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| [GMCnet] Battery? [message #213141] |
Wed, 03 July 2013 11:07  |
Anonymous
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I'm working through our new to us 73 26' coach and it has 2 automotive
batteries 1 for the engine and 1 for the house. Who makes a good deep
discharge battery for the house? My Dad has bought several "deep cycle"
batteries for his house boat and they don't seem to be any better than
the typical automotive batteries, they last a couple years then die.
What are the advantages / disadvantages of a single 12v battery vs. 2 6v
batteries in series vs. 2 12v batteries in parallel.
Most of our use will be off grid. Coach has a 4K Onan.
Thanks
Brian
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| Re: [GMCnet] Battery? [message #213144 is a reply to message #213141] |
Wed, 03 July 2013 11:25  |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Well, if you want a battery that will really last and can take a high charge rate try this:
http://www.northstarbattery.com/1.0.1.0/191/SMS_AGM_400_(SES-542-99).pdf
185ampHr capacity and at 4.9" wide you may be able to install 2 of them.
We use Northstar batteries at remote radio tower sites and they beat all others hands down. Not cheap but they hold their capacity and can take really deep discharges. I think that one is about $400.00
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
[Updated on: Wed, 03 July 2013 11:25] Report message to a moderator |
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| Re: [GMCnet] Battery? [message #213149 is a reply to message #213141] |
Wed, 03 July 2013 12:21 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Sir: I`m kinda different than most. I do have a BIL at the truck stop where I did business for many years and he sold me used group 31 big truck core batteries for $10 (what they give for trade ins). He use to just swap cores with me free but says he has to sell them to me now per bosses orders but did not want my cores. Big trucks have 3 or 4 batteries depending on engine size and are usually replaced as a set even if only 1 is bad. I have a battery load testor from HF. When I need batteries I test them and if they will hold a load over 11 volts I will use it. I have 2 in my 23', 1 for engine and 1 for house as it came from factory except they are 1150 cca. Usually I am plugged in upon destination but have run the furnace, 12v fridge, lights overnighting at rest areas with no issues. I even have 3 of these in my old golf cart with good results. I picked up 7 of these yesterday. While I was there Luke told me to go down the road bout 3 miles to Interstate distributor and they would buy my group 31 cores for $14 each. So I got 7 free batteries and $28 for gas and lunch. I thought about going back to the truck stop and buying the whole pallet of dead cores and selling them to the distributor as they do for $4 profit on each but I didn`t want to get too greedy and mess up my deal.
| bpimm wrote on Wed, 03 July 2013 12:07 |
I'm working through our new to us 73 26' coach and it has 2 automotive
batteries 1 for the engine and 1 for the house. Who makes a good deep
discharge battery for the house? My Dad has bought several "deep cycle"
batteries for his house boat and they don't seem to be any better than
the typical automotive batteries, they last a couple years then die.
What are the advantages / disadvantages of a single 12v battery vs. 2 6v
batteries in series vs. 2 12v batteries in parallel.
Most of our use will be off grid. Coach has a 4K Onan.
Thanks
Brian
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C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] Battery? [message #213174 is a reply to message #213141] |
Wed, 03 July 2013 14:27 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| bpimm wrote on Wed, 03 July 2013 09:07 |
I'm working through our new to us 73 26' coach and it has 2 automotive
batteries 1 for the engine and 1 for the house. Who makes a good deep
discharge battery for the house? My Dad has bought several "deep cycle"
batteries for his house boat and they don't seem to be any better than
the typical automotive batteries, they last a couple years then die.
What are the advantages / disadvantages of a single 12v battery vs. 2 6v
batteries in series vs. 2 12v batteries in parallel.
Most of our use will be off grid. Coach has a 4K Onan.
Thanks
Brian
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Brian,
As you have a '73 coach, you have to temper some of the advice you receive as the '73 and '74 coaches had some differances. One was how the batteries where set up from the factory. (Keep in mind yours might have been changed by a PO (prior owner).)
The early coaches left the factory with THREE 12 volt batteries.
-- One started the engine and was charged only by the engine alternator.
-- One provided house power and was charged by the engine alternator AND the power converter (AKA: Buzz Box)
Both the above batteries were mounted in the tray under the right front hatch... right over the suspension air tank. With both batteries together up front it was fairly easy to add a "boost" switch/solenoid to connect them together to start the engine even if your engine battery was weak. (Think of it like "self jump starting" a car.)
-- The third battery was mounted back by the Onan. In your 26, it would have been in the same compartment as the Onan, just to the rear of it. (With an early 23 foot coach, the Onan battery access was from INSIDE the coach, next to the wheel well just forward of the Onan.) This Generator starting battery started the generator and nothing else. It was charged ONLY by the generator alternator mounted under the flywheel. (Not the part that provides 120v AC power to your house.) As many early GMC owners hardly ever started the generators, they found the batteries bad when they needed the generator.
During the many changes for the "75 model year, they dropped the separate generator battery, moving the house battery to the rear to provide double duty. (House and generator.) To keep the boost function, they added an additional solenoid and a LONG heavy cable. This complicates the boost system but works MUCH better than the early Battery set-up. If you can "copy" this into your early coach, do so! Just for the house, use a pair of 6v golf cart batteries to get the most bang for your battery dollar.
Your thoughts on 12v 'deep cycle" marine batteries are correct.... they do not last very long when used as deep cycle batteries. This is mostly due to the fact that they are not TRUE deep cycle batteries. They are a compromise between starting and deep cycle and do not due either very well.
Another reason most RV batteries died early (in the past) was the use of old style "dumb" converters... like our buzz boxes. With no smarts built in, it was up to the owner to provide the smarts. That didn't happen very often. 
A good "smart charger" capable converter is a good investment that will pay for itself. (Also saves space as it is must smaller/lighter.)
Anyway, it is past my bed time I have to work tonight... 
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Battery? [message #213177 is a reply to message #213174] |
Wed, 03 July 2013 15:21 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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| Mike Miller wrote on Wed, 03 July 2013 14:27[/quote |
Brian,
As you have a '73 coach, you have to temper some of the advice you receive as the '73 and '74 coaches had some differances. One was how the batteries where set up from the factory. (Keep in mind yours might have been changed by a PO (prior owner).)
The early coaches left the factory with THREE 12 volt batteries.
-- One started the engine and was charged only by the engine alternator.
-- One provided house power and was charged by the engine alternator AND the power converter (AKA: Buzz Box)
Both the above batteries were mounted in the tray under the right front hatch... right over the suspension air tank. With both batteries together up front it was fairly easy to add a "boost" switch/solenoid to connect them together to start the engine even if your engine battery was weak. (Think of it like "self jump starting" a car.)
-- The third battery was mounted back by the Onan. In your 26, it would have been in the same compartment as the Onan, just to the rear of it. (With an early 23 foot coach, the Onan battery access was from INSIDE the coach, next to the wheel well just forward of the Onan.) This Generator starting battery started the generator and nothing else. It was charged ONLY by the generator alternator mounted under the flywheel. (Not the part that provides 120v AC power to your house.) As many early GMC owners hardly ever started the generators, they found the batteries bad when they needed the generator.
During the many changes for the "75 model year, they dropped the separate generator battery, moving the house battery to the rear to provide double duty. (House and generator.) To keep the boost function, they added an additional solenoid and a LONG heavy cable. This complicates the boost system but works MUCH better than the early Battery set-up. If you can "copy" this into your early coach, do so! Just for the house, use a pair of 6v golf cart batteries to get the most bang for your battery dollar.
Your thoughts on 12v 'deep cycle" marine batteries are correct.... they do not last very long when used as deep cycle batteries. This is mostly due to the fact that they are not TRUE deep cycle batteries. They are a compromise between starting and deep cycle and do not due either very well.
Another reason most RV batteries died early (in the past) was the use of old style "dumb" converters... like our buzz boxes. With no smarts built in, it was up to the owner to provide the smarts. That didn't happen very often.
A good "smart charger" capable converter is a good investment that will pay for itself. (Also saves space as it is must smaller/lighter.)
Anyway, it is past my bed time I have to work tonight...
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Mine is a 73 23'. I have toyed with the idea of installing a bigger Onan start battery, a short run of wire(s) to allow me to quickly and easily connect it to/disconnect it from the DC distribution system, and adding a combiner between it and the house battery up front. That would give me the ability to use it as a second house battery, if the one up front runs down. In that scenario, there is no need to worry about paralleling two 12V batteries, I don't need a long run of big wire front to back for the boost function, and the batteries all charge from whatever source is available.
I guess if both batteries up front are dead, and the Onan is the only one charged, I would need to take it out and drag it up front to start the Olds 455.
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| Re: [GMCnet] Battery? [message #213213 is a reply to message #213205] |
Wed, 03 July 2013 19:56 |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Senior Member |
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Oh, dear. This is more involved than I remembered:
<http://www.gmcmhphotos.com/photos/g5425-battery-lift.html>
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
On Jul 3, 2013, at 4:40 PM, Larry Davick wrote:
> That’s right, he crafted something to affix to his floor jack, I think.
>
> As detailed as Ken is, I know it’s documented somewhere.
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] Battery? [message #213230 is a reply to message #213213] |
Wed, 03 July 2013 21:58 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Now, now, no need to panic, Larry. I later needed to R&R a battery on
level ground. It's not documented anywhere, but the "tool" I used is
trivially simple: A 1x8 board is used as a ramp to slide the battery from
the back of the under-hood tray to the suspension's upper A-arm. I cut the
board just long enough to bring the battery into a convenient lifting
position, with the A-arm supporting the weight. I cut the end of the board
toward the front to the angle at which it met the battery tray. A piece of
3/4" aluminum angle screwed to the underside of that end of the board fits
over the flange of the battery tray, securing the ramp in place. Once the
battery's pried up over that flange with a putty knife or similar lever,
it's easy to slide it safely down the ramp to where this old man can still
lift it. Almost as easy to use as the engine hoist adapter you found. :-)
Ken H.
On Jul 3, 2013 5:57 PM, "Larry Davick" <ljdavick@comcast.net> wrote:
> Oh, dear. This is more involved than I remembered:
>
> <http://www.gmcmhphotos.com/photos/g5425-battery-lift.html>
>
>
> Larry Davick
> A Mystery Machine
> 1976(ish) Palm Beach
> Fremont, CA
>
> On Jul 3, 2013, at 4:40 PM, Larry Davick wrote:
>
> > That’s right, he crafted something to affix to his floor jack, I think.
> >
> > As detailed as Ken is, I know it’s documented somewhere.
>
>
> _______________________________________________
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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