Group 24 vs. 27 battery

Only drawbacks of a larger size are greater cost, more weight. The gain is mre capacity, if you use it. Larger size doesn't have longer life, unless your use has been overstressing the smaller one. If you need more capacity, go for it. If you don't, then not. 24 to 27 is about a 50% gain, depending on manufacturer and battery technology.

It is a lot like "do I need a bigger gas tank?" Doesn't matter so much if tank is 100 gallons, 50 gallons, 30 gallons if refueling points are 4-10 gallons apart or your bladdef can hold only 12 (or 6, in the case of my subcompact car) gallons worth of driving time.

Back to batteries, Interstate sells a number of different group 24 batteries, for different applications, and lot of those finding their way into RVs are a dual-purpose marine starting-trolling battery, because that one is pretty cheap to make. They have others that are pure starting, and some models closer to being a slow discharge, deep cycle battery, but none that are like a golf cart battery or even a deep cycle Trojan. Interstate is a brand for marketing, buying from different suppliers for different products. How long it should last would depend on just which model you bought, how it has been used, how well taken care of.

I get 3-7 years our of cheap dual purpose batteries (Interstate, Everstart) that are used lightly and maintained with calculated negligence. They serve to keep the refrigerator running during short stops, help the converter run the slideouts, and start the generator. Since my RV is a motorhome, if the batteries go weak I can start the engine and get adequate power for these tasks from the alternator. If I were really using battery power (e.g. boondocking) I would buy the best deep cycle batteries in the largest size I could carry, and take really goo care of them.

So it depends on how you use the battery. If you don't use it, you don't need more than what you have, which is kind of the minimum for a RV: one group 24 deep cycle, or dual purpose if you have to run slideouts.

Get a battery disconnect and use it. Parasitic loads will deplete in two days as previously posted. They are pretty cheap, put it on the negative terminal and unscrew the disconnect when parked. I usually try turning on a light or the tongue jack to make sure it is disconnected.
Good luck.

Be sure to check the water level and add distilled water if needed and then fully charge it on a good charger. Then have it load tested at any auto parts store, this will tell you if you will be OK to wait until next year.

You can pretty much estimate the battery's health by observing voltage and recovery after a load. It's convenient to know what the actual load is but what you're looking for is a bounce back up in voltage.

To really see how the battery is fairing, use a hydrometer. It will tell you if the chargers your're using are getting the battery 100% charged.
With a good charger and a hydrometer you'll increase the longevity of any FLA battery.

FWIW, I replaced my somewhat abused truck battery a couple of years ago. It saw 10 yrs., 1 mo. of service.

Everything will work fine with a weak battery as long as you are plugged in or rolling down the road.
Just need to be strong enough to power the breakaway brake system for 20 seconds during an emergency.
If you keep it well charged this Winter you might get another whole season out of it.

First of all, thank you for the replies!

I usually pull the TT into the back yard and leave it unplugged from shore power for days+ at a time. I'll plug it up for a few hours a week. Sometimes I pull the in-line fuse that was added at the battery...sometimes not.

I pulled the battery last night and charged with my Shumaker (sp?) charger and it seems to be holding a charge for right now. I would greatly prefer to wait until the spring to get another battery. Is there anything that will not work during my last 2 weekends trips if I have a weak battery as long as I am connected to my TV or shore power? Furnace blower? Fridge while running on propane during the trip to the CG? My TT is a Jayco X17C, so no slide...nothing fancy! I hate to get a battery and then let it sit for the whole winter...would rather get one in April so that my warranty starts then!

Thanks!!

I assume you're disconnecting the battery between trips or putting it on a trickle charger? The carbon monoxide detector alone can draw down a battery pretty quickly.

To answer the OP's question, there is no downside to going with the bigger battery if you have the room. You'll get a few more amp hours with the 27.

If all your camping is with hookups,just about any battery will work.In my rig I have triple redundantcy,The TV power at the plug, the house battery,portable genny.All of my camping is far away from crowds.

My 02. Larger the battery the better - but in some rigs you may not have enough room - in my rig height restrictions make type 24 a must. A new type 24 battery cost under $70 at Costco - probably not much more for a type 27. If you dry camp consider adding a second battery. My two type 24's will suffice for about a week if it's not too cold (heater blower consumes alot of battery power).