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Why does RV’s engine battery keep dying in campground?

By Chris Dougherty
Chris Dougherty is a certified RV technician. Here is a letter he received about an engine battery from a reader while he was serving as RVtravel.com’s technical editor.

Dear Chris,
Why does my under-the-hood engine battery keep going dead when I am hooked up to an electric post at campgrounds? I have a Class C Jayco 32-foot motorhome with a V-10 450 gas engine. Funny thing also, I find this out when my propane detector starts screaming. It is wired to the engine battery, too. Oh, and there is a metal bar on the battery that I can lift up to disconnect the power to the one post or leave down and connected. Not sure what that is for; heard lots of opinions. —GiGi

Dear GiGi,
Well, let’s answer these one at a time.

The reason your battery goes dead is that it’s not connected to the coach battery’s charging circuit from the factory, and isn’t most of the time. It is a requirement from the chassis manufacturer that the two 12-volt DC electrical systems remain independent. For this reason, the chassis battery can go dead, especially if there are “parasitic” loads attached to that battery like detectors, steps, stereos and generator start circuits.

The knife blade switch was probably installed to disconnect the battery to keep it from discharging when the coach is not in use. While I’m not sure where you live, another frequent issue is that when the battery is discharged in storage and the outside temperature falls below freezing, the battery is frozen solid and destroyed and will never charge properly again.

The fix for these issues with the engine battery

• Make sure you have a good battery. Many auto parts stores and battery distributors can test it for you.
• Install a built-in battery charging system like the Xantrex Digital Echo Charge, which will automatically transfer battery charging power from the coach battery to the chassis battery while the coach is plugged into shore power, keeping that battery up in addition to the coach battery.
• For prolonged periods in storage, disconnecting the batteries is always a good idea, and if it’s a freezing environment, removing them altogether and storing them in a warm location is best.

Related:

RVelectricity – 12-volt battery dangers (Warning: graphic content)

##RVDT1653

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Mike A Schwab
2 months ago

You can get a USB charger that also displays the voltage to 1 decimal point. I put it in my pickup truck, shows 14.4 after starting, drops to 14.1-13.9 while driving, 12.7 to 12.4 after parking for a while. Caution, the one I bought can’t be removed without disassembly.

J J
2 months ago

I thought most newer motorhomes had circuits that charged the house batteries and the chassis battery from shore power as long as the house battery switch is turned on (not disconnected). Mine does.

I know some people switch the house batteries off when plugged in to avoid “boiling the batteries” but that also keeps the batteries from being charged.

Ron Seidl
2 months ago

A lead acid battery that is not holding a charge might be low on water. Or, it might be in a sulfated condition.

tom
2 months ago

I use a knife switch to disconnect the battery in the towd. Beats having to jump a dead battery. Apparently enough drain to bring the engine battery below starting voltage/current needs.

Bob p
2 months ago

My ‘99 Bounder had a solenoid in the engine compartment That was activated by the coach battery when it was fully charged it would energize the solenoid and charge the engine battery. I was experiencing the same problem and found the solenoid was defective and replaced it and no more dead battery. However it was not a starting solenoid but a continuous duty, starting solenoids are designed for several hundred amps for a short time, continuous duty was 60 amps for several hours. Once the battery was charged the circuit board deactivated the solenoid until it needed charging again.

Dan
2 months ago

I’ve had great luck with battery maintainers. They produce less than 1 amp of charge and automatically stop when a certain charge is reached so they cannot over charge a battery. They’re not the same as a trickle charger. Anyway, a charged battery will not freeze. Two of my maintainers are solar powered, so I don’t need an electric outlet. I also start and run everything for a while through out the winter. I’m also a big fan of fuel stabilizer.

Rock & Tina
2 months ago

My RV comes equipped with a three stage converter and battery isolation manager which ensures my coach and chassis batteries stay charged, happy and healthy regardless of outside temperature as long as I am plugged into shore power. A charged battery cannot be damaged in any way by freezing temperatures. Therefore there is absolutely no reason to go through the effort and hassle involved with removing the batteries for “prolonged storage.”

WEB
2 months ago
Reply to  Rock & Tina

They were referring to parasitic loads draining the battery while in storage (usually without electrics) and then it freezing….