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Old 09-17-2018, 11:56 PM   #1
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Best 12v AGM Battery Choice (27 or 31 Group)

Anyone have an opinion on what the best choice is for replacement batteries? I currently have 2 12v batteries (27 series (group)). They are the batteries that came with the RV when we bought it (2016 Sequoia GKS).

We have the residential fridge with the 1000w inverter. Like I said, we currently have 27 series 12v batteries. I understand that 6v gives more AH but right now I am going to stick with 12v.

I really don't know what I currently have. I have never opened the battery box to look at them (I know that is bad... ). I am assuming that they are probably flooded cell batteries. I am definitely thinking about doing AGM so to reduce maintenance.

I have read up on the Magnum charger capabilities and it looks like it can handle an AGM battery. There might actually be a setting that needs to be changed. I believe the default setting is "flooded".

I would like to maybe bump up to the 31 series if possible. I don't know if that size is larger than the 27. Probably depends on the manufacturer.

Anyway, does anyone have an opinion on whether to go with Duracell or Interstate or whatever for a 12v AGM 27 series (or 31 series) battery? These batteries are quite pricey. I am interested to know what you all think.

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Old 09-18-2018, 03:16 AM   #2
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I went with Optima series 24 Bluetop AGM Marine/RV batteries (on sale but still pricey) on my 39MB that had the stock 31 flooded batteries. Bought em at Advance Auto. Replaced the stock “sealed” battery boxes with battery trays & simply installed a larger vent in the battery compartment for increased ventilation. Those stock battery boxes are a terrible design to install, check, or remove heavy batteries in the battery compartment. So far so good. I reset my charger/inverter for AGM charging. Simple to do, search here or online.
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Old 09-18-2018, 05:16 AM   #3
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I've seen some negative reviews of the Interstate AGM's. One of our forum members (Ford Truck Guy) recently converted to Lifeline. I was going to do the same as our two group 31's (Sears Diehard Marine AGM's) are about 5 and a half years old. I took them to the Lifeline distributor in our area. They load tested both and they both were better than new specs. I'd give them a look.

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Old 09-18-2018, 12:26 PM   #4
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Yes Jim, It was me who swapped to Lifeline...

I called Magnum and they and they told me that there is a setting specifically for the AGM’s. AND they also told me that in their eyes, Lifeline was at the top of the list.

They are expensive, but evidently wort the cost, we shall see... There are a lot of folks over on the other forum that I visit that swear by them...

I believe that I paid around $300 each..???
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Old 09-18-2018, 02:21 PM   #5
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Mike to answer part of your question: Yes the OEM batteries are Flooded Cell and if you haven't done anything to them since new, most likely they are dry. I add water twice a year to mine and have never had the plates exposed.
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Old 09-18-2018, 02:40 PM   #6
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Thank you all for the responses. You always have good wisdom to share. Because of the fact that I want to simplify maintenance, I am thinking that I will go with AGM. A couple of questions:

1) When I am storing my coach, I have a campsite that I store it at and I have always left shore power hooked up so to keep the batteries charged all year round. Some people say that you should not charge during storage because of the issue with overcharging and "boiling" the cells (for "flooded" batteries) but I am thinking with the magnum technology, it has those 4 modes of charging and it should not overcharge the battery. Furthermore, AGM batteries don't need water so the "boiling" effect is not an issue. Given that I will go with AGM instead of flooded, what are your thoughts on this? Do you think that the magnum charger will do what it is supposed to do and not overcharge the batteries?

2) I understand that the OEM battery box is a pain but for now, I don't want to change it up. Can I put AGM batteries in there? I was reading that you cannot put AGM batteries in an enclosed space. However, I am thinking that this battery box is vented. Any thoughts?

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Old 09-18-2018, 03:22 PM   #7
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Originally Posted by Mike&Pam View Post

2) I understand that the OEM battery box is a pain but for now, I don't want to change it up. Can I put AGM batteries in there? I was reading that you cannot put AGM batteries in an enclosed space. However, I am thinking that this battery box is vented. Any thoughts?

AGM batteries still give off hydrogen, even though much less than a standard lead acid, so they need to be vented. Your OEM boxes use a natural draft ventilation drawing air in through holes in the bottom and out through that flex hose in the top that leads to the front vent through the exterior wall.

The AGM batteries I got from Sams for RV deep cycle (series 24) were actually shorter than the standard Insterstate battery the Redwood Dealer installed. I don't know about the 27 series. The 31 series are huge, and about 200lbs.
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Old 09-18-2018, 04:30 PM   #8
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I currently have the Exide AGM battery in our FL model, it fits good in the original oem battery boxes. Have had them now 3 years now and I don't have an inverter.
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