Coach Battery not charging, issue

[Jeffrey]

My brother and I have almost identical 91 Winnebago Coaches and he just returned from a trip to Yellowstone yesterday (he stores his unit at my place) and when he brought it in, his coach battery was on it's last breath. It is my understanding that the coach battery is either charged by the Engine Alternator, while the engine is running, or, by AC shore power (or on board generator). I'm curious, does the engine/alternator, when running, charge the coach battery directly or does the "power" go through the converter/battery charger then to the battery? If the engine/alternator charges directly, how does it do it? If not, how does that indirect route do it? I'm not, nor is my brother, an electrician, but most the time were able to use logic and the power of deduction to figure "most" reasonably simple things out.

I put a voltage meter on the truck batter and when the alternator kicked in the voltage eventually jumped to 14 plus, so the alternator is working.

However, the voltage at the positive and negative cables at the coach batter started out (when engine was running) at 7.5 volts, then a little bit later, 3.6 volts, then a little bit later (10 minutes or so) 7.5 volts again. Would that indicate a short somewhere in the wiring? Same thing happened when hooked to AC shore power.

Does both the AC power and Engine alternator power go through the on board battercharger/converter? Am I making sense, here?

I suspect there is either a short in the wiring or the converter has an issue or the battery charger has an issue or both have an issue or the issue is all three. Am I getting warm on this?

Any suggestions, comments, questions to my questions, (or, if I need to be more specific in some area) would be a help.

Thanks

Jeffrey

[Jeffrey]

Excellent question. It "appears" (small red sticker "4/11") it's a little over two years old. I just (trickle) charged the battery over night and will test it shortly. Let's just say the battery is good, for the time being. The reason I say that is because, regardless of the battery's health, I'm still curious as to the answers to my original questions, i.e. how the charging system works.

thanks

[waiter]

Your coach battery should charge from the truck when its running, or from shore power when plugged in.

Reading across the batteries when the truck is running, you should get around 14 volts at both batteries.

The fact that your reading 7 volts at the coach battery on both shore power and truck running seems to make me think you have a broken wire or faulty self resetting breaker somewhere in the battery line.

Its also possible your battery could have shorted cells.

Is this a new coach battery?

One test you might do, disconnect the coach battery, and check th evoltage on the battery, and on the wire you just removed from the battery.

ALSO - Do the coach lights work when on shore power with the battery disconnected. What happens to them when you connect the battery.

JOhn Mc

88 Dolphin 4 Auto

[Jeffrey]

"Your coach battery should charge from the truck when its running, or from shore power when plugged in."

The battery does not seem to be charging from either.

"Reading across the batteries when the truck is running, you should get around 14 volts at both batteries."

Yes to the truck battery and no to the coach battery. (3.6 to 7.5 have been the two readings thus far. I have not put the fully charged battery back in the rig. It's raining and I've been busy all day. Will tomorrow and give an update)

"The fact that your reading 7 volts at the coach battery on both shore power and truck running seems to make me think you have a broken wire or faulty self resetting breaker somewhere in the battery line."

I agree. What are the (two in my coach battery compartment and three in my brothers coach battery compartment) small "shunts"(?) that come off the positive wire and are attached to the compartment wall? I'm getting a "ping", i.e. complete circuit, on my voltage meter indicating they aren't blown(?).

"Its also possible your battery could have shorted cells."

I'm assuming "shorted cells" occurs when one cell goes dry? We topped them up with distilled yesterday but the lead plates were still under water.

Is this a new coach battery?

The battery was in the unit when my brother bought the Toy Home last spring. It "appears" to be "new" from it's external condition even though the tag reads "4/11"

"One test you might do, disconnect the coach battery, and check th evoltage on the battery, and on the wire you just removed from the battery."

I'll do that tomorrow when I hook the battery up.

"ALSO - Do the coach lights work when on shore power with the battery disconnected. What happens to them when you connect the battery."

I'll check those tomorrow too. Appreciate your info thus far.

[Maineah]

There is also an isolator in the mix. This device seperates your truck from the coach when the engine is not running the reasoning is to keep your truck battery from being discharged by the lighting etc in the coach. The converter/charger should charge your battery and run the lighting in the coach while it is plugged in it does not have a connection to the truck or need to have the truck running to charge and yes if the generator is running it should charge but it might take a long time depending on the converter/ charger. First step have the battery checked and charged then see about the charging systems

[fred heath]

I had a similar situation several months ago. It came back to a bad chassis ground on the coach battery. Worth a check.

[Jeffrey]

Thanks waiter, Maineah and Fred H.

So, I just returned from a auto parts store where they checked the Battery and found it to be in excellent health. Went out to the rig and put a volt meter on the coach battery cables without the battery hooked up. The meter read 2.1 volts. Then, I turned the engine on and immediately the volt meter indicated 1.3 volts. Then, after the alternator kicked in, the volts went to 1.1.

waiter

the coach lights work when shore power is on and when just battery is now hooked up (shore power off)

Maineah

Are the "isolators" the small boxes that are on the inside wall of the coach battery compartment that seem to be "fuses" or "shunts"; positive cable connects to them? If so, they "seem" to be functional, i.e. when I hook the volt meter on it and turn the dial to get a "beep" if the circuit is complete, and hook them to the "Isolators/Shunts/Fuses" in that compartment, each one seems normal.

Fred

My brother cleaned that connection two days ago so thanks for that suggestion but that doesn't seem to be the issue.

It seems that the problem might be somewhere where the wires "Y" (from truck battery/alternator and from the shore power) TO where the cables run into the coach battery compartment. Sound logical?

[Jeffrey]

I forgot to mention. As I mentioned in the above post, I had some slight voltage readings (when the coach battery wasn't hooked up) from the coach battery cables prior to starting the engine and a slight change after starting the engine. When I checked the cables when I turned on shore power they were low but not the same. When turned off the shore power, an entirely new (low) reading was indicated, i.e. the low readings all over the place.

[WME]

Is the volt meter good? Check the battery on a different car to see.

The reason I ask is all of your readings have been wonkers.

[Jeffrey]

The volt meter is good, I believe. Just checked 3 different batteries (3 different vehicles) and all gave readings between 12.10 and 12.20. The "wonker" readings you are suggesting all come solely from the coach battery cables when the battery in the coach is not hooked up (engine off/shore power off, engine on/shore off, engine off/shore on, and then, etc). Definitely different there, or "wonkers" as you put it. Could it be those erratic numbers indicate a "short" in the wiring system?

[fred heath]

Digital volt meters are very sensitive. Try with an analog meter and see if you have the same wonker readings.

[Maineah]

Do you have any ideal about what isolator you have? It will be under the hood. One is a metal can with two heavy wires and one small one the other one is a 4 wire type with little cooling fins. The little small boxes are self resetting circuit breakers you should have the same voltage on both terminals. Your voltage reading at that low a voltage does not mean much if you hold on to both leads of the meter with your hands you'll get the same kind of reading. Some thing is not connected or the circuit breaker, isolator, etc,is toes up. Usually volt meters only beep during the ohms setting not voltage. Your coach battery is doing what it should lighting the lights with the engine off and not plugged in so it has voltage the cables not hooked up most likely will not show any voltage. Once the engine is started (as long as the coach battery is hooked up) should read some thing close to the truck battery voltage at the coach battery.

[waiter]

Hook the coach battery back up, Plug in Shore power.

Turn on your coach lights, do they work with the coach battery connected and shore power connected?

Now unplug shore power, The coach lights should still be lit, running off the coach battery?

Sounds like there is a wiring problem from the converter to the coach battery.

John Mc

88 Dolphin 4 Auto

Now sta

[Jeffrey]

Thanks Maineah

John Mc

Yes, lights working off Shore Battery.

Yes, lights working off Coach Battery.

If there is a wiring issue between the converter to the coach battery, why would the battery go dead, after 500 miles of driving a couple of days ago, if the coach battery is suppose to be charged by the engine alternator? Does the wiring go from the engine/alternator through the "converter/battery charger" then to the coach battery? I assumed one set of wires from converter/battery charger to coach battery and another set of wires from engine/alternator to coach battery. Yes? No?

[fred heath]

I agree with John. Check all your terminal connections on the heavy wire going from the converter to the coach battery. If all are good, physically check the wire itself for any breaks or wear through. Especially the areas where the wire passes through any openings.

[Derek up North]

After 20 - 30 years, it wouldn't hurt to disconnect, clean and reconnect (with some dielectric grease) every connection you come across.

[waiter]

WAIT - If the coach lights are working when your not plugged into shore power and the truck isn't running, it sounds like everything is working.

Coach lights, Stove hood light and fan, and the furnace, should all work, with no shore power and no truck running.

If this is true, whats the problem again??

John Mc

88 Dolphin 4 Auto

[Maineah]

Two sets of wires one for the truck charging system one for the converter. The battery charge wire from the coach goes up front to an isolator in between there maybe auto reset circuit breakers if the coach battery is not being charged by the truck there is a problem in between the front and the back, wiring, isolator, or circuit breakers. As far as the converter/charger it does nothing unless the MH is plugged in. If your converter has been replaced with a more modern one the truck charge wire may go to a big terminal on the converter but it still does not have any effect on the charging system from the truck it's just a connection point to the battery.

[Jeffrey]

The problem is that the Coach Battery is not charging. Had it checked out yesterday and the battery is good. neither the engine alternator nor the shore power (battery charger/converter) are charging it.

I'll check the isolator, Maineah, but that system charges the coach battery from the engine/alternator, whereas neither charging system seems to be working.

I'll go out now, it stopped raining, and see about the connections, again. Then, if they are clean, I'll see if a wire is shorting (somewhere?!?).

[waiter]

If the lights are working without shore power or the truck running, this tells me your getting good connectivity thru the battery, converter, and lights.I cannot explain how you could be reading the low voltages that your seeing. The fact that the lights are working says the voltage is probably OK.

If you disconnect the battery, and the lights are working with shore power, this tells me the converter is working.

If you disconnect the battery, then start the truck (disconnect shore power) if the lights work, this tells me you have good connectivity from the truck charging system to the converter (thru the isolator)

John Mc

88 Dolphin 4 Auto

[Jeffrey]

"If the lights are working without shore power or the truck running, this tells me your getting good connectivity thru the battery, converter, and lights."

Yes, they are

"I cannot explain how you could be reading the low voltages that your seeing. The fact that the lights are working says the voltage is probably OK."

We'll pass on that one for the moment.

"If you disconnect the battery, and the lights are working with shore power, this tells me the converter is working."

Yes, I disconnected the battery and the lights are working with shore power. So, the converter is working.

"If you disconnect the battery, then start the truck (disconnect shore power) if the lights work, this tells me you have good connectivity from the truck charging system to the converter (thru the isolator)"

No, the lights do not work when the shore power is disconnected, the battery is disconnected and the truck engine is running.

Is that the key? The culprit? The Isolator? What Maineah, and now you, are pointing out/suggesting to me?

[waiter]

Isolator, No, not yet. I'm still vary confused by the symptoms/

Do what I said about checking coach lights

1) No Shore power, no truck running, coach battery connected. Do coach lights work?

2) No Shore Power, truck running, coach battery disconnected, Do coach lights work

3) Shore power, no truck running, coach battery disconnected, Do coach lights work?

John Mc

88 Dolphin 4 Auto

[Bob C]

I believe that the confusion comes from the fact that when the brother got back from the trip,. the battery was dead. He charged it with a battery charger, not the converter or alternator and now has a fully charged battery. It did not get any charge from the converter or the alternator.

I replaced all of my self-resetting circuit breakers and cleaned all of the connections when I was having my electrical problems. It took care of a lot of power loss.

When I was trouble shooting, I started by making a ground wire that hooked straight to the truck (front) battery so that I was always using a known, good ground. I know that by using a really long ground wire, I was loosing some voltage but I wanted to have a good ground for every test.

I checked voltage from front to back.

1. truck battery voltage while engine off and also running

2. alternator voltage

3. isolator voltage leading to the truck battery

4. isolator voltage leading to the coach battery

5. voltage going into circuit breakers

6. voltage coming out of circuit breakers

7. voltage to coach battery

I also checked my coach battery ground for continuity with the truck battery ground. This was one thing that I almost forgot and I determined that my coach battery had a poor ground.

Work systematically at the problem. Hit and miss testing will almost always be a miss at finding the problem.

[Jeffrey]

Thanks Bob C and thanks to everyone who gave advice, all good information to build on. I believe the problem was the cable from the positive truck battery to the Isolator. I'll verify and validate that in the next day or so when I have time to get back to this "project".

Thanks all, again.

Jeffrey

[Maineah]

It would help a bit if you can tell us what type of isolator you have they work differently but do the same thing. The solid state one has cooling fins the relay type does not.both have fairly heavy wires attached and usually are connected thru circuit breakers with terminals and held down by small nuts they will be under the hood.

[Jeffrey]

Hi Maineah

Mine looks like this one (more or less), if it copied to this post here (silver cylinder with 3 posts coming out of it, attached to wall of wheel well in engine compartment). I determined it was a short in the cable that goes to the Isolator, rather, the "switch" (or whatever that gizmo is) prior to the isolator. So all seems to be well now.

Thanks for your help, Maineah. By the way, what does "Maineah" mean? Your name?

[Maineah]

Good that is an easy one! Here is how it works; the small terminal turns it on it is energized by the key switch and goes on with the engine it should have power when the key is on. Use your volt meter to check for power, one lead on the body of the relay the other on the small terminal with the key on something in the order of 12 volts. Next check both big terminals they both should have 12 volts if neither one does look for a circuit breaker (a small box with 2 terminals) it will be nearby one is from the truck battery it is the key it has to have power on both posts or the isolator cannot work. The terminals on the breakers do get nasty rusty and the chance of getting them apart to clean them is slim they most likely will break but auto parts stores have them they are 35 amp. The relay is nothing more than an on/off switch operated electrically so with the key on both batteries at connected together. Once you have power on both big terminals follow the wire to the next breaker it is for the coach same drill power on both terminals or it won’t charger the coach battery when that is all good then on to the coach battery at this point it should be showing a charge. Maineah is “one that lives in Maine”