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Old 03-05-2015, 09:15 PM   #1
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How can I determine if I have a separator/isolator?

I'm on my first trip in my new-to-me 1989 SMB.

I'm pretty sure I have a house battery that needs to be replaced. It took a charge when plugged in at home on shore power but quickly ran down and now doesn't want to come back up to above 12v while driving, even for extended periods of time.

The first night sleeping in the rig the only thing drawing from the house battery was the fan for the furnace, I had it set really low so it wasn't kicking on very often. In the morning I noticed that the house battery was down around 11.5v. I had suspected I'd need to replace the house battery so this wasn't that big of a deal, the previous owner had let it sit for 2 years without any kind of charging device on it and without driving the SMB.

What was more of a problem is that it also seemed to draw down the starting battery. It barely started that morning.

I had been told by the PO that they were "separated" but he didn't go into specifics of how and I'm just now learning about all this stuff so I wasn't exactly asking the right questions.

I don't see anything that looks like a separator but I'm also not sure where/what to look for.

I do have a Xantrex panel which looks just like this:


As I was told, originally SMB spec'd 2 batteries under the hood, one for starting and one house. My SMB has since been upgraded with a much larger house battery under the seat. The PO was kind of vague on the details but I think he said that the house battery under the seat and the house battery under the hood are connected and are separated from starter battery. Unfortunately that doesn't seem to be the case. Does this sound right?

Unfortunately I don't have my multi meter with me but when I get home from this trip I plan to start poking around, I'm just not entirely sure where to poke.

Thanks,
Dan

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Old 03-05-2015, 09:39 PM   #2
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Re: How can I determine if I have a separator/isolator?

Just follow the positive battery lead from the battery under the seat; it should connect to a separator if you have one. If there is more than one positive cable coming off of your house battery, follow both of them; it's highly likely one of those cables connects to your inverter.
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Old 03-05-2015, 09:54 PM   #3
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Re: How can I determine if I have a separator/isolator?

I know you don't have a volt meter but if you have a separator (most are bi-directional) you'll see the voltage at the starting battery and the house battery jump up when you plug into shore power and turn on the shore charger. If you have an isolator you'll only see the jump in voltage at the house and starting battery when the engine is running. So when on a shore charge the engine battery does not receive any charge. This is provided everything is working correctly. A bad isolator or separator can act like an open switch. Sometimes Isolators can corrode up which can generate a ghost draw which has been a problem for some SMB builds in the past. SMB usually put the isolators under the hood and separators towards the rear but they can be installed almost anywhere.
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Old 03-06-2015, 06:33 AM   #4
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Re: How can I determine if I have a separator/isolator?

Side story: I bought my van in North Carolina and drove it back home to Philadelphia. It had been sitting for quite a while in the previous owner's driveway. After a few hours on the road at night, all of a sudden most of the lights in the rear coach started lighting up. Totally confused me for a while as I crawled around my new van trying to figure out how to turn the lights off and why they came on in the first place. But then I realized that the aux battery had started to take a charge from the alternator while driving.
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Old 03-06-2015, 07:58 AM   #5
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Re: How can I determine if I have a separator/isolator?

Seems it's getting worse. Just woke up to a totally dead starter battery, won't even turn over. House batt panel is reading 10.5, was at 11.5 when I went to bed. Nothing should be drawing from it.

Is it normal for the inverter to hum constantly?
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Old 03-06-2015, 08:14 AM   #6
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Re: How can I determine if I have a separator/isolator?

Quote:
Originally Posted by dfinn

Is it normal for the inverter to hum constantly?
Not really....only when it's on. When running it draws idle current from the battery even when not in use. You should be able to turn it off with a switch on the inverter or on the remote panel for the inverter.

Typical use case is: turn on the inverter, use whatever 110V stuff you need, turn off the inverter to save battery.
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Old 03-06-2015, 09:21 AM   #7
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Re: How can I determine if I have a separator/isolator?

https://flic.kr/p/rdiEhp

That's what it looks like under the couch, sorry for the bad pic, tough spot to get into.

Main pos goes to the block in the floor which I'm assuming is connected to the alternator? From there it goes to the inverter. The other smaller wires coming off the pos go to the fuse panel.

Sounds like it might be under the hood as daveb said?
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Old 03-06-2015, 10:17 AM   #8
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Re: How can I determine if I have a separator/isolator?

Since your van is a 89, it most likely had a isolator when it started out.



This of course cold have been changed at anytime. Since the PO said that there are two house batteries, one under the hood and the added one in the back, I would expect to see the isolator or separator up under the hood between the starter and house battery under the hood.

Here are pictures of the two separators that have been used by SMB
SurePower


BlueSea (Note: It could have a yellow knob on top)


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Old 03-06-2015, 11:27 AM   #9
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Re: How can I determine if I have a separator/isolator?

Found it. It's mounted in front of the battery on the drivers side. Both batteries under the hood are wired together, connected via the pos terminals.

I'm at a mechanic now who thinks both are shot. Both are optima blue tops.
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