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Ask Dave: How to tell a house and chassis battery apart

Dear Dave,
What is the best way for me to determine which battery is the coach battery and which is for the motor? Is it better to replace it with an AGM or lithium? Lithium is so expensive and I am not sure if the cost is really worth it. Thanks, Dave. —George, 1997 Winnebago Warrior 25RU

Dear George,
Wow, that was the last year I was at Winnebago Industries (1997). The Warrior was called the “D” Series. It was a price leader made to compete against the Fleetwood Flair and other basic models. I remember most of the features, and Winnebago still has some really good documentation even on a model that old. According to the website, the house and chassis battery are both located in a tray in the engine compartment (4).

The chassis battery was a 660 cold cranking amp (CCA) battery, and since it was a Chevrolet chassis, it was originally a Delco. However, 25 years later, it would have been changed by now. You should be able to identify it by the description of CCA and typically side posts. Also, the positive cable should go to the starter.

Telling a house and chassis battery apart

The house battery should be labeled as a deep cycle battery with an Amp Hour (Ah) rating. The positive cable would go to a Battery Isolation Management solenoid (BMI). And, once again, this would have been changed several times.

Keep in mind, this is what was installed originally and should also be the same now. That being said, I have learned never to say “never” or “always” when it comes to RVs. I have found CCA batteries installed where deep cycles are required and deep cycles used for starter batteries. If you use a starter battery in a deep cycle application, it will not last long as they are meant to be charged all the time by the alternator. Draining and recharging will ruin them.

On the other hand, if you use a deep cycle battery to try and start your engine, it will eventually sulfate and not have enough cold cranking amps to start the unit.

Another way you can tell which battery is the deep cycle is to plug the unit into a 120-volt source. The converter should kick in to either charge the battery (if it is low, at 13.6-volts) or provide a maintenance charge of 13.2 volts instead of the 12.6 volts of a normally charged battery.

What’s the best battery for my RV?

With all that said, the best battery for your rig depends on your RV lifestyle and especially how often you dry camp or camp without being plugged into a campground or electrical source. If you do not dry camp, then a normal lead-acid battery is fine, as the converter will provide power to run your 12-volt items. An Absorbed Glass Mat (AGM) battery is a step up. It does not sulfate as much and requires less maintenance. It will last longer but cost about twice as much. I would only consider lithium if you dry camp a lot as they are 5-6 times the amount of money, as you mentioned.

Also, you’d need to verify your converter, inverter, or solar charging system is compatible with charging lithium. Check out this article about evaluating Lithium Batteries.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

Read more from Dave here

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