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Old 01-12-2022, 04:46 PM   #1
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Need to replace both 12v chassis batteries - what size are these?

Both my chassis batteries are bad. They got discharged and they won't take a charge anymore. When I bought the RV, the previous owner had just replaced the chassis batteries with these, and from what I'm told they're really low quality batteries. They're date coded October, 2019. I'm thinking they should have lasted longer than this, but again they're really low quality batteries.

My problem is they're not labeled with a size. I've asked Newmar via email since they never answered the phone and I haven't heard back from them. Does anyone with this era Newmar DP know what size batteries are in there? Or, can anyone tell by looking at these what size they are?

Is there any reason to go with AGM? The 6v house batteries in there are wet cell, so there's no keeping the battery compartment cleaner benefit to going AGM in that respect. Other than keeping the battery compartment cleaner, is there an operational benefit to AGM's?

I'm thinking by appearance they seem to be this size:

Is size 31 common in this application?
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Old 01-12-2022, 07:03 PM   #2
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They are 31's. Buy interstate or Deka brands.
No benefit to AGM there.
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Old 01-12-2022, 07:14 PM   #3
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Old 01-12-2022, 07:14 PM   #4
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An additional thought, make sure that these chassis batts get charged when on shore power. Some manufacturers did not set this up. If not then either buy it a separate mini charger to keep them up or simply use a jumper cable from output positive terminal between the output of both chassis and house banks when not driving.
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Old 01-18-2022, 02:30 PM   #5
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Agree - not much reason to buy AGM chassis batteries. For cranking a diesel, you generally want a pair of batteries rated at around 1000 CCA each, and that usually means the Group 31 case size. They should last 5-7 years in normal use.

If you are a Sam's Club or Costco member, they usually have a good price on Group 31 cranking batteries. Freightliner dealers too - their Alliance brand batteries are reliable and usually reasonably priced.
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Old 01-18-2022, 03:13 PM   #6
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Look like group 27 to me.? Less than 2 1/2 years old they shouldn't need be replaced unless abused.
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Old 01-18-2022, 03:27 PM   #7
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You can measure to be sure.
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batteries, chassis, chassis batteries, replace, ace, 12v

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