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So What charges What in battery land [message #365581]

Tue, 20 July 2021 22:44

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

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 ex-Palm Beach "Ol' Leaky" 40,000 miles, PO said everything working but forgot the word NOT. Atwood helium fridge, water heater & furnace. SS exhaust system, Onan, Iota Converter, R134A, New fuel lines & heat exchange hoses

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Re: So What charges What in battery land [message #365582 is a reply to message #365581]

Tue, 20 July 2021 23:14

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

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

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Re: So What charges What in battery land [message #365584 is a reply to message #365582]

Tue, 20 July 2021 23:37

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

Ken Burton wrote on Tue, 20 July 2021 21:14

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

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[GMCnet] Re: So What charges What in battery land [message #365586 is a reply to message #365582]

Tue, 20 July 2021 23:30

stu@97381.com, Emery

Messages: 232
Registered: June 2020

Karma: 2

Senior Member

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

> On Jul 20, 2021, at 10:14 PM, Ken Burton wrote:
>
> 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
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Re: So What charges What in battery land [message #365587 is a reply to message #365584]

Wed, 21 July 2021 03:54

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

boybach wrote on Tue, 20 July 2021 23:37

Ken Burton wrote on Tue, 20 July 2021 21:14
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

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Re: So What charges What in battery land [message #365589 is a reply to message #365581]

Wed, 21 July 2021 07:17

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

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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

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Re: So What charges What in battery land [message #365590 is a reply to message #365581]

Wed, 21 July 2021 07:17

Tilerpep

Messages: 404
Registered: June 2013
Location: Raleigh, NC

Karma: 7

Senior Member

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

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Re: So What charges What in battery land [message #365597 is a reply to message #365581]

Wed, 21 July 2021 11:19

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

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

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Re: So What charges What in battery land [message #365603 is a reply to message #365597]

Wed, 21 July 2021 12:36

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

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boybach wrote on Wed, 21 July 2021 12:19

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

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Re: So What charges What in battery land [message #365605 is a reply to message #365581]

Wed, 21 July 2021 13:57

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

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

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