Battery terminology can be confusing but it’s really important!
Hey Mike,
I have two 12-Volt batteries on my 2018 Cedar Creek 5th wheel. The dealer is telling me I should replace them with 24V AGM batteries.
I heard that my Ram pickup truck would not be able to charge the 24-Volt batteries while driving. Is this true? Are there any other concerns I should be aware of going from 12-Volt to 24-Volt batteries? —John Morra
Dear John,
I think you’re confusing battery voltage with the battery Group size…
Instead of 24V are you sure they didn’t mean a 12-volt Group 24M battery? If so, that’s not a horrible idea, but it may not give you the best performance.
Many (most?) of the Group 24M AGM batteries I found are rated for both Amp-Hours and CCA (Cold Cranking Amps), which usually indicates a dual-use battery that can function as a starter battery as well as a deep-storage battery.
A true deep-storage battery isn’t rated in the CCA needed to provide the huge starting currents required when starting a gas or diesel motor. It will only have a 20 Hr rating. See below…
You need deep-cycle batteries rated for a 20hr discharge rate
What you’re looking for in an RV house battery is one that’s rated for a 20-hour discharge rate. This Renogy battery is rated for 100Ah/20Hr.
So instead of being rated for CCA (Cold Cranking Amps) like an engine starter battery, it’s designed to provide 100 amp-hrs of current over a 20-hour discharge time. Hence the 100Ah/20Hr rating on the battery.
There’s a big difference between a 24M and a 24V battery
But what if they really did suggest a 24V battery. If so, that’s a very bad idea. Your existing dual 12-volt batteries are connected in parallel, which provides 12-volt DC to your RV’s electrical system. A 24V battery is indeed 24 Volts.
To convert your RV’s electrical system to 24 volts would require a lot of changes to your inverter, lighting, control systems, and any slideout motors, etc.
And, yes, your tow vehicle would not be able to charge the RV with a 24-volt battery system without a lot of extra technology such as a DC to DC charger.
Don’t do it!
There is simply no good reason to change your RV from a 12-volt battery system to a 24-volt battery system, and lots of reasons not to. So, I hope your dealer meant a Group 24M, which is the size of a Marine-rated 12-volt battery, not a 24V (24-volt) battery.
OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.
Let’s play safe out there…. Mike
