Dear Dave,
You and others have mentioned batteries using different group number designations. What do those numbers mean?
Second question: I was told that Interstate has different quality levels for their deep cycle batteries. The RV service organization that replaced my house batteries with Interstate claimed that they use a higher grade than those sold at Costco for a lower price. Is this true? —Gary, 2020 Fleetwood Pace Arrow, 34-ft. diesel pusher
Dear Gary,
First let’s look at the classification of deep cycle batteries. Batteries are rated in amp hours, or the amount of time you can run your 12-volt components in your RV. Typically they will also have group ratings that indicate the approximate amp hours available. Group 24 is the smallest with approximately 80 Ah, Group 27 is approximately 100 Ah, and Group 31 is 120. What that means is an 80 amp hour battery can provide 80 amp of 12-volt power for one hour. However, it is recommended that you only draw your deep cycle flooded lead acid (FLA) down to 50%, which means you truly only have 40 amp hours for one hour.
The different group ratings also mean different physical size of the batteries. A Group 24 will be the smallest and is typically 10” L x 6” W x 9” H. A Group 27 is 12” L x 6.5” W x 9” H, and Group 31 is 13” L x 6.75” W x 9” H.
Interstate batteries
According to my local Interstate distributor, Interstate Batteries® markets and distributes batteries manufactured by several different companies and are “branded” as Interstate. It is almost impossible to identify which manufacturer is making them. However, Johnson Controls Inc (JCI) was the original manufacturer, but Interstate recently partnered with Brookfield and Exide.
According to the Costco website, the Costco Interstate battery has the same quality and durability as the Interstate battery offered by authorized Interstate Battery distributors, but just with a different warranty. Keep in mind, anyone can write anything on the internet and there is virtually no way to tell unless you can tear it apart. My local Interstate distributor had no comment other than to weigh the Costco battery and compare it to an identical model at an Interstate distributor. I don’t have a Costco within 120 miles, but I would love to compare!
In any case, I don’t think Interstate is the top of the line when it comes to FLA deep cycle. However, they do have one of the best service networks in the country, which makes them very popular. Also, they have good reviews.
You might also enjoy this from Dave
Can I replace my RV’s two 6-volt batteries with one Group 27 12-volt?
Dear Dave,
I want to replace my two 6-volt house batteries with a single 12-volt deep cycle battery. Both batteries are dead at this point. The battery I’m looking at is an Interstate and I’m told it is 90-amp hours. My questions are: Will this be enough for a day’s travel using only the water pump until plugged in at night, and will the driving keep the battery charged? Thank you for your help on this. —David, 2016 Minnie Winnie 31K
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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Crown, Rolls, and Trojan are high quality deep cycle battery brands. However, lead acid battery ampere ratings (AH), are based on a 20-hour rate. An 80 AH lead acid battery will only deliver 80 AH, when discharged over 20-hours, not one-hour. 80 divided by 20, is 4 amperes per hour to achieve 80 AH from the battery. Discharging at a higher rate (using more than 4 AH/hour) will result in fewer amperes delivered. Often quality battery manufactures will provide a chart of the amperes delivered at higher discharge rates. Most Interstate batteries I see in RVs are not true deep cycle batteries, they are dual purpose starting/deep cycle batteries and less expensive, not made for deep discharging.
Great response! 👍
Had a lightning strike wipe out all the electronics and everything else that uses electrons. NAPA replaced the AGM battery without question.
It’s in the new to us RV. Old RV was totaled by insurance company under the comprehensive portion of the policy.
The group number is purely the physical size and terminal configuration of the battery.
Very few group 27, 31 12V batteries are true deep cycle, vast majority are “marine/RV” hybrids. The only common true deep cycle are the 6v GC2 golf cart batteries.
Thank you, Dave! I have a long way to go before understanding batteries, but this helps tremendously; thank you! Safe travels! 🙂
EnerSys also makes some 12V AGM batteries under the Interstate brand.
I’ve had nothing but troubles with Interstate batteries and will never own another one. For the price and quality I often shop at Walmart and had good success with their products.
I have used two 6 volt Costco Interstate batteries for almost 6 years in our trailer. Those things are beasts! Never a problem. I’ve gone as long as 14 days straight starting at 12.8 ending at 12.0. They live in the garage during winter, charged as necessary.