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Old 06-09-2018, 03:26 AM   #1
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THOR #7419
Chassis battery

Have a 17 Quantum C. Sitting at a park 2 weeks connected to 30A shorepower. Battery switch in use position. Reading 13.2 on volt meter in float charge.


House batteries ok. Chassis battery dead when i tried to start engine. Why? Any ideas?
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Old 06-09-2018, 11:10 AM   #2
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I was told directly by Thor that class C coaches don't charge the chassis battery from anything other than the alternator. I'm going to add a disconnect to mine and possibly a battery minder . You could run a battery minder off the coach outside outlet for the chassis battery.
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Old 06-09-2018, 01:20 PM   #3
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I am confused why would sitting two weeks anywhere make your engine battery go dead without being on a charge. What draw does it have if your on shore power. My C sits for weeks at a time at the house and never have an issue with rig battery . My radio runs off house battery so where is the draw if the engine is shut off. Even with the house battery running what is the draw?
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Old 06-09-2018, 01:23 PM   #4
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They probably keep the chassis battery "isolated", so that you don't inadvertently run it down...
(But you can tie in the coach batteries for some help with the starting chores: should the need arise...)


If the engine is running: you also get sine charging in the coach batteries...
But the reverse isn't true?
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Old 06-09-2018, 01:46 PM   #5
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If you have one of the infamous Harris batteries that seem to die quickly, you may want to change it for a much better name brand.
Also, add a knife switch disconnect to your neg. post to stop parasitic draw when in storage.
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Old 06-09-2018, 01:49 PM   #6
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THOR #9522
Quote:
Originally Posted by Bob Denman View Post
They probably keep the chassis battery "isolated", so that you don't inadvertently run it down...
(But you can tie in the coach batteries for some help with the starting chores: should the need arise...)


If the engine is running: you also get sine charging in the coach batteries...
But the reverse isn't true?
Not according to Thor for their Cs. As yes, Cs no.
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Old 06-09-2018, 01:53 PM   #7
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THOR #10354
Battery dies

Check the obvious: Headlight , parking lights, ignition key/accessories. Then check the alternator for a shorted diode (there are 3). Take the chassis battery terminal off and measure the current flowing in the ignition off position with a volt/ohm/ammeter. The battery might also be at fault with a shorted cell due to age or just failure.
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Old 06-09-2018, 01:56 PM   #8
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I don't understand this at all. The battery in my car and F150 can sit for months and still start the vehicle. I have never had to worry about this in any of my vehicles. Why does it happen in an RV?
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Old 06-09-2018, 02:14 PM   #9
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I don't understand this at all. The battery in my car and F150 can sit for months and still start the vehicle. I have never had to worry about this in any of my vehicles. Why does it happen in an RV?
Obviously, something is wrong. This is not normal as you have stated.
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Old 06-09-2018, 07:42 PM   #10
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Originally Posted by mcr1010 View Post
If you have one of the infamous Harris batteries that seem to die quickly, you may want to change it for a much better name brand.
Also, add a knife switch disconnect to your neg. post to stop parasitic draw when in storage.
It's a Ford Motorcraft battery which are usually quite reliable.

Already replaced the Harris house batteries with Trojans.
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Old 06-09-2018, 07:56 PM   #11
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You can try and track the parasitic draw down, but I would throw in the towel and put a knife switch on it and be done with it. That is what I had to do.
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Old 06-10-2018, 01:33 AM   #12
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THOR #10965
Is it possible that the solenoid connecting the chassis to the house battery is stuck in the closed position so the charge is being drawn down?
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Old 06-10-2018, 01:52 AM   #13
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Originally Posted by Bogie View Post
Is it possible that the solenoid connecting the chassis to the house battery is stuck in the closed position so the charge is being drawn down?
Is that the solenoid that comes into play wnen the emergency start switch is engaged?
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Old 06-10-2018, 05:06 PM   #14
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THOR #10965
Yes. On mine it also charges the house battery after the engine is running for 12 seconds.
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Old 06-10-2018, 05:23 PM   #15
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Originally Posted by mcr1010 View Post
You can try and track the parasitic draw down, but I would throw in the towel and put a knife switch on it and be done with it. That is what I had to do.

So did I...


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Old 06-10-2018, 05:32 PM   #16
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Some vehicles, by design have a parasitic electrical drain, in some cases a computer that runs diagnostics even when the ignition is off. One of my cars came with a paragraph in the manual that says, never leave parked for more than 28 days, as the battery will be drained enough to not allow it to start. My former DP would drain both chassis batteries in two weeks, until I installed a small intelligent charger connected to the chassis batteries, that would power up when ever the generator ran or it was plugged into shore power.
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