| Re: [GMCnet] Engine battery monitor [message #76022] |
Mon, 08 March 2010 17:54  |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma:
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Senior Member |
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Hi Gene, I'll probably take you up on your offer in June. Thanks. :-)
For now, I do have a DVM, and read 12.37v at the battery after sitting for ~30hrs since last driven (though I am hooked to shore power and have a combiner, so maybe that messes up the reading per discussion below). I haven't tried to hook up a DVM to see what it does while driving. I'm guessing I could do that through like the cigarette lighter?
Dan as to your comments about watching the house battery voltage while driving, I'm guessing you must have (like I do) a combiner, but I'm still a bit confused about how they work, but my best understanding is that if the engine is running and the alternator is charging at say 14.5v, then assuming the house batteries are lower than that, then amps will flow into the house batteries to keep them charged. Is that right? Also, doesn't it go the other way too? That is, if my engine battery is 12.37v, and I'm hooked to shore power and my charger is feeding 14+ volts into my house batteries, won't amps also be flowing through the combiner to charge the engine battery?
Ken as to your question about what I'm trying to monitor, I'm a little fuzzy about that myself. Mostly I'd like some advance notice of problems before they destroy another battery/alternator set, assuming there could be some component or connection that is the root cause of all this other than just a bad rebuilt alternator. I'm just sort of flailing in terms of figuring out what to measure to give me that. I like Dan's experience with just watching the voltage while driving and will definitely hook up something to do that. That would be a lot easier than hooking up a shunt to monitor amps.
Thanks to all for the input.
J Rabe
76 Palm Beach
Portland, OR
> Date: Mon, 8 Mar 2010 13:31:21 -0800
> From: mr.erfisher@gmail.com
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] Engine battery monitor
>
> I am somewhat familiar with your coach, (as you know). I tried to work on
> the coach for the PO but by that time, he had lost confidence in the GMC and
> had it up for sale. I know the PO did none of his own work, and had no
> idea what was done to his coach, other than he had problems.
>
> It is not unusual to get several bad rebuilt alternators from part houses
> since they never replace the stator windings and most of the 30 year old
> alternators need all the mechanical, electrical, and stator windings
> replaced.
>
> Here are my recommendations. (click on the links)
> *
> VOLTMETER*
> You can learn everything you need to know about the alternator and battery
> condition with a volt meter. (center terminal of diode isolator should be
> 14.7 with engine running)
> Buy a low cost 3-1/2 digit digital voltmeter (harbor freight for less than
> $10) . I like the Radio Shack one, because it will turn it's self off when
> you forget to turn it off.
> http://users.sfo.com/~eagle/instr.html#digital
>
> *APC CABLE*
> Install an APC cable so your alternator light does not glow dim and a bad
> alternator will not burn up the wires behind the dash.
> http://gmcmotorhome.info/APC.html
>
> *COMBINER*
> Install a combiner across the diode isolator. This will charge all
> batteries from all sources and will compensate for several problems the
> diode isolator may have.
> *http://tinyurl.com/ye5jato*
>
> *BATTERY CONDITION*
> A charged battery at rest should be about 12.5 volts
> A battery at rest at 12 volts, is 1/2 discharged
> A smart charger should be holding your charge rate at 13.6 volts.
> *http://tinyurl.com/yl83xs6*
>
> and finally, wait until middle June, and come back to Florence, Orgn (when I
> am back there)and we will work on your GMC together;>)
>
> gene
>
>
>
>
>
>
> My coach has a history of electrical system failures, including 3
> > alternators and 2 batteries in the 3 years prior to my getting the coach. I
> > didn't get a clear answer from the PO as to any firm conclusions explaining
> > the repeated problems, other than speculating about just bad luck to get
> > two, bad rebuilt alternators in a row.
> >
>
>
>
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://gmcmotorhome.info/
> Alternator Protection Cable
> http://gmcmotorhome.info/APC.html
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