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Old 05-13-2019, 09:37 AM   #1
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Is my Battery Going Bad?

I purchased the van in April, 2019. It has 2 deep cycle SRM-27 Interstate wet cell house batteries purchased April 2017. I checked the electrolyte on both batteries and they are full. I recently purchased and installed an AIMS 600W pure sine wave inverter-charger with remote panel which shows battery voltage, input/output, etc. Prior to installation of the AIMS, I didn't know the charge level of the battery, as if that would be an issue.

I have had the House system hooked up to a 15A garage outlet for about a week. The battery status on the remote panel shows the batteries to be at 12.6V. When I check the voltage of each individual battery (although they are still connected), my voltmeter reads 12.12V.

Putting the discrepancy aside for a moment, I can't seem to get a higher charge. Are my batteries dying? Any insights?

Frankly, I have no problem riding it out and buying a sealed system when they die.

Thanks! Terry
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Old 05-13-2019, 01:49 PM   #2
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I have had the House system hooked up to a 15A garage outlet for about a week. The battery status on the remote panel shows the batteries to be at 12.6V. When I check the voltage of each individual battery (although they are still connected), my voltmeter reads 12.12V.

...assuming that you are checking the battery voltage with the van disconnected from your 15A garage outlet after an hour or so of letting the batteries settle out....


In very rough terms, fully charged is around 12.8V and 50% state of charge is around 12.2V.....12.6V has some life left, 12.12V not so much.....

"One test is worth 1000 expert opinions".....so..

Run your inverter with a reasonable load (like 500W) and see how long it takes to get down to 12V......
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Old 05-13-2019, 01:53 PM   #3
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Could be bad battery, but could be a parasitic drain. Do what Boywonder recommends, but beyond that the best way to check the health of your battery is a load test by a auto shop / battery shop you trust (remember that they want to sell you a new battery).




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Old 05-13-2019, 02:44 PM   #4
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...assuming that you are checking the battery voltage with the van disconnected from your 15A garage outlet after an hour or so of letting the batteries settle out....


In very rough terms, fully charged is around 12.8V and 50% state of charge is around 12.2V.....12.6V has some life left, 12.12V not so much.....

"One test is worth 1000 expert opinions".....so..

Run your inverter with a reasonable load (like 500W) and see how long it takes to get down to 12V......
I was not checking with the battery disconnected, but I've now disconnected it and will check, again, in an hour. Then, I'll run a 350W load on it (the closest I can come up with) and see how it does.

BroncoHauler - Yes, I will probably need to go to a dealer. I'd prefer an AGM battery, anyway. I'm not wild about the wet cell.

I'm driving to the Wisconsin Driftless area Thursday to do some Trout fishing, so I can check it after that 4 hour drive, too.

Thank you! Terry
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Old 05-13-2019, 03:11 PM   #5
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I was not checking with the battery disconnected, but I've now disconnected it and will check, again, in an hour. Then, I'll run a 350W load on it (the closest I can come up with) and see how it does.

So you saw 12.6V with the shore power charger plugged in?? ..Now you have me questioning your voltmeter....seems like all of your readings are low.


What does your voltmeter display if you check the starting battery under the hood with the engine running? It should be around 14V with the engine revving a little.
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Old 05-13-2019, 03:12 PM   #6
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I unhooked from the garage 15A plug. After about 30 minutes, the house battery was at 12.3V as indicated by the remote panel (from 12.6V). I then turned on an interior LED light plus the 2.4A refrigerator and it immediately dropped to 12.1V on the remote panel. Using my voltmeter, I checked the voltage of one of the batteries at 12.09V.

I'll go to my local RV dealer, or maybe Batteries+Bulbs, and get a load test.

Thanks, again. Terry
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Old 05-13-2019, 03:21 PM   #7
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First assuming that you were not actively charging the battery. I would have to say that you need to check the accuracy of your multi-meter and/or your inverter/charger. It would not make sense that your remote for inverter/charger would read 12.6 V and that your meter at the battery would be 12.16 V. If anything it should be the other way around and even then the difference would be to high. You should see some drop based on the voltage drop of wiring at the terminals of inverter/charger. I would measure the terminals at the inverter/charger with the meter and compare.

Meters will drift overtime, and that can even be worse with cheaper ones. When I was in charge of test engineering labs, we calibrated all the test equipment every year.

You should verify the voltage of your charger also, float level would be 13.3 and boost or absorption around 14.8 for that charger. If you were actively in float mode you should read 13.3 on the remote panel, you may have some drop at the battery, but I would not expect anything less than 13.2.


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Old 05-13-2019, 03:56 PM   #8
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With my engine running at idle, I checked the chassis battery with my digital Radio Shack multimeter and got 14.4V.

With the engine still running at idle, I checked the voltage readout of the house battery at the remote panel and it showed 14.2V. I did not check the voltage at the house battery terminals.

Based on Scalf77's comment about voltage drop, the 0.2V difference makes sense. But, I was pretty surprised the house battery voltage was running so close to the chassis battery voltage.

Thank you. Terry
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Old 05-13-2019, 04:07 PM   #9
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fwiw, interstate is awesome with battery replacements whether your the original purchaser or not, but iirc, their batteries are only warrantied for 2 years, but they will prorate.
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Old 05-13-2019, 04:17 PM   #10
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fwiw, interstate is awesome with battery replacements whether your the original purchaser or not, but iirc, their batteries are only warrantied for 2 years, but they will prorate.
Thanks, Shenrie. Who is iirc? Also, I want to know how these batteries went kaput. The PO struggled with the batteries, but I don't know if that was due to poor management/maintenance of the batteries or something in the house electrical system. I'd hate to replace them and find out they're bad in 2 years.

Thank you. Terry
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