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Old 12-18-2015, 08:25 AM   #1
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Chassis battery question

2008 Berkshire.

I've noticed that my chassis batteries are running down when parked, even when I'm plugged into shore power.

I've also noticed that my Aux Start button is lit very dimly...and flashes every so often. (This is when parked, engine off, and plugged in or not)

This last time I parked, I turned the battery disconnect at the chassis batteries to off.

Last night I noticed something strange: The Aux Light button was completely off (no dim light and no flashing) and the 12v power socket next to the leveling control panel was off.
This morning, those are both back on...and nothing changed overnight!

Do I have a draw somewhere on the chassis batteries?
What is making that aux button light up dimly? And blink?

I've inspected my batteries and they look ok...a tiny bit of corrosion on one of the negative terminals, but not very much at all.

When I start up the engine, I usually get a "Low voltage" indicator until it runs for a few minutes. Sometimes that's as low as 11.2v and sometimes is 12v or so.

I have a store-bought trickle charger installed and it had been connected to the chassis batteries and plugged into the block heater outlet so that it would charge when connected to shore power, but I can't measure any voltage across the two leads on that when its on, so I don't even know if it's working. I left the leads disconnected after testing them.

Any ideas on the Aux Start light or where I might be getting a drain?

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Old 12-18-2015, 08:42 AM   #2
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The battery disconnect switch will not turn off the propane, carbon monoxide, or smoke sensors and they will continue to draw power, although minimal, from the battery.

Joe R.

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Old 12-18-2015, 08:55 AM   #3
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Ok, good point.
But shouldn't the chassis batteries charge after the house batteries are full, when connected to shore power?

Any ideas on the dim/blinking aux start light?

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Old 12-18-2015, 09:17 AM   #4
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You should measure the voltage of each battery. You may have a bad cell in one. How old are your batteries?
2011 Berkshire 390-rb-40, upgraded tires and front axle airbags, 2012 Jeep Wrangler 2 door, Blue Ox baseplate and BlueOx aladdin tow bar, Blue Ox Patriot brake system, wiring run through right frame rail and homemade led taillight bar.FB.
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Old 12-18-2015, 09:18 AM   #5
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There was a thread some time ago on the blinking aux light blinking. Many of us have this happen. My understanding is when the house batteries are fully charged then the light will light and the chassis battery is getting charged. Why are you turning off your chassis batteries anyway? We leave ours on all the time. We also get at times the low voltage when starting the engine but goes away shortly after engines runs. Also the steps and some other things run off your chassis batteries, found this out when the house batteries when changing out those batteries.
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Old 12-18-2015, 09:38 AM   #6
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I'm checking on the age now. I believe they have been replaced once. When I measured voltage (while connected) I was showing around that sounds good.

Hmm, I'll try to find that thread on aux start. I noticed that and thought it might be related to battery drain, but maybe not.
I usually leave my chassis batteries "on" as well...I only turned the disconnect this last time I parked to see if that made a difference on the battery drain. We'll see tomorrow when I start up! :-)

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Old 12-18-2015, 10:10 AM   #7
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You will get the low voltage message when you start the engine and the weather is cold. It is caused by the engine heaters drawing from the batteries to heat the incoming air. We all get that message and you should also see needle on the amp gauge on the dash go up and down for a while after you first start the engine.
Tom and Margaret
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Old 12-18-2015, 10:14 AM   #8
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Most diesel alternators don't charge right after starting.
Grid heaters and glow plugs take a lot out of the batteries.

Low charge light is normal right after startup.

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Old 12-18-2015, 11:02 AM   #9
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Ok, thanks everyone for the replies! Sounds like it's functioning as it should be!

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Old 12-18-2015, 11:20 AM   #10
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You may want to note that when starting the Diesel generator when cold out holding the inside generator switch in the shut off position activates the glow plugs (like the preheat switch on the generator) for easier starting.

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