Short term Battery storage question

djdenali

Howdy,

We have a tiny system (one panel with two batteries) in a cabin that will sit empty for a few weeks to a few months. Do we unhook the panel from the battery once it is fully charged? OR do we leave it hooked up with no load?

thanks,
dj

BB.

Re: Short term Battery storage question

In general, a fully charged flooded cell battery needs recharging about once per monht.

A fully charged AGM can go 3 months (or more) between recharges.

Hot batteries discharge faster (for every ~10C/18F over room temperature, discharges about 2x faster). For every 10C/18F below room temperature, about 1/2 the rate of discharge.

In general, if you have a decent quality solar charge controller, just leave the panels/controller connected to the battery bank and turn off/disconnect all loads. And all should be OK.

A good charge controller should have a float stage charging voltage (around 13.2 to 13.6 volts) for long term "trickle"/maintenance charging.

Simple/small charge controllers may hold voltage at ~14.2-14.5 volts--Which is a bit on the high side if the batteries are not used during storage. It can cause them to use more water (you should check electrolyte levels in flooded cell batteries about once per month, until you are sure they can last through the off season storage--You do not want the plates exposed from over charging/under watering).

You could disconnect some solar panels and reduce the panel size to about 1-2% of the battery AH capacity for charging--And then the batteries would not be over charged with an "inexpensive" charge controller (i.e., a 100 AH battery bank would be around 1-2 amp maintenance charge).

-Bill