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View Poll Results: Should I replace my 2 starting batteries just because they are almost 7 years old?
should I replace the batteries? 4 50.00%
how can I test the batteries? 4 50.00%
Voters: 8. You may not vote on this poll

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Old 01-21-2022, 07:10 PM   #1
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Exclamation Battery testing

My Class A has two 12 volt starting batteries, group 31. They'll be 7 years old in May, but have been working fine; never had to use the jump start feature. Is it time to replace them just because of their age, or is there some way to test them to see if they're still strong. They are hooked up to a Battery Minder when not on the road, which is most of the time. Is there any way to test them without removing them from the RV? Would appreciate some help from those in the know. Thanks.
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Old 01-21-2022, 07:46 PM   #2
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You could take them to an auto parts store or battery shop and have them load tested. Most people will use a battery until they won't start a vehicle any longer. Personally, I wouldn't use a battery over seven years. Group 31 starting batteries are relatively cheap and are a maintenance item just like oil and tires.
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Old 01-21-2022, 08:05 PM   #3
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I'm going to replace mine this spring at 8yrs old.

Also never needed to use the boost switch.
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Old 01-21-2022, 08:17 PM   #4
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7 yrs......you got your monies worth out of those Group 31's

Time to replace.
*Or you can wait until they fail
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Old 01-21-2022, 08:32 PM   #5
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If you wanted, you could do what is called a cranking voltage test. Fairly simple and it does work and will let you know how well the batteries are holding their charge. I taught this easy little test to all my student.

It's using the starter motor to simulate a significant ranking load not unlike what the standard load testing machines will do.

Hook a battery tester across the cranking batteries. That will give you the static charge on the batteries. I'm assuming they are hooked up parallel, so you have 12 volts and the cranking current tied together. You should read about 12.6 static volts or slightly more. Disable the engine so it won't start just crank. You could pull the fuel pump relay or disable the ignition system. You do not want the engine to start just crank.

Once that is set up crank the engine for 15 seconds while monitoring the voltage at the batteries. You are loading down the batteries using the cranking motor and engine compression as the electrical current load. The voltage should stay above 10.9 volts until the end of 15 seconds.

If it falls below 10.9 V the batteries can't hold a proper charge when loaded down. If voltage stays above 10.9 V your batteries are capable of providing the current and voltage to do its job.
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Old 01-21-2022, 08:37 PM   #6
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If you wanted, you could do what is called a cranking voltage test. Fairly simple and it does work and will let you know how well the batteries are holding their charge. I taught this easy little test to all my student.

It's using the starter motor to simulate a significant ranking load not unlike what the load testing machines will do.

Hook a battery tester across the cranking batteries. That will give you the static charge on the batteries. I'm assuming they are hooked up parallel, so you have 12 volts and the cranking current tied together. Disable the engine so it won't start but will crank. You could pull the fuel pump relay or disable the ignition system. You do not want the engine to start just crank.

Once that is set up crank the engine for 15 seconds while monitoring the voltage at the batteries. You are loading the batteries using the cranking motor. The voltage should stay above 10.9 volts until the end of 15 seconds.

If it falls below 10.9 V the batteries can't hold a proper charge when loaded down. If voltage stays above 10.9 V your batteries are capable of providing the current and voltage to do its job.

Turn headlights on for 15 minutes prior...leave on when cranking
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Old 01-21-2022, 08:41 PM   #7
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I always wait until I need to boost the starting battery before replacing it.
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Old 01-21-2022, 11:01 PM   #8
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My chassis battery lasted 10yrs after coach battery replaced at 7yrs.
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Old 01-22-2022, 06:23 AM   #9
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My AGM starting and house batteries are 14 yrs old and still working great.

I would not replace them till they show signs of failing ( slow engine cranking). Some batteries just last a lot longer. I had new batteries fail anywhere from 1 to 4 yrs.
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Old 01-22-2022, 07:26 AM   #10
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Quote:
Originally Posted by rvcaptain View Post
My Class A has two 12 volt starting batteries, group 31. They'll be 7 years old in May, but have been working fine; never had to use the jump start feature. Is it time to replace them just because of their age, or is there some way to test them to see if they're still strong. They are hooked up to a Battery Minder when not on the road, which is most of the time. Is there any way to test them without removing them from the RV? Would appreciate some help from those in the know. Thanks.


I donít replace mine just because.
When you do take pictures and mark all wires.
Replacing batteries is the most self inflicted screw up.
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Old 01-22-2022, 09:02 AM   #11
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Thank you all for your responses, particularly TeJay's specifics on how to test and Old Biscuit's comment. I'm glad to see there is battery life after 7 years. Temperature has been in the teens or single digits here in NJ the last few days. I'll try to start the RV tomorrow morning while its still cold, then will test the batteries next week. Thanks for your help.
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Old 01-22-2022, 11:24 AM   #12
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Old - Biscuit,

Not a bad idea. I never thought of doing that. That might be more appropriate in the spring, summer and fall. Adding head lights will definitely add more current demand but, in the OP's case it may not be necessary. He's reporting the daily temps to be in the teens and lower. That's more than enough added lowered battery efficiency to test the batteries.

At those temps you can lose 20% to 40% battery efficiency. There are charts out there telling you how much efficiency is lost as temps drop.
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Old 01-22-2022, 11:30 AM   #13
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Headlights on for 15 minutes places a demand on batteries...then cranking completes the easy at home load testing
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Old 01-22-2022, 01:37 PM   #14
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Quote:
Originally Posted by chuckftboy View Post
You could take them to an auto parts store or battery shop and have them load tested. Most people will use a battery until they won't start a vehicle any longer. Personally, I wouldn't use a battery over seven years. Group 31 starting batteries are relatively cheap and are a maintenance item just like oil and tires.
I agree, well put.
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