Deep cell batteries

Does a standard load test on a deep cycle battery tell you anything? I think that several of my fence charger batteries have gone south on me but only the smart charger is showing a fault at this point (other than they won't take a charge well). I have a load tester there but thought it was probably a moot point since they don't have many CCA's. They are only a couple of years old (Interstate) and haven't been run all of the way dead. They don't have an easy life out in the fence row, though.

Yes. If it is not over done, a modest (100 amp) load can tell rapidly if a deep cycle battery has a chance of operating. If voltage drops off to less than 10 at 100 I would be suspect. Best bet is to charge it fully at 10 to 15 amps tapering to 5 of so for 3 hours, then a one amp trickle. if left for 3 days it should show good performance if not, it might be warranty time. Jim

I gave my 100a load tester to my BIL. He uses it on his golf cart batteries. I bought a battery conductive tester. I feel it the way to go. That's what most places that sell batteires use. It will give you the CCA on deep cell batteries all the way to small motor cycle batteries.

You can even see what a change in temp does to the CCA.

Yes, but not much. A deep cycle battery will load-test around 80% of what a standard cranking battery will of the same voltage and weight assuming they are both 12 volt batteries. That is you are using a real load-tester with a carbon pile and not some electronic "simulated" load-tester. CCA isn't much of a useful figure anyway since it allows the test down as low as 7.2 volts. 7.2 volts isn't of much use turning a 12 volt starter since it needs 9 volts.

Batteries meant for cranking are rated by RC (reserve capacity) to tell you "how much power for how long." Deep cycle batteries use AH (amp hours). You can use math to change one figure to the other.

Yes indeed, a Load Test in which you place a relatively heavy load on a battery and then observe the voltage over a time period gives an indication (I'm NOT saying it tells everything or is perfect, but it does provide an "indication") as to the condition of a battery. If you measure each cells specific gravity and combine that with load testing and voltage measurements you have at least some idea of the batteries condition.

I agree with Professor Jim, I would give it a good charge and check electrolyte levels then do a load test n see what happens.

The life of the battery depends a lot on how well its kept charged and the charge characteristics (such as if a smart 4 stage charger was used) and how many times and to what depth of discharge its been subjected to.

Charge it, load test it, check specific gravity and levels n see what happens.

John T

I load test my deep cycle battery. I have the carbon pile tester so can put as many amp load on as I want. That will tell you a lot about a battery but it will not tell you how long it will continue to deliver a small rate of discharge. We used to find out these things out in the fish house on the lake. Hook the lights to the battery and see how long before you were in the dark. Amazing how different batteries would perform. Onto a little different situation here, but, I have a two year old battery in the riding lawn mower. It started giving problems late this fall. Would not crank engine. Jump it, check charging rate, voltage normal over 14 volts but next day,same thing. Took battery out , brought it home to check it. After sitting for a few days, the open circuit voltage was 12.4. Put my little test light on it and voltage dropped to 10 volts. Could not even operate a small test light with out voltage dropping to 10. So, I left the test light on to run it down. Two days later, test light still burning, voltage down to maybe 6 or 8 volts, can't remember. Put a larger lamp across terminals and ran it stone dead. Read almost no voltage after removing lamp. Left it sit a day, voltage reads like dead battery should, just below 12 volts. Hooked it to slow, 6 amp charger, it charged at about 4 amps until reached over 14 volts. Removed charger, hooked lamp back on , run it dead again and recharge. Left it set couple days, 12.6 volts open circuit voltage. Put load tester on over 150 amps and it held it over 10.5 volts for 15 seconds. Recharged to make up for load removal. Letting it set to see what happens.