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01-26-2009, 04:49 PM
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#1
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Senior Member
Join Date: Jan 2009
Posts: 124
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Hello all, I am new here but I have a question.
I take care of my folks 2007 MADP 4528. Since new I have upgraded almost every aspect of the coach.
Recently my folks were having battery issues. I figured it was too soon to be replacing the house batteries. Turns out only one of the batteries were toast.
After looking over the electrical system I think I have found out why. After speaking to Newmars highline service I found out it is a design flaw (they do not acknowledge it as so).
For the house 12 volt electical system Newmar uses 6 volt batteries wired to produce 12 volts.
They also run a center tap to provide 6 volts for the "low" setting on the interior halogen lighting.
There is a separate 6volt fuse panel located in the middle (2nd) bathroom.
What I found out is Newmar is just pulling raw 6 volts from a single battery without any sort of battery equalizer, or converter invovled. This causes the battery bank to become out of balance. So when the batteries are charged, the one battery is being cooked. This just happens to be the battery that has died.
Ever since the coach was new my old man has dealt with constant boiling over (outgassing) of the wet batteries. It has been a constant pain to keep the batteries and the compartment clean.
After searching this forum I see that boiling over is a common complaint on the high-end DP's. This is definitely can be caused by an out of balance battery bank.
So my question is: Have anyone here come across this 6volt center tap issue? Did you find a solution. I want to solve this before I have them spend the money on new replacement AGM's.
Currently I am looking at equalizers (and converters), but most of them are made for the 24v-12v bus conversion market. Vanner seems to make the best ones ($$$), but so far I have not located a 12v-6v system from a reputable source. Most of them seem to be Chinese ebay specials.
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01-27-2009, 06:07 AM
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#2
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Senior Member
Join Date: Sep 2006
Posts: 1,339
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If you have hi/lo interior light switches you are using 6v to do that. Newmar gets the 6v by "center" tapping the 12v bank wiring and trunking that directly to the bath fuse panel. If I recall, I'll have to check, but I think the banks are cross wired so you are pulling 6v not just from a single battery but from the half bank. You are correct with the Newmar hi/lo configuration.
Either way, I use my 6v lights all the time, boondock all the time (thus fully allowing the "imbalance"), monitor my batteries to a tee, and have had no issues. IMHO, the "imbalance" would seem so slight as to be negligible. In addition, the parasitic effect of a cross-wired multi-battery bank, should essentially "self-equalize" the bank and a low battery in a bank should cause the "other" batteries to cook due to overcharging not the other way around (the low bat causing the charger to see less volts thus causing the charger to overcharge all the batteries except the one needing the charge).
I would verify your charger settings - both battery type and amp settings. Seems to be an overcharging problem driven at the source, not at the batteries. You've got a Magnum in that MA I believe and that should be giving you a safe and proper charge if it is set correctly.
__________________
2007 and 7/8ths Newmar Essex 4502
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01-27-2009, 07:37 AM
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#3
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Senior Member
Join Date: Jul 2006
Location: Pelican Lake Motor Coach Resort, Naples, Florida
Posts: 1,549
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Hi! Great Post. Welcome to the forum. I had a 2007 MADP 4528. We went thru two sets of batteries. Newmar found a few of them with dead cells and said they all had to be repalced. It was done once in Naples, and then we went to the factory a few months later, and they were bad again. The second time we paid Newmar the difference to upgrade them to AGM's. They also added 2 extra as our coach was all electric. They had to put some kind of part, (relay ??) or something in with the AGM's so everything would charge correctly. I wonder now if our batteries died because of your issue. The AGM's worked great and still do as we know the person who purchased our coach. Paul
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2018 King Aire 4553
2018 Cadillac Escalade
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01-27-2009, 03:17 PM
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#4
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Senior Member
Join Date: Jan 2009
Posts: 124
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Thanks for the replies.
RVDude you mentioned you think the batteries are cross wired. I had my old man photograph the battery layout.
I got high-tech with MS paint and created a diagram.
What we found was a bundle of white "mystery" wires. They disappear off under the chassis, so I have no idea where they end up. Do you happen to know what these are for? Is this a separate ground for the 6v system?
Surprisingly Newmar is not as knowledgeable about their electrical systems (among many other thing I have had to repair) as I had hoped.
As for the charge settings, I have replaced the inverter with a better model, I have re-verified all the settings and they are correct.
Jetsmania, do you think the relay was some sort of battery isolation system?
As my folks' coach is a propane version, they do not have the extra batteries installed on the all electric unit.
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01-27-2009, 04:17 PM
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#5
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Senior Member
Join Date: Sep 2006
Posts: 1,339
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Looks like you ARE (as you suspected) pulling 6v from a single battery. You seem to be missing a - to - jumper which if installed would cause the 6v to pull from those 2 batteries in parallel. This would be far more favorable from a loading and "self parasitically equalizing" perspective (I don't mean the charger equalize function for those that might confuse my intent here). A quick fix instead of adding that jumper you could also move the 6v tap to either of the left most - posts (on your diagram) as those batteries are already in a 6v parallel configuration by proper existing jumpers. I had a couple of missing jumpers on my rig that I had Newmar add - which they eagerly did as an acknowledged oversight. BTW I run a propane rig but had the full load of 8 batteries added as a custom - talk about 00 ga jumpers all over the place.
The mystery wires would be 12v. I'll try to look through my stuff to come up with an idea of what they would be. A first guess off the top of my head is they might be trigger wires to the battery boost solenoids.
The relay that jets is talking about is the BIRD (Bi-directional Isolator Relay Delay) setup which routes the alternator/charger to the appropriate bank (chassis/house) first then switches to the other when that primary bank is charged. A good idea since the house and chassis batteries are not matched (e.g. same models). Without it the chargers (alternator/inverter) would both have to see both the house and chassis in parallel in order to charge all. Note that the two battery sets would be load isolated (not charge isolated unless you have the BIRD) through an isolator relay.
Search irv2 (lots of previous posts) and go to http://www.intellitec.com/PDF/5300362.100.pdf to see the manufacturer spec sheet. I would conjecture the absence of a BIRD means the alternator (a less controlled charging device than the inverter) would see both the chassis and house bats as one giant unmatched battery bank to which it delivers the same overall charge and could thus cause the alternator to charge to the weakest battery or the mis-matched internal battery resistances and thus cause an overcharge. Not likely but possible. The inverter being far more sophisticated and having charger time-out profiles programmed in could probably prevent this possible combined battery bank overcharge. Does your dad drive the coach a whole lot?
__________________
2007 and 7/8ths Newmar Essex 4502
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01-27-2009, 04:33 PM
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#6
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Senior Member
Join Date: Jan 2009
Posts: 124
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Where exactly would I need to add a - to - jumper cable?
As for the BIRD, he has that, and it works just peachy.
Before I discovered the 6v lead, I was leaning toward switching to a 12v based battery bank, as the variety of batteries are more numerous. Other than locating 6v from another source do you see any downsides of doing this?
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01-27-2009, 04:42 PM
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#7
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Senior Member
Join Date: Jan 2009
Posts: 124
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After posting the original diagram I realized I missed a 2nd Ground connection.
Here is the updated chart
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01-27-2009, 04:48 PM
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#8
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Senior Member
Join Date: Sep 2006
Posts: 1,339
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You should really check me out on this using a voltmeter (other elec guys please chime in) but I think the missing jumper is on the middle - terminals top to bottom.
As far as I know, there is no other 6v use in the coach so if you don't mind losing the hi/lo lights I see no reason you couldn't swap out to 12v.
However, 6v batteries tend to have better deep cycle capabilities (simplistically due to thicker plates) and another negative is that the more parallel batteries the more the inter-parasitic robbing goes on which thus further reducing battery life. (you'll have 4 12v in parallel instead of only 2 banks of 2 series 6v in parallel - if that makes any sense) In parallel, the batteries will want to "equalize" themselves to a common level thus bleeding off available amp/hrs. Series connections are non-parasitic.
__________________
2007 and 7/8ths Newmar Essex 4502
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01-27-2009, 04:55 PM
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#9
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Senior Member
Join Date: Jan 2009
Posts: 124
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Quote:
Originally posted by RVDude:
change. Are you sure the 6v is actually tapped to the - post as shown?
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Yep, that was the first thing that caught my attention.
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01-27-2009, 05:08 PM
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#10
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Senior Member
Join Date: Sep 2006
Posts: 1,339
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Looking again, that (seeming 6v-) is correct and really delivers 6v+. Follow the current. It goes from the 6v- to the left bank + (which are then paralleled) and when tied to the left bank pair of grounds (I suspected you had 2 chassis grounds they usually do that to ensure a good ground) you have 6v from both the left batteries (I correct my prior single battery 6v supposition and delete my prior move the 6v tap to the left - suggestion). I would still add the - to - jumper to tie the right bank together.
__________________
2007 and 7/8ths Newmar Essex 4502
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01-27-2009, 05:10 PM
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#11
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Senior Member
Newmar Owners Club
Join Date: May 2007
Location: Somewhere....
Posts: 4,054
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Quote:
Originally posted by RVDude:
You should really check me out on this using a voltmeter (other elec guys please chime in) but I think the missing jumper is on the middle - terminals top to bottom. I would move the 6v tap over (verify 6v before you do) as a simpler change. Are you sure the 6v is actually tapped to the - post as shown?
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Adding a jumper there would be redundant. Each of those negative terminals is jumpered to the matching positive on the first bank of batteries, and those positives are jumpered together. So electrically, they're all the same. Your 6 volt lights are pulling from both batteries.
joe
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2008 King Aire 4562, Spartan K3(GT) w/ Cummins ISX 600
2014 Jeep Grand Cherokee Overland 5.7L V8 Hemi w/ Blue Ox Aventa LX Tow Bar and baseplate, SMI Air Force One brake
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01-27-2009, 05:14 PM
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#12
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Senior Member
Newmar Owners Club
Join Date: May 2007
Location: Somewhere....
Posts: 4,054
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Quote:
Originally posted by RVDude:
Looking again, that (seeming 6v-) is correct and really delivers 6v+. Follow the current. It goes from the 6v- to the left bank + (which are then paralleled) and when tied to the left bank pair of grounds (I suspected you had 2 chassis grounds they usually do that to ensure a good ground) you have 6v from both the left batteries (I correct my prior single battery 6v supposition and delete my prior move the 6v tap to the left - suggestion). I would still add the - to - jumper to tie the right bank together.
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I think we posted at about the same time.
Not sure what good adding the other jumper would do. I would be more concerned about issues getting a good connection on those terminals when adding another heavy gauge lug.
joe
__________________
2008 King Aire 4562, Spartan K3(GT) w/ Cummins ISX 600
2014 Jeep Grand Cherokee Overland 5.7L V8 Hemi w/ Blue Ox Aventa LX Tow Bar and baseplate, SMI Air Force One brake
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01-27-2009, 05:16 PM
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#13
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Senior Member
Join Date: Jan 2009
Posts: 124
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Quote:
Originally posted by FlyingDiver:
Your 6 volt lights are pulling from both batteries.
joe
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So are you saying that in the 6v tap is not causing a battery imbalance?
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01-27-2009, 05:20 PM
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#14
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Senior Member
Join Date: Sep 2006
Posts: 1,339
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Quote:
Originally posted by FlyingDiver:
So electrically, they're all the same.
Your 6 volt lights are pulling from both batteries.
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Agreed on both counts.
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2007 and 7/8ths Newmar Essex 4502
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