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Old 11-07-2014, 06:33 PM   #1
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Location: Ottawa, Ontario, Canada
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Battery Charging

Hi everyone.
Newbie here and am puzzled already. I just picked up a new to me 2006 Mandalay 40F. Had it for 3 days now. My problem is before I pick it up the "house" batteries were changed. I have 4 6 volts for the house and 2 12 volts for chassis. After a demonstration from dealer and driving about 2 hours to get to my parking spot we looked at all that we mist while looking to buy. I noticed that the "house" batteries are at 12 volts. I started the engine and had 14.2 on chassis batteries and still 12v on others.
Is there a isolator somewhere, where is it located, are there fuses for this, where. did they maybe forgot to install a wire, I'm sure the engine is suppose to charge these on the run.
Any help to solve the problem would be greatly appreciated.
Thanks so much

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Old 11-07-2014, 09:37 PM   #2
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We don't have a Mandalay, so can offer no advice. But most Class A's do charge the house batteries from the engine. An issue could be as simple as a blown fuse or lose wire on the charge control unit.

Hope someone can offer some advice here.

Best luck

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Old 11-07-2014, 09:39 PM   #3
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Running the engine the alternator will read 14.2 charging. Your house batteries are deep cycle and if they are fully charge they will show 12 Volts. You should get a good battery hydrometer to check your house batteries once and a while. A bad cell can drain the others. New batteries should be check more often because of maybe bad construction. If they are good for 6 months they should be good for years.
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Old 11-08-2014, 04:45 AM   #4
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Welcome to irv2.
Here is info on batteries and every thing else that may be of interest to you.
Enjoy the forums.
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Old 11-08-2014, 08:16 AM   #5
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Your house batteries are deep cycle and if they are fully charge they will show 12 Volts.
Sorry, but I have to strongly disagree with that. House deep cycle batteries will normally show 13.3-13.6 volts when fully charged. 12v represents only about 50% state-of-charge.
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Old 11-08-2014, 09:00 AM   #6
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Call your dealer as something is broken and he needs to fix it...period.

Also note that this is an indication of possible lack of attention to detail.

So other things may be in need of attention.

Search here for checklists and inspection tips and give your unit the "once-over"...twice! Taking notes then have the dealer fix them.

And with the 12 volts have them show you what they found and how it was fixed.

Loose wire or blown fuse are symptoms of other things like no support for wire or possible short.

It is a used unit with a very short warranty and long unknown history...best to find silly things while under the short warranty...
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Old 11-08-2014, 09:26 AM   #7
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While not familiar with your coach, I believe most class A motorhomes should charge the house batteries while running. If your house batteries are 12V with the engine running for a while they are not being charged. They should show charging voltage regardless of state of charge. From there you have to know which system it uses. I agree that if you just got it from a dealer it needs to go back. There is so much information on this site for you to read. Search BIRD or battery or isolator. As to the full charge voltage, moving target, rule of thumb is 2.1V per cell.
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Old 11-08-2014, 09:35 AM   #8
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I believe testing the battery voltage depends on two things.

1. What type of meter/gauge are you reading the voltage on.

2. At what stage of the charging process are you reading the voltage.

12.6 dcv is a full battery. Anything higher is measuring the float charge. Does your meter/gauge read in digital decimals?

12.0 is discharged to 50% of the useable charge.

14.2 dcv on the chassis batteries indicates that the battery charging process was just shut down and the "float" charge is still present. Turn on your headlights for 5 minutes and then test the volts in the chassis battery. A full charge will be @ 12.6 dvc.

BTW on my rig 14.2dcv is the highest charge rate that my alternator should produce. That usually only happens when the battery was low after startup of the engine and still is not fully charged. Normally my alternator charges at 13.6 dcv.

Depending on the answers to the meter and time of measurement, you may not have any problem with your batteries and charging system.
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Old 11-08-2014, 09:43 AM   #9
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This is a very informative site and well worth the read.
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Old 11-08-2014, 09:00 PM   #10
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welcome, and now the fun begins. Any rv that has independent batteries have an isolator. Mine is in the engine compartment. It usually has 4 wires going to it. 1 to the alternator, 1 to coach bat, 1 to starting bat and 1 excite wire. This is used on newer alternators. You can check with a voltmeter. Engine running, blk to ground, and red to each of terminals, should be 14v for alt, and 12.65 for full charge 12v bat. And I think 6.75v for 6 volts. I have 12v deep cycles for my coach.
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Old 11-09-2014, 02:25 AM   #11
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battery charging

Thanks you all for the great info, suggestions and tips.
Yesterday had time to look at all and with tips for this site, I found the "Bird" and started testing all. Found that the purple wire on the "Big Boy" was not making good contact and after this was rectified house battery are charging with Alternator.
The thing I noticed is that soon after starting engine, the solenoid terminals, I have 14.4 volts on one side (chassis post) and the after the bird activates the solenoid I get 13 volts on house side. Guess the "penny" inside the solenoid has corrosion inside and contact is not as should be. Looks like maybe it can be dismantled with the 4 screws at bottom but not sure. Has anyone opened this up to clean the contacts ????
Many thanks again
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Old 11-09-2014, 10:04 AM   #12
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Measure voltage across it.

One lead on each side to see actual voltage drop.

It could be cruddy and may be servicable but others will need to comment there.
Tony & Lori
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Old 11-09-2014, 10:47 AM   #13
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Motorhome 12 volt 1.001.

On most all (if not all) motor homes there is an isolator device, these come in two or 3 flavors.

One kind is controlled by the ignition switch, When you start your engine, it engages, it may take a few seconds to engage (Time delay) or it may engage right away.

The next is voltage controlled. It will not engage till the engine battery comes up to around 13 volts, NOTE: your dash voltmeter may show a higher voltage than the engine voltage. (Line loss in the wires) so it may take like 10-20 minutes for this one to engage if the engine battery is low enough.

The thired is the BIRD (Bidirectional Isolator Relay Device) IF EITHER house OR chassis goes over 13 volts, it engages (This one is best of course)

I suspect, in your case, the isolator may not be closing, this could be due to a blown/missing fuse, or a bad isolator relay or a control system problem, Step one is locating the solenoid. (Relay).
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Old 11-09-2014, 11:42 AM   #14
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Welcome, to the forum and good luck with your Mandalay. All the previous post's have pretty much said it all.


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