field testing a battery banks "health"

[pjstock]

applying testing tools to my (probably 18 year oldtor ) GEL batteries I am getting:

1) from a load tester... a reading I cannot decipher
2) from a more fancy battery tester, on various battery type settings, generally a REPLACE or POOR reading

but can I field test this battery?

for instance, at 230pm this afternoon it was reading 13.02V
I have since run the 12v 42W refrigerator for... 6 hours and the auxiliary battery voltage has dropped to 12.44v
so down 0.56v

so, based on that, can I calculate the health of my GEL batteries?

 

[45North]

18 years! Just replace it.

 

[SunDave]

Hard to tell with a fridge since it can cycle on and off, but you have the right idea for a real world test of a slow draw. Especially if you find a more consistent load. A slow draw test like that won't be the same as trying to start a motor though.

 

[pjstock]

18 years! Just replace it.

that is the plan. which is in process.
I was just curious.

 

[45North]

Sounds like a plan, eh

 

[seneysolar]

In general, multiple batteries that make up a "bank" should be separated for testing as individual batteries.
They need to be charged to full while monitoring temp, let rest for a few hours and then discharged at a constant rate, usually associated with the rated capacity "c" rate.

As mentioned above, 18 year old batteries are not worth the time to do it