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Old 08-04-2020, 03:35 PM   #1
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Join Date: Dec 2018
Location: Breaux Bridge, LA
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Battery question for 2015 Forester 2861DS

We need to change our batteries and I'm having trouble finding the right ones. The current ones are labeled 27MDP which google says is an EXIDE battery. The size does not match, however. Our current batteries (2 found in the step) are 12" wide, 6.5" deep and 8.5"tall. I have researched a ton of recommended batteries but none match. Most of the deep cycle I've found are not as wide. Can I put narrower ones? If anyone has replaced batteries in this model or has any advice please let me know. Thanks, Michelle
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Old 08-04-2020, 03:40 PM   #2
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No answer to your question. But I will be following this thread. I have exactly the same unit. My batteries are also dead.
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Old 08-04-2020, 03:53 PM   #3
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Batteries in my 2861 from Autozone

My new unit came with bad batteries so before my first big trip I got them tested. And both failed. Here is what they put in
Duralast- Marine Starting- 27DP DL.

Seems to have been what was needed.
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Old 08-05-2020, 07:33 PM   #4
2012 Solera
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Our MBS had group 27 batteries in the step:
“Group 27 Batteries: 12.0625 x 6.8125 x 8.875“ (per Google in inches)

I went with Battleborn group 27 equivalents when I recently upgraded.
2012 Solera "S"
Calif SF Bay Area
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Old 08-06-2020, 01:02 PM   #5
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Had to replace the house batteries in our 2016 Solera earlier this year and went with AGM Duracell 27M (12"w x 6.5"d x 7.5"h). Even checked with Progressive Dynamics, the power control center manufacturer, for battery charging compatibility with AGMs, and they said it would be no problem. FWIW, Sam's Club had the best price, $138.88, at the time.
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Old 08-06-2020, 01:19 PM   #6
Join Date: Jul 2016
Location: Bath, NY
Posts: 78
In my 2016 Forester they were 2 type 27 Lead Acid .. when they started not holding charge very well I got 2 BattleBorn LiFePo 100Ah batteries along with a Progressive Dynamics Lithium charger/Converter a Victron Battery monitor and heating pads. Been very pleased with the setup so far. The batteries are guaranteed for 10 years
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Old 08-06-2020, 01:22 PM   #7
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ANY 12V batteries that will fit in the space available are suitable for replacement provided they are Deep Cycle...assuming you boondock...or dual purpose if you don't.
Here are the measurements of the most popular 12V battery sizes. Get the ones that FIT inside your space that have the most amp hours. Sounds like some others are using group 27 so you can check those measurements...but get a group 31 if you can fit them for a bit more time between charging.
10.75x6.75x9.38 75a/h G24
12.5x6.76x9.38 95a/h G27
13x6.75x9,5 105 a/h G31
2015 Georgetown 280DS
2019 Vespa Primavera 150's (pair)
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Old 08-06-2020, 01:34 PM   #8
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Check the dimensions. We have battery boxes that hold our existing group 27 batteries. I measured the box to see if I could fit some group 31 batteries into them. I measured the boxes and they are too short. But in looking at new group 27 batteries I discovered that there is no standard size. The various group 27 batteries are similar but they do vary in size. I found at least a couple of group 27 batteries that would not fit into our existing group 27 boxes.
2015 cardinal model 3825fl
2015 dodge ram 3500 dually
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Old 08-06-2020, 04:07 PM   #9
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I replaced my 2016 forester 2801 group 27 batteries with two Duracell deep cycle group 31 AGM batteries. Fit perfectly.
2016 Forester GTS 2801QSF
2011 Jeep JK Toad
Habitual RV Modifier
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Old 08-06-2020, 04:41 PM   #10
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Location: South Carolina
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I installed new batteries on our 2011 Sunseeker model 3100 this morning. I put in Duracell BCI size 31 batteries. They fit fine. There was one problem. The hold down strap's clamp is on the side, between the battery and the battery box sidewall. It was hard to reach with the original size 27's, and impossible with the size 31's. I had a webbing belt in my stash that was just like the hold down strap. I put one end through the hold down strap clamp and put the buckle on top of the batteries where it's accessible.

The Interstate size 27's that I removed, which weren't the original ones, and all the other size 27's I looked at, have lifting straps that go through lugs on the ends of the battery cases. The Duracell size 31's have a built-in lifting handle, and don't have the lugs on the end. (The original batteries had built-in lifting handles.) Although the charts for BCI battery sizes give the 31 as 0.9 inches longer than the 27, without the lifting strap lugs, there's not much difference. The lugs are not included in the BCI case dimensions.

Whatever you buy, be sure you get true deep cycle batteries, not starting batteries. Some, like Duracell, Interstate and NAPA, have both threaded stud terminals and standard posts so they can be used as a starting battery. Battery vendors have BCI size 31 starting service batteries that give high amps for short periods and are great for trucks, but are not what you need for an RV that uses low amps for long periods.

I don't know if the Duracell brand is any better or worse than other brands that are readily available, but the price was good at Batteries Plus. If you read the many posts about batteries, it seems that Trojan brand is highly recommended, but the prices I found are double what I paid. For our use, it's not worth the difference. As with conventional flooded lead acid versus AGM versus lithium, no battery is best for everyone.
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2011 Sunseeker 3100
2016 Ford Edge Toad
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