| [GMCnet] Grounding [message #213088] |
Tue, 02 July 2013 21:39  |
Anonymous
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I have been chasing the 12V house system today and there are to many
things acting weird so I know it's a ground issue I was chasing ground
loops when I found Saturday's post on grounding the house and chassis,
Thank you Ken for that nice grounding presentation. As my coach sits now
the Engine battery is grounded to the engine block as it should be, My
house battery is located with the engine battery and is grounded to the
radiator support. I put it up on ramps and there is no braided strap at
the back of the engine that I can see so I need to add that one and I'll
replace the one from the body to the chassis at the battery tray in the
right front as well. Now you show 2 braided straps one RF and 1 LR plus
I thought I read that there is an extra if there is a generator so is
that 2 in the LR with a Generator , or just 1 in the LR with a generator
and none with out? Mine has a 4K Onan and I can only see a ground point
to the generator tray, is that correct? there is also a location for a
battery next to the generator, is that the location for the house
battery or does the generator get it's own battery?
Thanks for any insights,
Brian
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| Re: [GMCnet] Grounding [message #213098 is a reply to message #213088] |
Tue, 02 July 2013 23:41  |
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Anonymous
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Sorry, 73 26' I can't post on the forum so no sig block until I get
activated. So the rear battery is for the Generator on the 73. I haven't
gone through the Generator yet but I did hit the start switch on the
panel inside and the solenoid clicked so it has some power from the
house or engine battery. Were the early ones completely separate? off to
the schematics.
Brian
Early models had a dedicated battery to start the Onan, later models
used the house battery to start the Onan.
It would help if you would include some info about your GMC in your
signature block.
'73 23' Sequoia For Camping
'73 23' CanyonLands For Sale
UA (Upper Alabama)
"Time is money. If you use YOUR time, you get to keep YOUR money."
-------- Original Message --------
Subject: Grounding
From: <brian@pimmlabs.com>
Date: Tue, July 02, 2013 7:39 pm
To: gmclist@temp.gmcnet.org
I have been chasing the 12V house system today and there are to many
things acting weird so I know it's a ground issue I was chasing ground
loops when I found Saturday's post on grounding the house and chassis,
Thank you Ken for that nice grounding presentation. As my coach sits now
the Engine battery is grounded to the engine block as it should be, My
house battery is located with the engine battery and is grounded to the
radiator support. I put it up on ramps and there is no braided strap at
the back of the engine that I can see so I need to add that one and I'll
replace the one from the body to the chassis at the battery tray in the
right front as well. Now you show 2 braided straps one RF and 1 LR plus
I thought I read that there is an extra if there is a generator so is
that 2 in the LR with a Generator , or just 1 in the LR with a generator
and none with out? Mine has a 4K Onan and I can only see a ground point
to the generator tray, is that correct? there is also a location for a
battery next to the generator, is that the location for the house
battery or does the generator get it's own battery?
Thanks for any insights,
Brian
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| Re: [GMCnet] Grounding [message #213111 is a reply to message #213098] |
Wed, 03 July 2013 03:18 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Early GMC Onan generators had a stand alone starting battery. The starting battery gets hooked directly to the Onan. It never posers anything other than the starter.
I'm not sure where the negative (ground) cable is normally attached on that stand alone starting battery. I would assume anywhere on the engine would do. I know the positive cable goes to the starter solenoid. I have only once ever worked on an early GMC with a separate starting battery for the Onan, so my experience with that arrangement is very limited.
On your ground strap question. There is one strap from the body to the frame and it is located over the right front wheel. There is a second on from the back of the transmission to the frame.
The optional 3rd one is the one in the left rear near the Onan. No Onan, no 3rd strap.
A few GMCs came with a different generator. I have no idea if those other generator installations also included the installation of the 3rd strap.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Grounding [message #213138 is a reply to message #213088] |
Wed, 03 July 2013 10:59 |
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Anonymous
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Thanks Ken, I will restore the factory grounding and see where the PO
tied the generator battery in with the house battery. Is there a reason
to keep the house and generator start separate? It seems at first glance
like it would double your house battery capacity and the boost function
should work both ways if you ran the house down to far to start the
Generator.
Brian
Early GMC Onan generators had a stand alone starting battery. The
starting battery gets hooked directly to the Onan. It never posers
anything other than the starter.
I'm not sure where the negative (ground) cable is normally attached on
that stand alone starting battery. I would assume anywhere on the engine
would do. I know the positive cable goes to the starter solenoid. I have
only once ever worked on an early GMC with a separate starting battery
for the Onan, so my experience with that arrangement is very limited.
On your ground strap question. There is one strap from the body to the
frame and it is located over the right front wheel. There is a second on
from the back of the transmission to the frame.
The optional 3rd one is the one in the left rear near the Onan. No Onan,
no 3rd strap.
A few GMCs came with a different generator. I have no idea if those
other generator installations also included the installation of the 3rd
strap.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Grounding [message #213216 is a reply to message #213138] |
Wed, 03 July 2013 20:05 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| bpimm wrote on Wed, 03 July 2013 11:59 |
Thanks Ken, I will restore the factory grounding and see where the PO tied the generator battery in with the house battery. Is there a reason to keep the house and generator start separate? It seems at first glance like it would double your house battery capacity and the boost function should work both ways if you ran the house down to far to start the Generator.
Brian
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Brian,
Lead acid batteries never play well together. If you put a battery by the genset(APU) and parallel it with the house bank, you will get a marginal and unreliable increase in the bank capacity. If you want them to truly add, then the batteries have to be identical (consecutive serial numbers is OK) and the cables have to be perfectly matched. The return on this investment is just not good.
Either decide that you are going to start the APU on the house bank - Many people do, or you will have a dedicated battery for it. I like the later because I always run the edges of the envelope (remember I have put 53 gallons on a few times). So, I could kill the main engine battery and the house bank and still be able to spin the APU enough to light it. I have not yet had to do this, but I find it comforting that the capability is there.
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: [GMCnet] Grounding [message #213224 is a reply to message #213216] |
Wed, 03 July 2013 21:35 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I would not parallel the generator start battery and the house batteries. If you run down the house batteries you also will run done the generator start battery. That is not the end of the world because you could always hit the boost switch on the dash and start the Onan off of the engine battery. If you are doing this generator boost start, I would start the main engine first so the engine driven alternator is running while boost starting.
The second reason I would do not this is placing batteries in parallel frequently causes the batteries to self discharge into each other. The end result is you have less total battery storage capacity than you would with them separated.
Now if you want to charge the engine starting battery from the house system and engine driven alternator, look at installing an optional combiner between the two batteries. A combiner functions somewhat like the isolator up front for charging two batteries while keeping them separated. The combiner also does not have the .7 volt drop across it like an isolator does.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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