So What charges What in battery land

boybach

boybach

Well-known member
Dec 9, 2020
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Ok, I was under the impression that Onan charged house and chassis batteries but I now see that it only charges house bank.

Does the alternator charge just the chassis battery or does it charge both?

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
The alternator charges BOTH battery systems (engine and house) through the isolator.

The Onan (or shore power) charges the house batteries through the 120vac to 12vdc converter.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Yes, the alternator charged both banks through the battery isolator or by means of a combiner.

The Onan provides 120 volts to the converter (battery charger) which generally only charges the house battery bank. However some converters have the ability to charge one or two more banks while keeping them isolated from the house battery bank.
My Statpower Trucharger has that ability. I just had to run a wire from the second set of charging terminals to my engine battery.

Emery STORA

>
> The alternator charges BOTH battery systems (engine and house) through the isolator.
>
> The Onan (or shore power) charges the house batteries through the 120vac to 12vdc converter.
>
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
 
> The alternator charges BOTH battery systems (engine and house) through the isolator.
>
> The Onan (or shore power) charges the house batteries through the 120vac to 12vdc converter.

Thanks Ken, that's clear now.

cheers

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
> > The alternator charges BOTH battery systems (engine and house) through the isolator.
> >
> > The Onan (or shore power) charges the house batteries through the 120vac to 12vdc converter.
>
> Thanks Ken, that's clear now.
>
> cheers
>
> Larry

There are other non-OEM configurations / options available that are in my opinion of dubious benefit. The description that I gave you is the way that
GM built it and do not reflect PO later changes.

I would look at replacing the converter with a stepped voltage one so you can leave shore power plugged in long term without over charging and
destroying batteries. They are getting very expensive these days. I like the Progressive Dynamics ones, but there are other brands out these that I
have no experience with.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
For $70 you can have the 125VAC to 12VDC converter charge both battery banks by adding a Yandina combiner across the isolator battery terminals and
ground. Simple elegant solution without a bunch of reengineering and cost.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
40 years of who knows what makes me want to add “verify your set up”.

Once you know what a combiner, isolater and charger in several forms are, you can probably reverse engineer your current setup. Factory used an
isolater, it is what allowed alternator to charge house and engine batteries. Onan did not charge engine battery in this setup.

Combiners were popular to add because they offer charge to occur to both systems from either direction and can be installed with or without leaving
the isolator in place. It is worth figuring what you have on this question because it changes what happens in failure mode

There is a possibility of a more marine style setup with a manual switch for 1,2, or both. Not too common but easy to spot if looking around

My two cents, with the takeaway being knowledge of your actual coach is the key.

--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
 
Ok lads, thanks for the info. My setup is standard, the Onan charges the house and the alternator charges both. I have an IOTA 55 converter on my rig
BTW.

One more thing - in the standard setup, if one battery is low, will the other try to equalize and bring the other up while drawing itself down a tad?

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
> Ok lads, thanks for the info. My setup is standard, the Onan charges the house and the alternator charges both. I have an IOTA 55 converter on my
> rig BTW.
>
> One more thing - in the standard setup, if one battery is low, will the other try to equalize and bring the other up while drawing itself down a
> tad?
>
> Larry

Larry,

That is exactly what is not supposed to happen. With the OE diode isolator, if one bank is way dead, it may take up charging first because the system
can't do both with the standard hardware. This is even worse if you have a combiner.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
If by two batteries you mean one house and one engine battery, then the answer is they will not discharge each other because the isolator sits between
them providing separation.

If you mean 2 house batteries in parallel, this is something you do not want to do. The parallel ones will discharge to the level of the lower one.
What is worse is the potential exposure to explosion if one of them shorts just one cell. A better solution is two 6 volt batteries in series for
extra storage capacity.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
I was just talking about the house and chassis systems, I just have a single house battery.

Larry
--
Larry - Victoria BC -

1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
 
OK, then the two batteries are isolated from, each other by the isolator and will the batteries will NOT deplete the charge from each other.

Ken B.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
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