Is my battery fried?

[dustboy]

I have a Kirkland group 24DC battery. I started storing the trailer indoors, meaning the solar panel wasn't maintaining the battery anymore. When I realized this, the battery was down to about 11.85V and had probably been there for a few weeks.

I parked it in the sun for a few days but the 85w panel wasn't making any progress restoring the battery, so I bought a cheap 1 amp "smart" charger http://www.autozone.com/test-scan-and-specialty-tools/battery-charger/schumacher-1-amp-6-12-volt-on-cord-battery-charger/161797_0_0/. It got the battery back up, but after about 30 hours of charge time it hasn't stopped charging even when the charge voltage is up to 14.6V. I unplugged it, as my solar charger cuts out at 14.2V. The battery holds a charge at about 12.75V but I'm afraid it's going to croak in the middle of a boondocking trip.

[MtnDon]

Take the charged battery to a car parts store and have a load test performed.

Does the battery have removable caps? If so a hydrometer gives a better indication of condition. Let the battery rest for at least 7-8 hours; no loads no charging, before taking sp gr readings. A good battery should show full and all cells within 0.015 of each other. Some batteries are sealed and you can't test the sp gr. Some cells appear to be sealed but actually have caps that are usually ganged in three's. They can be pried off.

An at rest voltage reading of 11.85 indicates the battery is only at about 33% charged. Not at all good if it was for more than a day or three.

How old is the battery? If three years or more it may be wise to replace it anyways.

Re: charging voltages. If that solar charge controller keeps the batteries at 14.2 volts all the time that is also not good. That can cause exc essive water use. Most FLA (flooded lead acid) batteries should be float charged (the long term maintenance charge) at 13.2 to 13.6 volts, depending on temperature. The absorb stage charge is higher, usually in the 14.3 to 14.6 range, again depending on temperature and even battery manufacturer. The better battery chargers take temperature into account; the best chargers have temperature sensors that attach to the battery itself. Those are not common.

[len19070]

I'd like to ad one more thing to Don's statement.

Take your Battery to a place to be tested that doesn't sell Batteries.

Happy Trails

Len

[bdosborn]

Take a driveway camping trip and see how the battery does.

Bruce

[Shadow Catcher]

It was down to about 35% SOC so some damage may have been done, testing is in order. http://www.solar-electric.com/deep-cycle-battery-faq.html

[dustboy]

As usual, all great info. I could get some mileage out of a hydrometer, I have an electric forklift and if you think RV batteries are expensive... yowza!

Out of curiosity, I've been meaning to see how long the dorm fridge in my office could run off my inverter. This might be a good way to test both in one shot!

The A/C charger I bought had a note in the manual that it could kill a deeply discharged marine battery, didn't say how/why. Hope this isn't the case, but the good news is that the Kirkland battery was cheap, and I got a couple years out of it. Glad I didn't kill something more expensive!

I think my solar charger floats at 13.6V.

[Dale M.]

I would be a little cautions with a "cheap" charger, and watch voltages like a hawk.... Today "cheap" usually equates to junk and it may do more harm then good to your battery... I bought a very expensive Odyssey battery for my jeep, and it was only battery I have ever seen that came with a instruction sheet for charging, maintenance and use... And it states do not go over 14.0 volts when charging... Guess I will have to replace my 30+ years old not so great charger if I ever need to do manual charge on Jeeps battery...

All I am saying here is all batteries are different and all chargers are different.... Monitor situation when charging and be aware of battery capabilities/design (capacity) ...

Dale

[dustboy]

Well my little test with the fridge didn't work, my inverter apparently wasn't up to the task. First I blew the 30A fuse going to the inverter, I replaced it with a 40A (I will get a 30A slow blow in there) and the fridge repeatedly tried to start but the inverter couldn't keep up its end of the bargain. Thought for sure a 400w continuous/1000w surge inverter could handle the inrush current. How big an inverter do I need to get that little compressor to turn over?

The battery has been holding steady at 12.8V, I'm starting to think the weak link is my solar and TV charging circuits. The 85w panel in full sun should have been able to make at least 5A, and yet it didn't charge the battery. On the last trip the voltage didn't jump when I started the TV, but the battery's current draw may have been too high and the TV's circuit cut it off.

[MtnDon]

Depending on the individual fridge it is not uncommon to need a 1500 to 2000 watt (rated continuous) inverter to be able to start a refrigerator compressor. The surge capacity is a time limited surge. I've seen peak surge power rated for under 1 second. Not much good for starting a fridge. If that is a modified sine wave inverter that also detracts from the ability to start a fridge as that waveform is less efficient. The fridge motor turns some of the energy into heat; more than with a pure sine wave inverter.


I would expect an 85 watt panel to be able to make 5 amps, at best on a great day.

Re-reading the OP I find it odd that a cheap 1 amp charger worked when the PV did not. Of course the PV system would need about 5 or 6 days to replicate the constant charge from the, 24/7, grid powered battery charger. Do you have the equipment to measure current from the PV to the battery to make sure it is actually working; something like a clamp-on meter is easiest?