Chassis battery vs house battery vs generator - what works on what?

Hello all!  We are so thrilled to have found this forum.  We are posting under the "dumb question" category (LOL).  We are VERY new to RVing.  Over the years we have gone from a pop up, to a travel trailer, to a 5th wheel, and now to a 2007 Fleetwood Bounder 35E. 
Question - we are confused as to which things work on what kind of power!  While in our driveway with the motor running, the lights are very dim and the TVs won't come on.  Once on generator power, everything works fine.  Do we have to have the generator running while driving just to watch TV and have bright lights?  Is the "house battery" and/or chassis battery power not enough?  Or do we have an issue? 
Our chassis battery is new and showing 12.7 volts when tested.  The house batteries show 10v when tested. 
Thanks so much for any help offered! 
Meg B 

At 10 volts, your house batteries are probably shot, at the very least, badly in need of recharging.  Your batteries should not normally go below about 12.3 volts.  Check the water level in the house batteries and put them on charge for several hours.  If you can't plug your motorhome into shore power put a regular battery charger on them.  Then have them load tested to determine if they are still healthy.


As for the lights and TV not working with the engine running, many motorhomes will charge the house batteries while the engine is running, but not all.  Perhaps someone can tell you if the Bounder is supposed to or not.  There may be a failure there or maybe not.


I do not know for sure, but in a 2007 Bounder, the TV is probably on an inverter circuit.  An inverter provides 120 VAC from the 12 VDC house batteries IF the battery voltage is high enough.  10 volts is not high enough for the inverter to work.


A MH like yours has quite a bit of "parasitic" power drain when everything is turned off.  It will eventually drain the batteries if it sits long enough.  There is a battery disconnect switch somewhere (probably near the exit) that will shut off most of this drain, although, still not all.  Your best bet is to get set up where you can plug into your home power or storage location power.  To do so, you'll need a plug adapter to convert from a 50 amp connector to a standard 15 amp plug.  Your MH has a converter that converts 120 VAC from shore power or generator power to 12 VDC and also charges the house batteries.  It seems yours is functioning since everything, including lights and TV, work with the generator running.

Hello Tom & Joyce, 

Thank you so much for your detailed response.  We appreciate it.  Your Westie is adorable! 

We hooked the house batteries up to a regular battery charger a few days ago and did a "slow & low" charge on them.  They showed 12 v but went back down to 10 v (as per my question).  We will check the water level though  - duh, didn't think of that!  It appears to be a brand new battery.

You are exactly right - we had both battery disconnect switches off, but it still drained the batteries after a week or so of sitting.  So apparently there are still things putting a drain on the batteries - definitely parasitic, as you stated.  We'll connect to our house power and see if that helps!

We used a regular battery charger on the chassis battery TWICE and it drained back down so quickly that it wouldn't start a couple days after the charging was complete!  We had a brand new deep cycle battery from our previous camper in our shed, so we replaced the chassis battery with it, which seemed to solve the chassis battery problem.  We bought the camper used and apparently that battery needed to be replaced.

We are still in the process of reading through all the manuals(!) and need to learn more about the inverter.  Someone else on the forum mentioned that Fleetwood has great customer service, so we plan to call them today.  We are taking our first "real" trip soon and want to be sure everything is in working order.

Thank you very much for taking the time to respond! 

Bounders do indeed charge the house battery via the engine alternator. And also the chassis battery from the house system when shore or genset power is active (but not until the house batteries reach near full charge).

Test your house battery for a bad cell.  It sounds as though it may have been damaged and won't hold onto a full charge. Usually a reading of 12.0 volts is a battery that is about 50% depleted. At 10 volts the battery is near completely dead.

To try to answer your initial  question,

CHASSIS BATTERY  powers the "truck" part of the RV only, i.e. starter, dash radio, head lights, etc.  It normally powers nothing in the "house" to make sure the engine will start when you are ready to go.

HOUSE BATTERY  powers most interior and exterior lights.  It powers leveling jacks, slide outs, water pump, most vent fans and other 12V items.  It is also REQUIRED for control circuits to operate water heater, refrig, furnace and A/C.  120V may be used to power these appliances, but the 12V is still needed.

If you have an INVERTER, which inverts 12VDC to 120VAC, then house batteries will power some 120V receptacles, such as for TV.  Generally, high draw items like hair dryers, microwave, coffee pot and A/C can not run on battery power.

SHORE POWER / GENERATOR are essentially the same as far as what works on this power.  This powers all 120V items - within the limits of the power available. The CONVERTER converts 120VAC to 12VDC to power all 12V items.  It also will charge the house and chassis batteries as Gary stated.

If you are plugged into 30A service, obviously you can not run 45 amps of stuff.

I hope this helps.

The house (coach) batteries usually feed the GENERATOR.

The house (coach) batteries usually feed the GENERATOR.

Click to expand...

I don't think there is enough consistency across manufacturers, models and years to say "usually" about this subject. A substantial number of motorhomes use the chassis (engine) battery to start the genset, others use the house battery, and a few have an independent battery for the genset.

Gary RV Roamer said:

I don't think there is enough consistency across manufacturers, models and years to say "usually" about this subject. A substantial number of motorhomes use the chassis (engine) battery to start the genset, others use the house battery, and a few have an independent battery for the genset.

Click to expand...

If by any chance you do have the great option of "AGS" for automatic generator start" or similar to that, how would the GEN know when to start and charge your house batteries ?

The AGS battery SENSOR is connected to the house batteries. Has nothing to do with which battery the generator starter is connected to.

grashley said:

To try to answer your initial  question,

CHASSIS BATTERY  powers the "truck" part of the RV only, i.e. starter, dash radio, head lights, etc.  It normally powers nothing in the "house" to make sure the engine will start when you are ready to go.

HOUSE BATTERY  powers most interior and exterior lights.  It powers leveling jacks, slide outs, water pump, most vent fans and other 12V items.  It is also REQUIRED for control circuits to operate water heater, refrig, furnace and A/C.  120V may be used to power these appliances, but the 12V is still needed.

If you have an INVERTER, which inverts 12VDC to 120VAC, then house batteries will power some 120V receptacles, such as for TV.  Generally, high draw items like hair dryers, microwave, coffee pot and A/C can not run on battery power.

SHORE POWER / GENERATOR are essentially the same as far as what works on this power.  This powers all 120V items - within the limits of the power available. The CONVERTER converts 120VAC to 12VDC to power all 12V items.  It also will charge the house and chassis batteries as Gary stated.

If you are plugged into 30A service, obviously you can not run 45 amps of stuff.

I hope this helps.

Click to expand...

FYI on my Jayco the Chassis battery also powered the auto entry steps. Having them go in and out with the door killed our chassis battery which was NOT recharged by shore power....

The entry steps on a motorhome are typically powered from the chassis battery. In recent models, the slide motors may be as well.