Load testing house batteries

[Unicorn Driver]

Hi there,

I would like to load test my house batteries while monitoring them with a Trimetric.

My batteries are two 232mh 6 volt.

From looking at the Go power usage calculator I would use 22amp an hour running the furnace, stereo, fridge, lp detector and all coach lights (all Led except bay bulbs).

Correct me if I am wrong, but at 22amp that would mean I would use roughly 10% battery every hour.

If I monitored for 5 hours would this be a good load test? Or am better doing a lighter load over a longer time.

Thanks,

Stephen

[twinboat]

The 20 hour rating works out to 5 amp draw, per 100 AH.( 5 amps X 20 hours ).

Having 232 AH, you should test them at about a 12 amps draw.

You should be able to run that load for a bit over 9 hours and then get a 12.06 voltage reading after a few hours rest.

Make sure you have charged them to 100% capacity before testing.

If you double the amp draw, you will need to use the 10 hour rate. At that rate you will have a bit less capacity. The battery specs should list them.

[Unicorn Driver]

Originally Posted by twinboat

The 20 hour rating works out to 5 amp draw, per 100 AH.( 5 amps X 20 hours ).

Having 232 AH, you should test them at about a 12 amps draw.

You should be able to run that load for a bit over 9 hours and then get a 12.06 voltage reading after a few hours rest.

Make sure you have charged them to 100% capacity before testing.

Great, I will do a 12amp draw so.

I have has the generator running for about 5 hours this week so battery should be fully charged, will check before hand though.

[vsheetz]

Buy or borrow a load test box. Or go to most auto parts store and they will load test for you. If the batteries are weak or bad it will be evident.

[ka5gyo]

Hi Twinboat.
How would you test 8- 6 volt batteries (232 amp hr)each in series/parallel..
4 - banks 12 volts
load / time ?

[twinboat]

Originally Posted by vsheetz

Buy or borrow a load test box. Or go to most auto parts store and they will load test for you. If the batteries are weak or bad it will be evident.

Most load testers are checking cranking amps not AH capacity.

[Unicorn Driver]

Originally Posted by twinboat

Most load testers are checking cranking amps not AH capacity.

It ia indeed the AH I am looking to test.

[Searching_Ut]

Originally Posted by twinboat

The 20 hour rating works out to 5 amp draw, per 100 AH.( 5 amps X 20 hours ).

Having 232 AH, you should test them at about a 12 amps draw.

You should be able to run that load for a bit over 9 hours and then get a 12.06 voltage reading after a few hours rest.

Make sure you have charged them to 100% capacity before testing.

If you double the amp draw, you will need to use the 10 hour rate. At that rate you will have a bit less capacity. The battery specs should list them.

This is probably the best procedure being as how an actual cap check based on manufactures specs would require you to draw the batteries down to 10.5vdc which isn't good for them long term. Keep in mind when trying to compare against manufactures spec that temperature also comes in to play. Trojan for instance specs their performance at 80 degrees for testing. You'll have less capacity at lower temperatures.

Once you get used to how your batteries behave under load and different levels of discharge based on your trimetric readout, it will get easy to tell with a good educated guess much life they have left without having to actually do a formal capacity test of any sort.

[Unicorn Driver]

Originally Posted by Searching_Ut

This is probably the best procedure being as how an actual cap check based on manufactures specs would require you to draw the batteries down to 10.5vdc which isn't good for them long term. Keep in mind when trying to compare against manufactures spec that temperature also comes in to play. Trojan for instance specs their performance at 80 degrees for testing. You'll have less capacity at lower temperatures.

Once you get used to how your batteries behave under load and different levels of discharge based on your trimetric readout, it will get easy to tell with a good educated guess much life they have left without having to actually do a formal capacity test of any sort.

Thanks,

I am trying to figure out what condition my batteries are in :-)

[twinboat]

Originally Posted by ka5gyo

Hi Twinboat.
How would you test 8- 6 volt batteries (232 amp hr)each in series/parallel..
4 - banks 12 volts
load / time ?

47 amps until 12.06 resting volts on a 928 AH bank.

New batteries should last about 10 hours at that draw before dropping to 50% capacity.

If there all the same age, you can do 1 set at the lower draw.

There are other ways to test deep cycle batteries using high amp battery load testers, hydrometers and digital volt meters, Google will lead you to them.

[vsheetz]

Originally Posted by twinboat

Most load testers are checking cranking amps not AH capacity.

Yes, I understand. In rereading the OP goals I see he's not having a battery problem per se, as I originally thought - instead looking to evaluate the capacity status. Please disregard my comment. Thanks.

[Unicorn Driver]

Originally Posted by vsheetz

Yes, I understand. In rereading the OP goals I see he's not having a battery problem per se, as I originally thought - instead looking to evaluate the capacity status. Please disregard my comment. Thanks.

You are both right.

My batteries may be compromised due to neglect of watering, I am trying to figure out what condition they are in (and evaluate capacity).

[powercat_ras]

If you have an DC-AC inverter tied to your batteries you can use an AC load to create DC load to do your load test without buying a DC load box.

[Unicorn Driver]

Originally Posted by powercat_ras

If you have an DC-AC inverter tied to your batteries you can use an AC load to create DC load to do your load test without buying a DC load box.

I do have an inverter bit only a 400w one, I could run a 32inch lcd tv and blue ray but not much else.