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Old 05-07-2019, 06:21 PM   #1
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Default Battery Isolator Question

I posted in March about my battery isolator partially melting at Christmas time. I have a 1999 RT 190P. There was just a hole where the left post used to be. My mechanic, who isn't an RV mechanic per se but has worked on my RV, replaced the battery isolator with a 200 amp Cole Hersee, but I'm wondering if he has it installed correctly. I can't tell that the coach battery is getting charged by the engine battery.

At Christmas, I was plugged into electricity for a week, so when the isolator melted, I expected the coach battery to have a full charge. When I got it back from the mechanic, however, it was showing a half charge. So, I'm not sure why it was at half charge, but it was still at half charge when the isolator was replaced. When I took it back to my mechanic to check on the connection, he thought the coach battery was toast. He said he put a load on it (I need to ask him what he did specifically), and the battery was done for. So, he replaced the coach battery last week.

Does a new coach battery come charged, or do you need to charge it up? It was initially showing a half charge. I drove 11 hours this past Thursday, and then it showed 3/4 charge. I was plugged into electricity for 3 days, and, right after I unplugged from electricity, it was showing a full charge. After driving 5 hours Sunday night, it was back to 3/4 charge. I would have expected it to have a full charge, based on my previous Class B's.

So, here is my question. The previous isolator was positioned so the label was on the back side, and I couldn't see it. The new one has the label facing front. The engine battery is connected to the Battery 2 terminal, and the coach battery is connected to the Battery 1 terminal, per the labels on the isolator. I asked my mechanic if the engine battery needed to be connected to the Battery 1 terminal, and he said it doesn't matter. According to the directions I've seen on-line and from another thread on here, it looks like the engine battery is normally connected to the Battery 1 terminal. I know the isolator is unidirectional, so it seems to me that it would matter. Does it? And, if it does, can I just change the wires if they'll reach (I'm not sure that they will), and do I need to do anything else before changing those wires so I don't get shocked from the batteries?

Thanks!
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Old 05-07-2019, 08:26 PM   #2
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Pam, I can not answer your isolator question, but concerning this:

"I can't tell that the coach battery is getting charged by the engine battery."

It is simple and easy to tell if the alternator is charging the rv battery. The battery is charging if the battery voltage is there 13 or 14 something voltages with a battery voltage meter or the LED lights. When the engine is running, it will show full charge as those lights mean a specific battery voltage. If you plug into shore power, same thing if the charger is working.
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Old 05-07-2019, 10:05 PM   #3
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Basically the connections to the isolator are as follows: The large center terminal goes to the alternator, one of the outside terminals connects to the starting battery and the other goes to the house battery through a small circuit breaker usually mounted on the isolator itself or very close by: these circuit breakers frequently fail. They are cheap, $5 at NAPA or AutoZone and there are 2 of them, one at the isolator and the other at the house battery relay (the thing that clunks when you switch your house battery on and off). I would replace both of them if the battery indicator is not showing C (green) when you have the engine running. You can test with a voltmeter ($15 at harbor freight): one probe on a good ground point and the other on; first the alternator post on the isolator, second on the starting battery side of the isolator and last on the house battery terminal. The first reading should be about 14 volts plus or minus, the other readings should be about 1/2 volt lower. (engine running) If that test passes and the battery indicator indicator is not on green, definitely replace the circuit breakers. They are about 1"x3/4"x1/2"with 2 stud terminals on the top. They are usually 40 or 50 amp rating, marked on the side.
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Old 05-16-2019, 05:41 PM   #4
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Update: Thank you both for the information. I wasn't really clear though on what I was looking for in terms of the circuit breaker and where it was located. I definitely couldn't find one near the isolator. I posted the question on a Roadtrek owners Facebook page (for older Roadtreks) and some of the members posted pictures of the circuit breaker and the location. They also told me to disconnect the negative terminal on the coach battery before changing the circuit breaker. I know I read this someplace else, but they also found that not all of the Roadtreks have a circuit breaker near the isolator. It just has one near the coach battery.

The circuit breaker is underneath the driver's side twin bed, behind the regular circuit breaker panel. There are 2 circuit breakers there, and it was the lower one. As soon as I saw it, even I could tell it was fried. The plastic at the base of the left post (the shorter post) was distended. When I tried to take the nut off, the post came out with it.

The circuit breaker was a 30 amp, but 2 of the men told me it should be a 50 amp. The other circuit breaker above it is a 30 amp, and one man said he had a 30 amp and a 50 amp in his Roadtrek. So I installed a 50 amp but then found out that it really should be a 30 amp, so I installed a 30 amp last night. Everything is working great now!

I thought that the monitor panel should show the coach battery as being fully charged while the engine is running, but it was still showing as only half charged. Well, I hadn't paid attention to the letters next to the lights on the Roadtrek's panel, and the one of the men on the Facebook group explained what the letters are. In the Coach House I had, all 4 lights would be lit up when it was fully charged. Anyway, that's what I remember. In the Roadtrek, I didn't realize the top light just meant it was charging, etc. So the old battery was showing 2 lights since it wasn't getting charged by the engine. I'm assuming the old battery probably didn't need to be replaced yet since the circuit breaker was the reason it wasn't charging. I'm thinking about going back to my mechanic and showing him the bad circuit breaker, just so he knows, in case he has this ever come up again.

Now that I've gone through all of this and gotten the breaker changed, I understand more of what you both wrote. First time I've done anything like this, and I think I need to buy some more tools. Fortunately I was able to make what I have work.

Thanks for your help!
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Old 05-16-2019, 05:43 PM   #5
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It was the lower circuit breaker that was bad. This is the 50 amp that I had installed, which I replaced last night.
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File Type: jpg Circuit Breakers.jpg (86.5 KB, 15 views)
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Old 05-16-2019, 06:11 PM   #6
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Awesome update and thanks for posting it.

If you or anyone one else wants more info on the Kib brand state of charge panel lights and what they mean I posted some info here: http://www.classbforum.com/forums/f5...ghts-2295.html
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