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Old 08-01-2018, 08:27 PM   #1
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Battery Bay wiring question

I have an issue with my coach batteries losing charge while stationary. I believe our inverter / charger should be able to maintain and float charge the coach and house battery banks. In the attached photo, you can see two wires attached to the positive bar across the coach batteries. I tested, and there are only 10.5 volts across the two wires, and it doesn't make sense to me that both would be connected to the positive post.

Any thoughts are greatly appreciated.

Dennis and Jennifer Hershey
The Houseless Hershey's
2014 Thor Palazzo 33.3 with
2012 Buick Enclave toadClick image for larger version

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Old 08-01-2018, 08:47 PM   #2
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only charges house batteries

Your inverter/charger most likely only charges the house batteries which are isolated from the chassis batteries. The two wires you see are for chassis components ECM (engine control module) etc....
My coach came with a 10 watt solar panel to trickle charge the chassis batteries. It also came with and after market Trick-L-start, a unit that will charge off the house batteries.

Ultra TRIK-L-START Starting Battery Charger/Maintainer

Just curious how long does the coach have to sit to get down to 10.5 volts, you may have a ghost parasitic draw that may need to be diagnosed. Hope this helps.
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Old 08-01-2018, 11:33 PM   #3
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Quote:
Originally Posted by dhershey View Post
I have an issue with my coach batteries losing charge while stationary. I believe our inverter / charger should be able to maintain and float charge the coach and house battery banks. In the attached photo, you can see two wires attached to the positive bar across the coach batteries. I tested, and there are only 10.5 volts across the two wires, and it doesn't make sense to me that both would be connected to the positive post.

Any thoughts are greatly appreciated.

Dennis and Jennifer Hershey
The Houseless Hershey's
2014 Thor Palazzo 33.3 with
2012 Buick Enclave toadAttachment 213538

RV wiring is as complex as any vehicle short of an aircraft. Personally, I objected to devoting half my battery space/capacity to starting, an intermittent activity that takes a few seconds to accomplish, so I used a 4 gauge wire to bridge the two banks making one bigger well. It doesn't make sense for both charger wires to go to one battery bank - you say it's the house bank, not the engine, yet the house bank is losing charge (not being floated by the charger inverter). Your VOM could be inaccurate, by the way - check the voltage with a second meter to be sure. I would suggest this is an instance when a professional RV electrician should be engaged to get your wiring straightened out and properly tested - I don't think you will solve this with chatter on line. Peter
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Old 08-02-2018, 05:26 AM   #4
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Many MHs have 2 pos leads on both engine and house battys.
Usually one can be disconnected and the other us always on for key components... starter, ECM, safety detectors, etc.
10.5 us very low V...
Check water
Batty age? Orig equip maybe dead
If this is a new problem... worked OK previously and not now...
Start by removing batty charging and have it load tested. Take pics and label all wires when disconnecting.
On some house & engine systems it is important which terminal to remove first to prevent damage. Best to read manuals and confirm w mfg to avoid damage.
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Old 08-02-2018, 08:40 AM   #5
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Hard to diagnose your particular situation from information you provided.

However, the charger should be connected to the house batteries. The chassis batteries are charged through the Trombetta relay which is controlled by the Bird relay. It works in reverse during driving while alternator is running the house batteries are charged through the same system.

10.5 volts is DEAD. Batteries are probably damaged at this point. Would need to check fluids, charge, check specific gravity, then load test to determine. Batteries should not be discharged more than 50% (about 11.9 volts) before charging.

If you do not have basic battery knowledge or electrical wiring knowledge recommend taking to professional.

FWIW
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Old 08-02-2018, 08:42 AM   #6
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Sorry - forgot to mention second line is the one that connects the banks together through the Trombetta relay
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Old 08-02-2018, 10:47 AM   #7
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Hi Dennis! Welcome to IRV2! We're sure glad you joined the gang!

Sorry I can't help with that.

Good luck, happy trails, and God bless!
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Old 08-02-2018, 09:39 PM   #8
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Quote:
Originally Posted by cptdzl View Post
Your inverter/charger most likely only charges the house batteries which are isolated from the chassis batteries. The two wires you see are for chassis components ECM (engine control module) etc....
My coach came with a 10 watt solar panel to trickle charge the chassis batteries. It also came with and after market Trick-L-start, a unit that will charge off the house batteries.

Ultra TRIK-L-START Starting Battery Charger/Maintainer

Just curious how long does the coach have to sit to get down to 10.5 volts, you may have a ghost parasitic draw that may need to be diagnosed. Hope this helps.
Helps a lot, thanks. I've put a trickle charger on the coach batteries temporarily. Going to order the charger you mentioned for the long haul.

Just to clarify, the 10.5 volts was on the two "extra" wires coming in. My coach batteries were at 12.4 volts. I guess that is considered low voltage.

When I was sitting for the prolonged period, they dropped below 9 volts. Not going to let that happen again.

House batteries are good, water level is fine, spare distilled water is riding in the storage bay just in case.
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Old 08-03-2018, 07:52 AM   #9
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Helps a lot, thanks. I've put a trickle charger on the coach batteries temporarily. Going to order the charger you mentioned for the long haul.

Just to clarify, the 10.5 volts was on the two "extra" wires coming in. My coach batteries were at 12.4 volts. I guess that is considered low voltage.

When I was sitting for the prolonged period, they dropped below 9 volts. Not going to let that happen again.

House batteries are good, water level is fine, spare distilled water is riding in the storage bay just in case.

The actual voltages for 12 volt batteries, or pairs of 6 volt batteries in series (usually golf cart batteries) are as follows with no load and no charge coming in: 12.8 is fully charged. 12.2 is 50% discharged. You should endeavor to NEVER let the voltage drop below 12.0. When the voltage is low, the starter motor draws a LOT of extra current and low voltage is the usuall cause of burning out a starter. One idea is once you've gotten things straightened out is to add solar panel(s) so that you are always adding to the batteries whether it is sitting, running, or plugged in. I found that solar can burn out an alternator stator when the two are both supplying current to the batteries, so I always disconnect the solar panels when underway. One beauty is that if you run your batteries down overnight, when the sun comes out you will soon have enough to start the genset which will quickly supply enough charge to start the main engine. Peter
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Old 08-03-2018, 01:20 PM   #10
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Quote:
Originally Posted by dhershey View Post
I have an issue with my coach batteries losing charge while stationary. I believe our inverter / charger should be able to maintain and float charge the coach and house battery banks. In the attached photo, you can see two wires attached to the positive bar across the coach batteries. I tested, and there are only 10.5 volts across the two wires, and it doesn't make sense to me that both would be connected to the positive post.

Any thoughts are greatly appreciated.

Dennis and Jennifer Hershey
The Houseless Hershey's
2014 Thor Palazzo 33.3 with
2012 Buick Enclave toadAttachment 213538
Quote:
Originally Posted by dhershey View Post
Helps a lot, thanks. I've put a trickle charger on the coach batteries temporarily. Going to order the charger you mentioned for the long haul.

Just to clarify, the 10.5 volts was on the two "extra" wires coming in. My coach batteries were at 12.4 volts. I guess that is considered low voltage.

When I was sitting for the prolonged period, they dropped below 9 volts. Not going to let that happen again.

House batteries are good, water level is fine, spare distilled water is riding in the storage bay just in case.
Dennis,
There's a couple of items I'd like to clarify before I maybe give you the wrong ideas or suggestions here. One, in your original post, you stated that: you "believe that the inverter/charger should be able to float charge the coach and house battery banks". Well, this is one of the times when I try and emphasise for new (if this coach is new to you) owners, to take the time to sit down and take an evening or two, or three and read through any and all owners manuals and leaflets or supplements that came with your coach, that may be a form of instructional material. Some of that info, if it's there, could be a great learning tool for you to get to know your coach and, its systems.

Now, this is not chastising you in any way, shape or form. None of us mind helping folks here. We were all there too and, for many cases, are still learning. Now, first off, different manufacturers do things differently. And, not only that, they quite often vary their operations/installs/wiring/components from year to year. So, what's done on a year prior to yours, may not be done on yours. You say you BELIEVE that your inverter/charger handles both sets of batteries. Well, maybe it does and maybe it doesn't.

On our '04 Itasca Horizon 36GD with the C-7 330HP CAT, the inverter/charger ONLY charges the house batteries, when on shore power. I added the "Amp-L-Start" a few years ago to help maintain the chassis batteries. And speaking of that, you also say your unit is equipped with the Trik-L-Start, correct? If so, two things. One, the Trik-L-Start is NOT a battery charger. It's primary job is to analyze the two different battery sets, house and chassis. When on shore power, and your inverter/charger is charging the house batteries. When wired correctly, (not hard, only three wires) the Trik-L-Start will look at the voltages of both sets of batteries.

When it sees the chassis batteries as being .5v lower than the house batteries, it jumps into action. And it does so by ALLOWING some of the amperage being sent to the house batteries, to be diverted to the chassis batteries. The Trik-L-Start allows a maximum of 5 amps to the chassis batteries. It's newer brother, the one I have, the Amp-L-Start, allows a maximum of 15 amps to the chassis batteries.

Now, was your coach equipped with the Trik-L-Start from the factory, I don't have a clue. But, if so, than if and when your coach is plugged into shore power or, it's being powered from the generator, then your inverter/charger IS charging both sets of batteries, but, it's only charging the chassis batteries THROUGH the Trik-L-Start. And that should be quite enough charge to keep your chassis batteries at full voltage unless, you have a massive draw. Like say, maybe compartment lights left on or, interior lights left on, or some other draw or short.

Now, that sort-a takes care of your inverter/charger operation. As for solar, well, solar is good IF you have good sunlight. Many coach builders install a cheap-o 5W or 10W solar panel that's barely enough charging to keep the house or chassis set of batteries charged, depending on what kind of parasitic draws are designed into either system. Of course, the larger the solar system, the more capacity for charging. As for the two large, what appears as auxiliary cables attached to your battery positives, well, I don't know your coach and, who wired it so, for me to make an "assumption" of what they are and where they go, would be a mistake on my part.

The wiring from either set of batteries, cables and all, I've seen multiple ways of doing it. So, again, what's on one coach, might be different on the same coach of a year prior or a year newer. If there are no labels of any type, I'd have to trace those two "extra" cables to their destination. If as someone has suggested, one goes to the ECM of the engine, well maybe so. I'm by far, no expert.

But, what I'd do if it were me, and I was having any sort of battery problems, especially with the chassis set, I'd pull both of them, run them down to a place that can put a good load on them have them load tested. If they pass that test, then you know the batts are in good shape. Now it's time to analyze the shore powered charging system. Good luck.
Scott
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Old 08-03-2018, 01:51 PM   #11
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The actual voltages for 12 volt batteries, or pairs of 6 volt batteries in series (usually golf cart batteries) are as follows with no load and no charge coming in: 12.8 is fully charged. 12.2 is 50% discharged. You should endeavor to NEVER let the voltage drop below 12.0. When the voltage is low, the starter motor draws a LOT of extra current and low voltage is the usuall cause of burning out a starter. One idea is once you've gotten things straightened out is to add solar panel(s) so that you are always adding to the batteries whether it is sitting, running, or plugged in. I found that solar can burn out an alternator stator when the two are both supplying current to the batteries, so I always disconnect the solar panels when underway. One beauty is that if you run your batteries down overnight, when the sun comes out you will soon have enough to start the genset which will quickly supply enough charge to start the main engine. Peter
I found that solar can burn out an alternator stator when the two are both supplying current to the batteries, so I always disconnect the solar panels when underway.


How did you come up with that detetmanation ?

Many, many others, including myself, leave the solar, or even the generator & converter, running and charging the batteries, while the engine mounted alternator is also charging, with no burned out stators.

The only way for current to get to the alternator stator is if the diodes short out. If that happens, the battery itself can burn out the stator.

If an alternator fails, its not a properly connected solar chargers fault.
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Old 08-03-2018, 11:52 PM   #12
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I found that solar can burn out an alternator stator when the two are both supplying current to the batteries, so I always disconnect the solar panels when underway.


How did you come up with that detetmanation ?

Many, many others, including myself, leave the solar, or even the generator & converter, running and charging the batteries, while the engine mounted alternator is also charging, with no burned out stators.

The only way for current to get to the alternator stator is if the diodes short out. If that happens, the battery itself can burn out the stator.

If an alternator fails, its not a properly connected solar chargers fault.

When I first got my '02 Travel Supreme (400 hp Cummins/Allison) I took the alternator to a trusted shop and it was pronounced perfect - brushes barely broken in at 44,000 miles. On my initial trip after 5 or 6,000 miles the alternator failed. The idiot shop it was taken to replaced the brushes, which were fine, and returned it to the mechanic who removed it. It failed inside of 3 miles and so I went back to the same mechanic. THIS time the shop dug deeper and found the stator was fried. Different coaches may be wired differently, and I was assuming that each charging device had voltage sensing and would both back off when the batteries were floating. In this case I was wrong - the solar goes through a controller and is of high quality, but in the 30,000 miles I have driven since turning the solar off when underway I have had no issues. Might be a wrong assumption on my part, but the solar doesn't do anything underway as the alternator puts out 140 amps so maybe it's witchcraft, or maybe the 500 watts of solar did indeed fry the alternator stator. I also carry a spare alternator as this is something you cannot do without and you might not find the right one if you do suffer a failure on the road. This was just my experience, and it's easy enough to add shutting off the solar to my pre-flight check list. Peter
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