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Old 06-24-2015, 12:21 PM   #1
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Jumpstarting Motorhome when Chassis and Coach Batteries are dead

Our Berkshire 34QS was in storage for 4 or 5 weeks and not connected to shore power. I went to start it, in order to take it in for warranty service, and all 6 batteries were dead. The 12v batteries were at about 4 or 5 volts and the 6 volt batteries were about half that. I've got a Honda Civic with a pretty small battery and devised the following scheme to get the RV Cummins engine started.

Charging the 4 house batteries to the point of getting the Onan generator started seemed a bit time consuming (I think the Honda alternator puts out over 100 amps, though), so I though of splitting them in two to only have to charge half of them. Then I thought a little more and figured out how to jumpstart the Onan from the car without any batteries attached.

It turns out that the house batteries are in pairs to give 12 volts, with one pair towards the front of the coach and the other towards the back. The pairs are in parallel, but the back pair goes to the Magnum power unit, so I assumed that the connections off of the front pair go to the Onan. I disconnected the positive terminal so that no batteries were hooked up to the Onan, and jumpstarted from my car battery to this wire (not the battery). That got the Onan going, but it seemed to want to have a battery connected – otherwise it would turn off. So, I slipped the terminal spade back onto the battery while the alligator from the jumper was attached. Held it down and unclipped the jumper cable. Then I put on the wire to the rear battery set and bolted it all up. The Magnum power centre said I was charging at about 70 amps, so I ran this for a while and then ran the emergency start to get the Cummins engine started. I drove with the Onan and the Cummins both working, to avoid stalling the Cummins – maybe too paranoic.

NOTE, if you do this, you are playing with hot 12 volt lines, both at the batteries and the jumper, so be careful to keep the wrench away from ground and to keep the jumper cable away from chassis ground.

Is there an official way to do this? It would be nice if I could directly jump to the Onan generator and just turn off the battery switch in the battery compartment. But, I didn't know where the 12v connects to the Onan. I didn't remove any of the inspection panels, perhaps being too hasty.

The other question is why did all 6 batteries die together within 5 weeks of being fully charged? I had the "salesman" switch at the front of the coach turned off and the headlights were off. So, this leads me to suspect that the dealer let the batteries freeze over the winter. I took delivery on May 9, and the dealer was going to great lengths to charge the batteries when I picked it up.

–Gordon
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Old 06-24-2015, 12:27 PM   #2
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Gordon,
If the dealer was 'going to great lengths to charge the batteries' then there must have been a problem with the batteries. Since you have 34QS I am assuming that it is a 2014 or 2015 model year. I would think that the batteries should keep a charge for more than 5 weeks. I would have the batteries tested and see what that shows.
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Old 06-24-2015, 12:35 PM   #3
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Tom,
Thanks. I did take it in for a bunch of warranty items, and have told them that the batteries were dead. Unfortunately, they have an incentive to stonewall me, since are likely responsible for the dead batteries if they did freeze. They probably can't pass that on to FR.

I'll see what happens. It is the first time I've had it in for warranty service, so I should be patient and see what the dealer does. I'll let you know the outcome.

–Gordon
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Old 06-24-2015, 02:13 PM   #4
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If all you did was to turn off the "salesman" switch at the front of the coach you have quite a large parasitic draw on the batteries. To be sure you completely turn off everything you must turn off the house battery and coach battery switches located in the compartment where all the batteries are located. That should allow the coach be stored for several weeks/months without any issues.


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Old 06-24-2015, 02:16 PM   #5
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If all you did was to turn off the "salesman" switch at the front of the coach you have quite a large parasitic draw on the batteries. To be sure you completely turn off everything you must turn off the house battery and coach battery switches located in the compartment where all the batteries are located. That should allow the coach be stored for several weeks/months without any issues.


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Also found out the hard way, inverter must be turned off, even with battery compartment switches off.



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Old 06-24-2015, 02:28 PM   #6
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Originally Posted by gordonsick View Post

It turns out that the house batteries are in pairs to give 12 volts, with one pair towards the front of the coach and the other towards the back. The pairs are in parallel, but the back pair goes to the Magnum power unit, so I assumed that the connections off of the front pair go to the Onan.
Gordon, if in fact only one pair of 6 volt batteries are connected to the Magnum, you might want to have the dealer check the wiring. I believe the Magnum should be powered by all four batteries to get the maximum usage time.

Here is the typical wiring for four 6 volt batteries. Notice the pairs are in series to get 12 volts, them paralleled out to the coach at one 12 volt point.

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Old 06-24-2015, 06:09 PM   #7
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Gordon, if in fact only one pair of 6 volt batteries are connected to the Magnum, you might want to have the dealer check the wiring. I believe the Magnum should be powered by all four batteries to get the maximum usage time.

Here is the typical wiring for four 6 volt batteries. Notice the pairs are in series to get 12 volts, them paralleled out to the coach at one 12 volt point.

Dan,
My batteries are hooked in the series-parallel configuration that is electrically identical to your diagram.

My point was that the setup physically has a bus that connects the two sets of 12v battery pairs (note that a battery of batteries is technically still a battery – it just has more cells). The negative sides all go to ground. But, one end of the positive bus is physically connected to the Magnum (at the back end) and the other end is physically connected to the Onan generator.

If the bus is not broken, then the Onan is electrically connected to the Magnum, which is connected to the two 12v pairs on the positive side.

What I did was to break the bus at the physical end that goes to the Onan by unbolting that battery terminal. This let me jump start the Onan without the drag of having to charge the house batteries. Then, I hooked up the the house batteries by rejoining the bus.
–Gordon
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Old 06-24-2015, 06:16 PM   #8
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If all you did was to turn off the "salesman" switch at the front of the coach you have quite a large parasitic draw on the batteries. To be sure you completely turn off everything you must turn off the house battery and coach battery switches located in the compartment where all the batteries are located. That should allow the coach be stored for several weeks/months without any issues.


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That is quite a strong statement.

Can you quantify the amount of draw on the chassis batteries? I can park my car for months without killing the batteries, and that should be comparable to the draw on the chassis batteries, relative to size. Is it normal for chassis batteries to die after 5 weeks?

What is the source of parasitic draw on the house batteries if the salesman switch is off? I understand that the residential fridge can draw, but we had the fridge turned off.

I'm curious to see whether other forum members always turn off both kill switches in their battery compartments if they are going to park the RV for a month in the summer when not on shore power.
–Gordon
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Old 06-24-2015, 06:42 PM   #9
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If I am going to park it without power, I for one do turn off both cutoffs in the battery compartments. Not just the salesman switch.


Marty's statement may have sounded strong. I think the point is that on our MHs it is hard to tell what all may be drawing power without the battery cutoff switches turned off in the battery bays.
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Old 06-24-2015, 06:50 PM   #10
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For one thing that continually draws power is the combination propane/CO detector which also controlls the safety valve on the propane tank. There may be others on each individual coaches.


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Old 06-24-2015, 07:02 PM   #11
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I always disconnect when storing for long periods. Store button is ok for a week or so but I have better luck leaving my store button on and disconnect from the main in the battery compartment. When I return I turn the main disconnect to on and I start my genset and my engine, it works for me. I always at least once a month will run my genset and engine for a hour or more since I have limited electricity access. When I can get my turn to the electricity in the storage facility I will run my 100ft extension cord and charge for 8 or more hours. I have had battery issues from day one very similar to yours and now after a couple of years I have a system and its working.
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Old 06-24-2015, 09:07 PM   #12
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As mentioned, you also need to turn off the inverter! When it is on, it is "seeking" a signal. I found this true, when dry camping, having turned off all power at night, I found my battery had expended power during the night. I eventually turned off the inverter at night, and then found very little if any expended power from the batteries the next morning.


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Old 06-24-2015, 09:32 PM   #13
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I also turn off the battery disconnects when storing for more than a week. I turn off both but I am surprised that your chassis battery's were dead after only a month. I could not tell you all the draws but I'm sure it is more than a car and I'm sure it has the disconnects for a reason. I use them. I would have them tested but in my experience if they froze the case is generally budge out. Run your hand down the side to see if the case is square. Not always but it's a good indication. Good luck.



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Old 06-25-2015, 12:57 PM   #14
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Maybe the batteries were never fully charged by the dealer and that is why they die off so quickly. Especially if they had them hooked up to a charger with a fast charge prior to delivery. Un-plug your shore power and hook up a good battery charger and either slow charge overnight for a day or so or fast charge for a good 4-5 hours. Like baking, test to see if done!
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Old 06-25-2015, 01:35 PM   #15
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Maybe the batteries were never fully charged by the dealer and that is why they die off so quickly. ...
The batteries were fully charged, because the remote Magnum unit had reported that they were fully charged and that it was just doing the float charge or whatever.
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Old 06-25-2015, 01:41 PM   #16
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I also turn off the battery disconnects when storing for more than a week. I turn off both but I am surprised that your chassis battery's were dead after only a month. .... I use them. I would have them tested but in my experience if they froze the case is generally budge out. Run your hand down the side to see if the case is square. Not always but it's a good indication. Good luck.
Phil,
I agree that the fact that the chassis batteries went down is harder to explain.

I did look for obvious damage of a freeze, like a bulge or leaking crack and found none. But, I didn't look too hard. I also never checked the water in the batteries.

If the Dealer does nothing for warranty, I'll do these more careful checks.

Given what everyone is saying, it looks like I need to disconnect the batteries if I store it. I wonder how many settings I'll lose in all the electronic devices.
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Old 06-25-2015, 01:43 PM   #17
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Easiest way to tell is with a clamp meter. Clamp it around the main red batt wire with the salesman switch turned off and you'll know exactly what your parasitic amp drain is. The you can pull fuses or clamp directly connected wires to see what the parasitic drains are. Alternatively...if you're not curious...just disconnect the negative wire when in storage (and after charging to 100%) and your batts should be good for 2-3 months minimum even to 50% charge.

You have over 400 amp hours of battery bank with the 4 6V's . A .5 amp parasitic draw would flatten them in 5 weeks even if in like new condition... but a .5 amp draw is way more than just a propane detector. If the clamp measurement doesn't show close to that kind of draw...I'd bet on murdered batteries and would NOT blame the dealer unless they were told to charge them and they actually froze and you can see case deformation or cracking. . BATTERIES that are charged don't freeze...discharged ones do. Abuse in charging /discharging regimens...cooking batteries by leaving on full time charging...and failure to keep the water up are the main ways batteries lose capacity and fail. But something like a Magnum on standby and not wired through the cutoff switch can kill a set quickly too.
If you don't have a clamp meter that can read DC amps...they are very handed to have and start at about 50 bucks on Amazon. I have this one and am very happy with it. Amazon.com: Auto ranging AC/DC Digital Clamp Meter: Home Improvement
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Old 06-25-2015, 05:21 PM   #18
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Just a suggestion. If you have a power source, when I store mine, I use battery tenders and I've had no problems (except when I left my inverter on.
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Old 06-25-2015, 05:39 PM   #19
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Just a suggestion. If you have a power source, when I store mine, I use battery tenders and I've had no problems (except when I left my inverter on.
Gasman,
I agree that having a power source would solve all of these problems. But, I'm storing it in a large storage area with hundreds of RVs that have no power. That is the way almost everyone does it in Calgary.

I'm hoping to do some work in my back yard to make room for the RV. Most people don't have a big enough yard, but a little work to take out a hill will give me room. But, that is a project for next year. Right now, I have a trailer in that spot and it is always on shore power.
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Old 06-25-2015, 05:53 PM   #20
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Easiest way to tell is with a clamp meter. Clamp it around the main red batt wire with the salesman switch turned off and you'll know exactly what your parasitic amp drain is. The you can pull fuses or clamp directly connected wires to see what the parasitic drains are. Alternatively...if you're not curious...just disconnect the negative wire when in storage (and after charging to 100%) and your batts should be good for 2-3 months minimum even to 50% charge.

You have over 400 amp hours of battery bank with the 4 6V's . A .5 amp parasitic draw would flatten them in 5 weeks even if in like new condition... but a .5 amp draw is way more than just a propane detector. If the clamp measurement doesn't show close to that kind of draw...I'd bet on murdered batteries and would NOT blame the dealer unless they were told to charge them and they actually froze and you can see case deformation or cracking. . BATTERIES that are charged don't freeze...discharged ones do. Abuse in charging /discharging regimens...cooking batteries by leaving on full time charging...and failure to keep the water up are the main ways batteries lose capacity and fail. But something like a Magnum on standby and not wired through the cutoff switch can kill a set quickly too.
If you don't have a clamp meter that can read DC amps...they are very handed to have and start at about 50 bucks on Amazon. I have this one and am very happy with it. Amazon.com: Auto ranging AC/DC Digital Clamp Meter: Home Improvement
Cam,
I agree that a Clamp Meter would be handy. I used one a few decades ago and would have to buy one now. My Dad had access to one a long time ago.

Your point that a 0.5 amp draw would kill the house batteries in a week or so is very useful. I didn't know how few amp hours I have in those house batteries. I can imagine there are several components in the RV that might come up to more than the 0.5 amps.

In terms of blame if the batteries were actually frozen, that is an interesting question of responsibility. The dealer put the new RV into inventory in November and drove it to an RV show in January where we executed the purchase. One of the terms of purchase was that they would store until Spring, giving me time to arrange storage and get an airbrake licence. They did winterize it, so they clearly know about the importance of keeping batteries up. It is not obvious to me that I had the responsibility of actually telling them to keep the batteries charged – they had a whole lot full of RVs and should be experienced in taking care of the batteries.

Overall, it may well be that they weren't frozen over the winter. I'm still a little surprised that the chassis batteries died, because I can't see what would draw on them if the lights are off.

I'll wait to see the results when I pick it up after the warranty work is finished. And, clearly, I do need to use the cutoff switches when I store it.

Thanks to all for your advice.
–cheers, Gordon
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