller in the charge circuit. This has worked really well for 2 years. Winter and summer.

Housted

bfl13 · Answer

You must have a shunt to know those amp numbers. That means you cannot just disconnect the batts and still have solar.

+For storage, you must disconnect the shunt to batt neg post wire, disconnect the solar neg from the other end of that shunt, and connect that solar neg to the battery neg. That will cut off all the draws from the rig and you still get solar. Put it back the other way for going camping.

2oldman · Answer

Son of Norway wrote:I connect them to a 50-watt solar panel on the roof to try to keep them charged. No controller?

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Parasitic Drain on Solar Power System

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