Battery Question

SouthAfrica75

Have a set-up of 2 x 105 amp batteries to a power inverter.

This is my power back-up in the event of a Hurricane here in South Florida.

My question is... the probability of using the system every year is slim. So should I just let them sit and do a top off charge if we are under the gun for a hurricane or should I run somthing like once a month and recharge.....

They sit outside with high heat and humidity during the summer in a closet

Solar Guppy

Re: Battery Question

Heat and No charging will equal dead batterys for sure

You need to have tempature compensated float charging and I would suggest you keep them inside, nothing kills batterys faster than heat, and outside in a closet I'd bet its 120+ in South Florida

niel

Re: Battery Question

i would also lean to use them occasionally so that you can verify they are in good working order.

BB.

Re: Battery Question

I tried to post this earlier when the board went down... It repeats what was said above with a little more information.

Depends on what type of battery charger you have...

If you have a good temperature compensated charger that can keep the battery at float charge voltage level (see Wind-Sun's Battery FAQ), then just leave it plugged in and all should be good.

If, however, you have a battery charger that does not keep a stable float voltage, but is always higher value--my cheat has been to purchase a cheap lamp timer and plug the battery charger into it... Set the lamp timer to 1 hour per day and monitor the state of the battery charge (hydrometer or accurate DVM).

I do this for vehicles in storage--especially those that have lots of standby loads (Lojack, On-Star, lots of little computers, etc.)... Before, I have tried about three models of (inexpensive) trickle chargers / battery maintainers and they all tried to boil the batteries dry within a few months (don't know if the chargers don't do float, or the small, 180 mA load in one case, was enough to keep the charger from floating).

If these are flooded cell batteries, you should still see a little water loss every month or two--and checking with a hydrometer would be nice.

I don't know about equalization--but it seems like there is no reason to do it very often while "in storage/float"... If the specific gravity starts to vary, equalize. Otherwise once very few-6 months (and just before huricane season)?

If you have AGM batteries, about the same--except maybe lightly equalize once (if your battery instructions tell you too) just before the season begins.

Also, given that batteries are real notorious for failing after a year or three on standby--perhaps you should do a calibrated load test... Take the battery off charger, lest rest for 1 day, and connect a 100 watt light bulb for 5 hours to perform a 20% load test (20% * 105 amp*hour * 12 volts = 504 Watt*hours). Let the battery rest for several hours, measure temperature, voltage, and specific gravity. See that everything points to 80% state of charge... If not (say points to 60% SOC), then it may be time to replace your batteries. If all OK, charge them up and put them on float/standby for the up coming season.

You can also monitor the battery bank voltage as it discharges. When you do this test on new batteries, write down the results (once an hour, or beginning, middle, end) and then compare them with your test the next year. If the voltages start to crash, may also be a sign that the batteries are on their last legs.

-Bill