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Old 05-25-2016, 06:19 PM   #1
Join Date: Jan 2016
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Adding a gen battery

I have a 2007 Camelot. The four 6volt batteries doesn't turn the generator over very fast. Most the time I have to hit the boost switch to start it. I'm wanting to add a 12volt battery by the generator on the slide out. Does anyone else have this trouble. I have checked all the connections.
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Old 05-25-2016, 06:35 PM   #2
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Are the four 6 volt batteries in good condition? If the batteries are ok, and the connections are good, then adding another battery logically should not make s difference. But if using the boost switch works it is not a problem with the generator itself. Hmmm...
Vince and Susan
2011 Tiffin Phaeton 40QTH (Cummins ISC/Freightliner)
Flat towing a modified 2005 Jeep (Rubicon Wrangler)
Previously a 2002 Fleetwood Pace Arrow 37A and a 1995 Safari Trek 2830.
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Old 05-25-2016, 06:48 PM   #3
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Agree, if four 6-volt batteries aren't turning over your genset very well, think you have other issues--think I'd get the bats load tested. Some rigs have genset start circuit connected the chassis bat, others are connected to the house bats. Either way, something is wrong.....need to isolate root cause before investing in yet another battery that you will have to carry.....
Old Scout
2003 Alpine 40' MDTS
New Braunfels, Texas
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Old 05-25-2016, 06:54 PM   #4
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Is this a new issue or a long standing problem.

4 series, parallel 6 volt batteries should crank almost any generator.

Since the boost switch makes it crank well, I would look real hard at the 6 volt banks, ground connection.

The ground for the lights, fridge and most other house components, use a light, 6 or 8 gauge, negative wire to the fuse area.

The generator ground wire goes to the chassis and so should a large house bank ground cable.

When you hit the boost, you are using the well grounded, start battery.

Just a theory but check it out.
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Old 05-25-2016, 07:16 PM   #5
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I agree with some of the comments above; somethin is wrong with your house batteries or the circuit to the gen starter.
If you add a separate battery then you also need to add some sort of charging circuit to keep it charged and you will still have a problem with the house batteries that my have other problems that just haven't shown up yet.
Paul, Kathy, and Tux the Mini Schnauzer
2014 Tiffin Phaeton 42 LH, 2013 Honda CRV
"When the time comes to look back, make sure you'll like what you see"
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Old 05-25-2016, 07:31 PM   #6
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Thanks for the replies. Looks like in need to dig deeper into this issue. I've owned this motor home for 8 months. Batteries we less than 2 months old when I ought it. I had them tested and checked good.
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Old 05-25-2016, 07:39 PM   #7
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A little more thinking. Take a set of jumper cables and using only the black ends, clamp one end to the neg. post, on the house bank and clamp the other to a clean part of the chassis.

See if it makes a difference.
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Old 05-26-2016, 09:51 AM   #8
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Your best friend on a mh is a DVOM, start here
Connect vdom to generator battery ground lug on back of genset,connect other end of dvom to a good chassis (frame) ground,set dvom for 12v dc crank genset and see how many volts you have on dvom,should be less than .8 volts.
If voltage is less than .8v do the same test on the positive lug to the FRB terminal for house battery.
I bet you will find your problem.
My theory is, "it worked when new" dont re invent the wheel.

Retired ford field service engineer
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Old 05-26-2016, 05:22 PM   #9
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I have the same issue with my 2005 Imperial. About 50% of the time I need to use the boost to get it started. When it cranks, it seems to only "half crank".

I cleaned all connections and had the relatively new batteries tested. They checked out okay as well.

Some have suggested that HR used battery cables that were too small gauge to run from the batteries to the generator causing it to not have enough voltage to start it.

I too was looking into the idea of installing a separate battery up front to help.

Now recently I had a complete service of the generator (oil, filter, fuel filter, air filter and new coolant) and the few times I started it since, the generator seemed to start fine. I only had a few chances to try it since then so I don't know if that helped or it was just a fluke.
Mike and Lisa
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Old 06-01-2016, 06:49 PM   #10
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I had the exact same issue and fought it for over two years. I couldn't boondock because I was never sure if my generator would start. Sometimes, not even hitting the boost button would get the dang thing started. My first step was to replace the batteries but that wasn't the answer. I then took it to an authorized Onan service center. They began troubleshooting the issue and quickly found that there was 12+ volts at the generator terminal. But once they tried to start the generator, the voltage dropped to 7.5 volts. They cleaned all the terminals they could get to with no luck. They stopped working on it when they discovered a black widow spider in the cable tunnel. (I guess mid-westerners aren't used to black widows)

I continued to try things like replacing disconnect switches and more cleaning of connections to no avail. Some people claim there is a connector or splice somewhere on the main cable in the cable run to the front of the coach that could be corroded. I can't attest to that.

I then saw the solution right here on this forum. Someone (Sorry, I can't remember who) installed a battery at the front of the coach and used an Amp-L-Start to keep it charged. This lead me to believe that others have experienced the same problem and it wasn't just my coach. I decided to go that route and haven't regretted it. I just copied the idea and pics are below.

When we began to design this install, my friend (who is the craftsman of this venture) said we should check to see what size battery to use. I was thinking along the line of a motorcycle battery but a quick check of the Onan installation manual showed that we needed a minimum of 475 Cold Cranking Amps (CCA). They actually recommend a 650 CCA battery for really cold weather starts, which meant a car battery .

The most shocking thing I found in the installation manual was the cable length recommendation. For 3/0 cable the maximum cable length from the battery to the generator is 20 ft. They allow a max of 25 ft. if you have 1200 CCA batteries. Well, on my coach the cable, which appears to be 3/0 at most, goes from the battery compartment to the rear of the coach to the disconnect switches. From there it goes to the front of the coach. That is well over 45 ft. of cable. Having worked in the design and construction of electric power systems, I have a fair understanding of how voltage drops along a length of wire as the amperage goes up. So, to eliminate that voltage drop issue, I just moved the battery next to the generator. It made sense to me.

Now, my generator cranks fast and starts right up. It was one of the best mods I have made to the coach.
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Richard and Laura Mae
2007 Monaco Camelot/2003 Jeep Rubicon or 2006 Jeep Commander
From the Land of Enchantment, New Mexico
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Old 06-01-2016, 07:22 PM   #11
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Thanks for the post. I have checked everything. I am going to do the same install you did.
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Old 06-01-2016, 08:01 PM   #12
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Thanks for the post and pictures. Couple questions: Are the coach batteries still used as well or is this the only battery? If so I assume the boost function is no longer possible, correct?
Mike and Lisa
2005 HR Imperial 42 DSQ
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Old 06-01-2016, 08:09 PM   #13
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Well the Signature must be setup differently. I am pretty sure that my generator uses the chassis batteries to start. The logic is that if you are dry camping and run your house batteries down then you can't start the generator with the house batteries so therefore the generator starts off the chassis batteries
Mike Canter
"Gunner" USN Retired, Airdale
2004 Monaco Signature 44' Conquest. Detroit 60
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Old 06-01-2016, 08:39 PM   #14
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Mike, That makes sense but this winter my chassis batteries went dead and I couldn't start the engine. I was able to start the generator though. I just assumed the house batteries started the generator.
Mike and Lisa
2005 HR Imperial 42 DSQ
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