What is simple test of battery power?

[mickjetblue]

I have 4 deep cycle batteries in the garage. They are all "good batterries", in that none of
them have failed to recharge. They range in age from 2 to maybe 5 years old. I have sort
of rotated them around.

Now, I am wondering how I can tell which battery is best, and which battery is most
likely to fail. Since they all reading 12v, and all will take a charge, is there a simple test,
short of putting them one at a time to a trolling motor, to tell how "good" each battery
really is?

 

[mthieme]

Re: What is simple test of battery power?

Specific gravity using hydrometer and a load tester.
You're local battery store or Autozone will do a load test for free.

 

[Silvertip]

Re: What is simple test of battery power?

Just because the battery voltage measures 12.6 or thereabouts does not mean it is a good battery. As mentioned, a load test by a local auto store will tell you which batteries are good and which are toast.

 

[mickjetblue]

Re: What is simple test of battery power?

Thanks for the advice. I found and ordered a load tester, and I'll check them out.

I'll also start bringing a portable jump starter on board the boat, just in case.

 

[mickjetblue]

Re: What is simple test of battery power?

Update - the battery load tester arrived today, so I put them to the test.
I had charged each of them just last week, and knew they were up on water.

The load tester is a 2 stage test, with the first part being a voltage check when
you connect the clamps to the battery. The second part is holding on the toggle
switch for 5 to 10 seconds and reading the voltage on the test meter during that time.
The simulated load appears to be a heater element working as a load on the battery.

Anyway, 2 of the batteries read 13 volts at start, and read good under load.

1 battery read about 12.8 volts, and read weak under load.

1 battery read about 12.8 volts, and read almost as weak as the other weakest one.

Now I know which one is the weakest, and needs to go. Another is marginal.
Definitely worth the test.

 

[dan t.]

Re: What is simple test of battery power?

those cheepo load testers lie, get it tested with a proper carbon pile tester