Chassis battery

[Wallacerank]

Why does my chassis battery go dead while stiiing after 2 weeks, new battery?

[Skip426]

Parasitic draws , engine ECM , trans ECM dash radio memory etc.

Disconnecting the battery or having the RV on shore power ( if you RV charges chassis battery on shore power ) when not in use, are the ways to keep it charged up and ready to go.

[DavidEM]

If this were an OEM truck, I would not expect the batteries to go flat after two week. They should be fine for at least three months and usually more.

But RV builders do strange things with the chassis' electrical system and add circuits that can have a large parasitic draw on the chassis battery. Maybe something is wrong but maybe this is just the way it is. I would get someone with a clamp on ammeter to help sort that question out.

David

[Skip426]

Originally Posted by DavidEM

If this were an OEM truck, I would not expect the batteries to go flat after two week. They should be fine for at least three months and usually more.
David

David ; newer vehicles may be better than the ones on the lot at the dealership that I retired from in 2007 ; but in those days 3 weeks was the limit , after that the batteries were too low to start the vehicle . There was a single fuse that wasn't installed at the factory ; that had to be installed for retail delivery or demonstration ; the vehicle would run without the fuse but 95% of the vehicle's electrical features were shut down.

[donr103]

Look into a battery combiner.. that is what I did.. charges off shore power.. when not on shore power.. add 100 to 200w solar panels.. and controller.. cheap and easy to add.. works for me.. I love it.. 100w was plenty at 1st.. but added extra panel .. I got the thin kind of panels that glue down.. no drilling..
Good luck and keep us posted

[twinboat]

If this is happening while on shore power,, Do you have a Lambert LE-415 device back in the bay with the big boy relay. It may not be working.

If your storing it without shore power, get a disconnect switch.

[Cat320]

Originally Posted by twinboat

....If this is happening while on shore power,, Do you have a Lambert LE-415 device back in the bay with the big boy relay. It may not be working....

Or, it could be like my RV, the sensor has to get to 13.3 before it allows the charge to go through from the house batteries to the chassis batteries. If it never gets to 13.3, the charge will never go through.

[Soppy]

Install disconnect switches on the house and chassis batteries. When you are not using your RV make sure the batteries are charged then disconnect them. Once disconnected , they will be good for at least 6 months without needing to be charged.

[THenne1713]

You have some drain, somewhere? Common power thieves are defective dash radios that turn themselves on, charge solenoids welded shut, hidden lights. Have heard of some Entertainment on chassis battery, but usually not? Good Luck.

[terntes]

Parasitic draw. I have two cables going to my ground. One is from the negative battery post, the other goes to somewhere, I have no idea. Put a manual blade disconnect on your battery.

[Mudfrog]

The chassis battery on ours will only last about 2 weeks before dropping too low to crank the engine. Has done this since new.

OP, is this happening while plugged into shore power? Or is it just during storage with no electricity? I ask because my rig 's onboard charger does not charge the chassis battery.

My first attempt at a remedy was to buy a small 5 watt solar trickle charger panel. It helped but couldn't keep up, especially in the winter.

Next was to install a battery disconnect switch. This worked fine and allowed the battery to hold charge for months. Only thing, I disliked that this removed and applied power to the engine's ecm every time the switch was maneuvered. May not have hurt anything but I still didn't like it.

I finally got to run power out to where our rig is stored. I use a weekly timer to power up the rig which keeps all the batteries charged. The onboard does the coach batteries and a separate stand alone charger takes care of the chassis battery.

OP, do you have access to 120 vac power where your rig is stored?

As far as the battery goes, it may or may not be bad. Letting a standard wet cell battery go dead isn't good for it. Letting it go dead several times is very hard on it and will lead to an un-useable battery. You should have it load tested to be sure.

[Gary RVRoamer]

Modern motorhomes have factory-designed parasitic draws on the chassis batteries, e.g. the powered entry steps, LP detectors, and slide out motors. All done per RVIA standards. We can debate the wisdom of that, but it's a fact. Then there is the likely fact that any RV that has had some aftermarket stuff added probably has more parasitic draws, either intentional or accidental. Things get added for convenience without thinking about the potential impact on the battery.

[tap4154]

Mine was going dead after less than a week, sometimes in a couple days. I finally figured out that an unmarked rocker switch on the driver side A pillar was the mirror heater switch, and it was always active even when the ignition switch is off. After I learned that and kept the switch turned off I haven't had a problem since. However I wired an SAE connector into the grill to the chassis battery, and keep a little 10 watt solar panel on the hood. That's kept my chassis battery charged as it sits facing south in my backyard. I also wired in an ultrasonic rodent repeller under the hood, and even with that operating the battery stays up with the little 10 watt panel hooked up.

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[THenne1713]

Just remembered some reporting MIRROR HEAT not turning off w/ IGN=OFF?