Chassis battery charging

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Rich Bonett

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Joined
Dec 20, 2010
Posts
3
Hi all--
I have 2006 Thor Presidio diesel pusher.We have had it for about two years and absolutely love it. We have a few 'bumps in the road' and here is a new one-

My chassis batteries do not seem to be charging when the engine is running. We went on a long trip a few weeks ago and the low voltage alarm in the dash sounded. I pushed the battery boost button and it went off. I let go of the button after a few minutes and it soundec again. I replaced the batteries at the campsite we were at. On the way home the same thing happened again after a few hours of driving. When we got home we plugged the bus in. I checked the voltage after a few days and got the following:
Plugged in-13.4 volts
Unplugged-13.35
Engine running gen off-12.5 and dropping
Engine off gen on--12.75 and rising

Engine off,genoff,unplugged-13.1(equal to house batteries)

Engine off,gen off, plugged in-13.4 volts



Any suggestions will be greatly appreciated.

Thanks

Rich Bonett
06 Presidio 39b
workhorse chassis
cummins 330
04 trailblazer toad
 
Rich:

The low voltage alarm on the dash is usually low voltage on the truck side.

If you mean house generator off the engine generator should have been charging while the truck engine is running at 1000rpms or so. Start it up again and check the voltage of the house batteries AND the chassis batteries. If the isolator is working properly the voltage should be 13.2 or so on both sets of batteries. If both sets are down to 12.8 or lower the truck generator or voltage regulator is not working properly.

If the truck batteries are 13.2 or so and the house batteries are 12.8 then the isolator or a connection to it are bad.
 
From your measurements, I would conclude that your Engine Alternator is not charging your batteries while running.  I would make a measurement at the Alternator with engine running and see if you have anything there.
 
Thanks for the replies. I will check voltage at the alternator this morning (If I can find it) These pushers do not make engine checks easy.I did check the house batteries at each measurement and they were 13.2-13.4 at each check. Only the chassis batteries changed. Wll post alternator results soon.

Thanks

Rich
 
Checking the truck battery voltage at the cables will give you the same results as the alternator. The Motorhomes isn't plugged in to shore power is it
 
:)Thanks all.
After losing sleep, researching online and bothering you guys I checked the alternator and after realizing it was the air conditioning compressor I looked again and found the real alternator. The red cable connection was very rusty so I took it and the black and the small brown wire off, cleaned them and put them back on. After starting the bus I got a reading over 14 volts and the dash indicator showed the same.I guess as complicated as these machines are sometimes it really is the simple stuff that causes problems.
Thanks again for the suggestions.

Rich
 
My husband and I have a 2000 American Dream.  He just came in from measuring the voltage across the house batteries and the chassis batteries.  The house batteries are running around 12.6 and the chassis batteries are measuring 7.5.  We are using a 30amp receptacle here at the house.  Is that enough to give the chassis batteries a charge?  I feel like we might just be too dumb/green to own this behemoth!  Any and all advice is well received.  Would not having a good charge on the chassis batteries cause the coach to die while driving?
 
You might want to start your own topic in the  Tech Talk section to get more exposure and notice from the folks here most familiar with your particular RV.

I can tell you, however, that 7.5 volts is NOT enough to start your motorhome, or to even keep it running.  If you are indeed plugged into a source of 120vac power, neither of the voltage readings that you quoted is indicating that the batteries are being charged.  Your rig is designed to charge both the chassis and house batteries when plugged to shore power.  The voltages you should be measuring would typically be 13.2+ VDC.

It might be that the charger (converter or Inverter/charger) is turned off or simply nonfunctional.  There are switches (usually) located near the entry door that should be ON to allow the batteries to remain connected for charging purposes.
 
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