Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM. Today I discuss a 24-volt battery.
I heard that my Ram pickup truck would not be able to charge the 24V batteries while driving. Is this true? Are there any other concerns I should be aware of going from 12V to 24V batteries? —John Morra
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 CCA needed to provide the huge starting currents required when starting a gas or diesel motor. It will have a 20Hr rating. See below…
You need deep-cycle batteries rated for 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.
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There’s a big difference between a 24M and a 24V battery
But what if they really did suggest a 24-volt 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.
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. 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 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….
Send your questions to me at my new RVelectricity forum here.
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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