Interstate SRM-24 Battery Replacement?

[DeanAir]

I have a 2014 23FB, and it has two Interstate SRM-24 batteries. It is a pain in my area to purchase exact replacements. Can anyone recommend replacement batteries, that are exactly the same physical size?

[Bill M.]

I think any group 24 battery will be the same size. Look at the battery and get ones with the same style posts or connections. And look to see if you want flooded cell or AGM. Interstate is just another brand of battery. Nothing magical about them.

[AirMiles]

Your batteries are a very common 12 Volt Group Size 24DC Deep Cycle battery that can be bought at any Walmart or discount auto parts store such as AutoZone or Advance Auto Parts. Sam's Club and Costco are also great places to buy these batteries. Just make sure the batteries say "Deep Cycle" or "Marine/RV" and are not "Starting Batteries". And as the previous poster stated, buy them with the same dual post setup as your current battery so you don't need to change the battery cables. I purchased some at Walmart to help out a fellow Airstream owner on the road from Walmart that had the exact same dual posts as the Interstates you are replacing. https://www.walmart.com/ip/EverStart...24DC/180350522

[uncle_bob]

Hi

If you are out shopping for batteries, most AS trailers will accept a group 27 battery as well as a group 24. The group 27 is a bit larger and has more capacity. Battery prices can be a bit weird. Sometimes you can find group 27's at the same price (or less ... what? ...) as a group 24. As mentioned above, you want the deep cycle versions. '

With lead acid batteries, weight is good. They should be heavy. One way to compare different brands is to simply look at the weight of the battery. It's not a prefect thing, but it will give you some idea what is what.

Bob

[mpsgolf]

Group 24s are roughly the same size. I found minor variations in group 27 when I was shopping but there should be room in your batt box to deal with this.

You want a true deep cycle battery spec’d in Amp hours (Ah). Not a starter battery spec’d in CCA. Deep cycles have thicker lead plates and are able to be charged and discharged within limits.

[DeanAir]

Originally Posted by mpsgolf

Group 24s are roughly the same size. I found minor variations in group 27 when I was shopping but there should be room in your batt box to deal with this.

You want a true deep cycle battery spec’d in Amp hours (Ah). Not a starter battery spec’d in CCA. Deep cycles have thicker lead plates and are able to be charged and discharged within limits.

Thanks for all of the responses. This is a great forum.

[rustyoldman]

Don't guess....measure your battery boxes....group 24 batteries are 10.3 inches long and group 27 batteries are 12.1 inches....if you can fit the group 27 batteries in your boxes, but the larger ones. If your boxes are too small for 27's, you should consider new boxes able to hold the 27's and possibly the 29 series batteries. Only disadvantage to going big is cost and weight. Personally I have started with 24's on three trailers because that is what the dealer installs because they are cheaper...on all three trailers I moved up to 27's an one up to 29's
Compare batteries by amp hours....very important.

[JamuJoe]

Originally Posted by DeanAir

I have a 2014 23FB, and it has two Interstate SRM-24 batteries. It is a pain in my area to purchase exact replacements. Can anyone recommend replacement batteries, that are exactly the same physical size?

You should MEASURE, as there are build variations in these trailers.
I recently moved up to GP27 AGMs (Lifeline) in our 2011 FC23FB for greater capacity. I had to remove that center hold-down (not needed), bend down the lip to which the battery compartment lid was attached and reverse and reattach the lid. A 30 min job with pliers and drill.

[Ronman]

Not sure where you are but we have an Airstream guy who does box extensions thus allowing for 6 volt batteries. Much better functionality.

[pteck]

Group 24's of any brand will drop right in.

I echo those who have already encouraged you to measure if you are going to try to fit group 27s. Not all stock AS boxes are going to readily fit this size without some minor modifications. They might be just wide enough that you'll need to grind part of the lip (usually ~3/8" under the hinge end of the lid) to actually put these batteries in.

Next size up, would be 6V golf cart type batts. These would be really worth your while, even skipping the group 27s, as they are true deep cycle batts. Firstly, they outright have more capacity. If you cycle them like a typical 12V to 50%, they'll have a 2.5 times advantage in cycle life. Secondly, they are truly deep cycle, in that you can regularly go to 80% cycling (~11.7V), and still easily achieve the cycle life of a 12V battery cycled to 50%. Meaning ~180Ah usable. In term of modifications to your trailer, usually requires a lid extension (as they are taller), that is readily available from venders.

[uncle_bob]

Hi

Keep in mind that if you do go to the golf cart batteries (Trojan T-105's for example), you will need to replace your converter / charger with something custom to get a full charge into them. Without the custom charger, the amp hours out of them will actually be *less* than you would get with group 27's.

Bob

[JamuJoe]

Originally Posted by pteck

Group 24's of any brand will drop right in.

I echo those who have already encouraged you to measure if you are going to try to fit group 27s. Not all stock AS boxes are going to readily fit this size without some minor modifications. They might be just wide enough that you'll need to grind part of the lip (usually ~3/8" under the hinge end of the lid) to actually put these batteries in.

Next size up, would be 6V golf cart type batts. These would be really worth your while, even skipping the group 27s, as they are true deep cycle batts. Firstly, they outright have more capacity. If you cycle them like a typical 12V to 50%, they'll have a 2.5 times advantage in cycle life. Secondly, they are truly deep cycle, in that you can regularly go to 80% cycling (~11.7V), and still easily achieve the cycle life of a 12V battery cycled to 50%. Meaning ~180Ah usable. In term of modifications to your trailer, usually requires a lid extension (as they are taller), that is readily available from venders.

Actually, Lifeline GPL-27T AGM's are true deep cycle.
A pair will cost $740, weigh 124# and provide 200 AH.
Compare to two Lifeline GPL-4CT (golf cart) AGM's at $800, 132# and 220 AH.

Going from GP24 to GP27 is a big jump in AH (160 to 200) for reasonable cost and weight increase. DIY mods to the battery box cost nothing.

The 4CT's are good value, before the cost of modifying the battery box.

$/AH comes down even further with GPL-6CT's, but the weight (180#) becomes a factor in addition to even greater height.

I have Lifeline GPL-27T's in our Airstream and GPL-4CT's (three pair) in our sailboat.

I would never intentionally cycle my AGM's to 11.7v. 80% DOD will bring the expected life down to 500 cycles.

[pteck]

Originally Posted by JamuJoe

Actually, Lifeline GPL-27T AGM's are true deep cycle.
A pair will cost $740, weigh 124# and provide 200 AH.
Compare to two Lifeline GPL-4CT (golf cart) AGM's at $800, 132# and 220 AH.

Going from GP24 to GP27 is a big jump in AH (160 to 200) for reasonable cost and weight increase. DIY mods to the battery box cost nothing.

The 4CT's are good value, before the cost of modifying the battery box.

$/AH comes down even further with GPL-6CT's, but the weight (180#) becomes a factor in addition to even greater height.

I have Lifeline GPL-27T's in our Airstream and GPL-4CT's (three pair) in our sailboat.

I would never intentionally cycle my AGM's to 11.7v. 80% DOD will bring the expected life down to 500 cycles.

Good comparison and data for these Lifeline AGMs. I'd agree with you if the comparison was focused on these, more specialized (and $$$) batteries. I can replace my flooded's almost 4x over, and have more usable capacity as I don't care if they fail in say 3-4 yrs.

My input was in regards to classic flooded batts. There's really no such thing as a flooded deep cycle 12V standard case battery, at least compared to the 6V flooded deep cycle.

My point is that you'll get 2.5X the cycle life out of the 6V flooded battery, vs a 12V flooded battery.

Capacity is an elastic parameter that is always traded with battery longevity.

50% is not a magic depth of discharge parameter. If a battery has 2.5X better cycle life, discharging it down to 80% can result in potentially still battery longevity versus a typical 12V.



All you wanted to learn and more here on why you want 6V batts:
https://marinehowto.com/what-is-a-deep-cycle-battery/

[Vantair]

A vast improvement with the 6v Golf batts and AGM but it is tricky finding a workable size for earlier than 2017 battery boxes.

Having a 2005 and smaller battery box fashioned slight lip “removal” (not height extension) allows a nice snug fit of the Fullriver 6V AGMs 220ah each.

Randy at Best Converter has em

[JamuJoe]

Originally Posted by pteck

Good comparison and data for these Lifeline AGMs. I'd agree with you if the comparison was focused on these, more specialized (and $$$) batteries. I can replace my flooded's almost 4x over, and have more usable capacity as I don't care if they fail in say 3-4 yrs.



My input was in regards to classic flooded batts. There's really no such thing as a flooded deep cycle 12V standard case battery, at least compared to the 6V flooded deep cycle.



My point is that you'll get 2.5X the cycle life out of the 6V flooded battery, vs a 12V flooded battery.



Capacity is an elastic parameter that is always traded with battery longevity.



50% is not a magic depth of discharge parameter. If a battery has 2.5X better cycle life, discharging it down to 80% can result in potentially still battery longevity versus a typical 12V.



Attachment 324878



All you wanted to learn and more here on why you want 6V batts:

https://marinehowto.com/what-is-a-deep-cycle-battery/

Ahh, we all tend to make comments from our own perspective. I abandoned flooded lead acid batteries years ago in favor of AGM's. With my yacht in storage for 6 mos per year, and the Airstream sometimes stored for 3 mos, AGM's became my clear choice for lower self discharge rates, faster recharge, increased life, and lesser requirements for maintenance. I'd also prefer to put fewer batteries in the landfill. Yet, flooded lead acid batteries are more economical for those who can attend to them properly. Battery technology and economics are evolving rapidly, so it is worthwhile to be informed and open to options.

Good discussion!

[JamuJoe]

Originally Posted by JamuJoe

Ahh, we all tend to make comments from our own perspective. I abandoned flooded lead acid batteries years ago in favor of AGM's. With my yacht in storage for 6 mos per year, and the Airstream sometimes stored for 3 mos, AGM's became my clear choice for lower self discharge rates, faster recharge, increased life, and lesser requirements for maintenance. I'd also prefer to put fewer batteries in the landfill. Yet, flooded lead acid batteries are more economical for those who can attend to them properly. Battery technology and economics are evolving rapidly, so it is worthwhile to be informed and open to options.

Good discussion!

"Landfill" was a poor choice of language on my part. We all know that batteries should be recycled properly. In fact, I hauled my last set of batteries from our yacht to a metal recycler and left with $85 cash.

[loft47]

Check with your local Caterpillar dealer. They sell their own proprietary battery line, maintenance free, and extraordinary quality. Used them for many years on my Moho.

[playc]

Great reading and thank you all.

My situation maybe different. Have replaced SRM-24 8/2021 for my '18 22FB. I always go camp with available electricity hookup. In storage I plug in with 110v with timer off and on every 4-6 hours.

1) When plugged in the meter shows 13.6 and 10.9 when off. Is it normal or battery is bad? And when towing it is connected to vehicle.
2) As I camp with electricity hookup. Is it essential for me to replace battery with Lithium Lifeline GPL-27T AGM?

[uncle_bob]

Hi

10.9V suggests the battery likely has run dry. When did you last check the fluid level?

Regardless of the cause, the battery likely is dead. Replacing it with "whatever Costco has on sale" is reasonable in your case. Just make sure it's a deep cycle / RV battery.

For storage, the battery will last a *lot* longer if you simply disconnect it and don't bother with the timer. A $30 disconnect switch would make the "battery off" process pretty simple.

Bob

[Mollysdad]

Originally Posted by DeanAir

I have a 2014 23FB, and it has two Interstate SRM-24 batteries. It is a pain in my area to purchase exact replacements. Can anyone recommend replacement batteries, that are exactly the same physical size?

Exact Replacements?
Unfortunately, Interstate Battery got sold to a Canadian company and the new Batteries are made at a different battery supplier than the old. Better? Worse? It's a rabbit hole to tell what battery is made by who.
IF you're staying with a flooded wet cell (I am too), a good quality group 24 'DEEP CYCLE' should do the trick. Maybe called 'Marine' or 'RV' battery.
Costco seems to be popular, but I hear their batteries have a different warranty. I believe WalMart batteries are made by Excide, the people who made the Old Interstate Batteries.