Battery Isolators - how long should they last?

[Mike]

Hello everyone,
I had some battery issues last year, and part of that chapter in my RV experience
included a dead chassis battery after we left the coach batteries on for a few days straight,
maybe as long as a week. I've trolled some of the threads on here with "isolator" as a keyword, but
can't find anything about why the isolator wouldn't protect the chassis battery from drain
when we left the coach batteries on. It's an '02 RT 190P. It's just been puzzling me for a few
days now. Actually, I'm not even sure I'd know which thing under the hood WAS the isolator.
Any hints on that would be appreciated, as I intend to try to "jump" the outer posts on the isolator,
as some have suggested, next time I have a dead chassis battery, to see if I can start the engine.
Maybe I should take it in to a repair facility and get it (the isolator) checked? Do they last forever
or do they have a fairly finite functional lifespan? Would a GM/Chevy dealer know what to check?

Ta in advance for any thoughts/suggestions/theories.

[markopolo]

The isolator in my Roadtrek was the color red. It looked like a large heatsink with the cooling fins.

viewtopic.php?f=12&t=453&p=1038



They should last a long time but not forever.

In my RT the chassis battery would be dead after 3 weeks of no use. Power locks, compass, radio all take a bit current.

The "trunk" light is powered by the chassis battery. If your camping gear moved and knocked the switch into the on position it would drain the chassis battery overnight.

[Mike]

Hi,
I saw that pic of your isolator bridge, but I wasn't sure whether it was the RT or the R-Vision.
I'll have a look under the hood near something with a pulley and belt.
I haven't had a problem for a while, but I try to start and drive as often as is reasonable, and
weather permitting in the winter months. And we haven't left the coach batteries enabled for
days on end.
I've got a multi-meter and was thinking there should be (almost) zero draw on the chassis battery
with the engine off and the coach batteries enabled, but I have no idea how to test for a significant
change in draw on the chassis battery.
Suggestion? Red lead on the positive post, black on the frame somewhere,
and enable/disable the coach batteries? Or, disconnect the positive battery cable and use
the mm as a bridge between the positive post and the cable end? Set at 20V?
There shouldn't be any change in draw when the coach batteries are on, I'd think?
I checked the courtesy light in the very back and it's on " door open/activate". It's
also an LED bulb now, so it might take a bit longer to drain the chassis battery.

Electrically challenged Mike.

[markopolo]

You need to look for amp draw not voltage.

Your multimeter might measure amps. If so, you disconnect the negative battery cable put the meter between the detached cable and the negative battery post with your meter on the amp setting.

Some multimeters are only capable of measuring up to 500 milliamps and will burn out if you try to measure more. I wrecked one trying to measure parasitic draw. I my case the parasitic draw may have been 200 milliamps but the draw surges after you reestablish the the circuit. The vehicle computer uses more current for a minute or two when reconnected to the battery.

I couldn't figure out how to connect up the multimeter and then disconnect the negative cable so that the circuit was not interrupted (I didn't have alligator clips, only had probes) so the initial surge wrecked my multimeter.

It would be much easier to use a clamp on ammeter. Link: viewtopic.php?f=29&t=1038

[Mike]

I think it does measure amps. So, bridge between the negative cable and negative battery post using the mm on "amp"?
Then enable the coach batteries switch and look for a drop in amperage at the chassis battery? Will it be a sizable drop or am I looking for milliamps, do you think? Or if there's any change at all in amperage, there's a problem?
Here's another theoretical question. Do all the batteries on board share the same ground (the van's frame) and could that be the common denominator causing the draw down of the chassis battery with the coach batteries left on?
I only have probes too. I'll give it a try. Maybe I can get my wife to help.
Thinking about what you've suggested, do you think there's a way to determine if there's a problem at the isolator itself?
Shouldn't there be zero change in the draw/amps on the chassis side of the isolator (assuming I can figure out which side that is) with engine off and the coach batteries enabled and disabled? I was just looking for an easier way to test this. The isolator posts might be easier to work with.

Sorry for all the follow up questions, but I am clearly electrically challenged.

Mike.

[markopolo]

Originally Posted by Mike

So, bridge between the negative cable and negative battery post using the mm on "amp"?

Yes, but I'd only do that if your multimeter can handle more than milliamps. If it has a 10A DC setting for example that's what I'd use. If the highest setting is 200ma dc I wouldn't use it just in case the current draw is higher.

Originally Posted by Mike

Then enable the coach batteries switch and look for a drop in amperage at the chassis battery?

Measuring amps shows the amount of current used.

I may have confused the issue a bit. You originally mentioned volts and you could do some testing that way. Voltage would drop if there's a load. For example, if the chassis battery measures 12.6V and the house battery measures 12.3V with the coach batteries switch off and then you turn the coach batteries switch on and you measure 12.6V at the house batteries then they are definitely drawing from the chassis battery. Not good if the motor is off.

I did a similar test on the weekend. I started the motor, measured the voltage at the chassis battery, then measured the voltage at the house batteries to make sure the house batteries were being charged by the alternator. Often there will be a bit off a voltage drop due to cabling and the isolator. I measured 14.4V chassis battery and I think 14V at the house batteries. Good enough for me.

Originally Posted by Mike

Here's another theoretical question. Do all the batteries on board share the same ground (the van's frame) and could that be the common denominator causing the draw down of the chassis battery with the coach batteries left on?

I've wondered about this also - I just don't have the knowledge to be able to answer the question. Hopefully someone will answer it for us.

Originally Posted by Mike

Thinking about what you've suggested, do you think there's a way to determine if there's a problem at the isolator itself?

First, I'd plug in the van and take voltage measurements on the chassis and house batteries. Basically, with an isolator, you want voltage to pass through the isolator only from the alternator (chassis battery) to the house batteries - not the other way around. When your van is plugged in you'll measure more than 13.5V at the house batteries. The chassis battery will read less than that. If the house batteries measure 14.4V and the chassis battery reads the same then they are not "isolated". That's either a faulty isolator or you have a "battery combiner" (it is better than an isolator).

Second, I'd do the test that I did last weekend (mentioned above) to make sure the alternator is charging the house batteries.

You can perform a continuity test on your isolator:



I mentioned the isolator in my Roadtrek was red. Often they are silver unpainted metal and cylindrical in shape with a post on either side and smaller post in the middle.

[markopolo]

A few notes:

A fully charged, rested battery won't measure more than 12.7V.

My Roadtrek (Class B) had a pretty good quality isolator: http://www.hehr-international.com/isolators.htm It was mounted at the top of the firewall in the engine compartment

My R-Vision (B+) had a battery combiner - the chassis battery got charged when the RV was plugged into grid power - sweet! It was mounted under the vehicle on the frame.

My Bigfoot (Class C) has the silver cylindrical shaped isolator. It is located in the coach under the fridge.

[Mike]

Thanks for all the ideas. I'll try them and see what I can find out.
First, mission locate isolator/combiner. Those pics will help.

[Mike]

Update: I found that RT electrical simulator online and, just for fun, emailed/contacted the author with my questions.
He owns a 2002 RT 190V which I figured would be similar electrically to mine, and he helped me locate the isolator.
It's bolted to the inside of the frame almost directly below the battery. Very awkward to reach for self diagnostics,
since I have a gravel driveway. If I'm going to replace it anyway, I'll get them to double check it first as part of the
service. It was not bypassed from what I could see and mine looks identical to the pictures you both posted/sent for me.

He (John) said just measure any draw at the fully charged Vehicle-battery once the surface charge has dissipated,
with the disconnect switch disabled/off to get a starting point, and again with it enabled/on to see the rate
of draw down on the V-battery. He suggested turning on a few interior lights to increase the draw. Also, the propane and
CO detectors wake up and start to draw as well.
Theory (my theory): This should only draw down the Auxilliary batteries, if the isolator is functioning as designed. There should be no noticeable draw at the V-battery.

Soon after running the engine over an hour of driving, I get around 13V at the V-batt. As you and John have said, there
must be surface charge present. Time to let it sit for a while. I actually was doing some other plumbing stuff with the RV and had the interior dome lights on and off as I opened and closed the doors.
I did my first test yesterday after letting the V-battery rest for a while after an hour run around the town to charge it.
The rest period was about 1 hour. So I measured 12.58 V on the V-batt with engine and ignition off and battery disconnect disabled/off. I tested the voltage several times over the next hour or so, and it actually crept up to 12.63V. Several more tests showed a steady 12.63V without any more ups or downs. I assume it is now fully charged, and any surface charge has dissipated.
I then enabled the battery disconnect switch and measured every half hour for about the next 2 hours.
The final test showed a V-batt voltage of 12.25V, which I would call a significant drop.
I ran this by John and he said probably a shorted diode in the isolator. I'm waiting for 2 Roadtrek service centres to
get back to me with prices for replacing the isolator.

If anyone else has problems with their 2002 Chevy isolator, here's a couple of links John sent me.
Isolator pic.....
http://www.roadtrekchapter.org/REGION7/ ... olator.jpg
very much like the pic you posted up.
Testing the isolator from Hehr .....(pdf file) very comprehensive.
http://www.hehr-international.com/pdf/delcoisoman.PDF

While we're on the electrical problem hunt, I noticed that my shore power cord looks "spliced" about 2 feet
from the spot where it dissappears into the interior of the vehicle. Is that normal? I've seen a couple of
power cords in parts catalogs that are designed to be wired into the shore power connection by splicing, and
was just wondering. I haven't tried plugging the van in to the house yet. (I do have a 30 to 15 amp adapter plug for it)
Just thought I'd ask about this first.

Thanks for all the help.

[markopolo]

Originally Posted by Mike

.......................While we're on the electrical problem hunt, I noticed that my shore power cord looks "spliced" about 2 feet from the spot where it dissappears into the interior of the vehicle. Is that normal? ..........

I don't recall seeing something like that on my RT. It may have been repaired at some point or maybe the previous owner wanted a longer (or shorter) cord.

If it looks reasonably well done I wouldn't be concerned about it.

If you're getting the isolator replace maybe have the dealer take a quick look at it.

[Mike]

Thanks for the opinion. I may pull the electrical tape (bad sign maybe?) off the wires and have a
closer look. In the RV parts catalog, there were a couple of extension cords which came with
loose bare wire ends so that you could add/splice the extra length. The problem with my splice job
is that it's on the short 6-7 foot length of cord, not the 20 foot extension cord that I got with the van.
So I'm suspicious. I'll probably get a second opinion at a service centre.
Thanks.

Oh and I forgot the third additional problem discovered over the weekend of exploring the many onboard
systems of the Roadtrek.
The ONAN Microlite 2800 has started backfiring when I try to start it.
I'm afraid to keep trying as the noise and force of the backfires is pretty intense.
I admit I haven't been diligent in exercising it through the winter. Mea culpa.
Any ideas about it? I've seen everything from bad coil/low spark to low oil level
to gummed up carb. I added fuel stabilizer to the tank last November to prep it for inactivity,
and did fire up the generator for about a half hour to try to suck some into it.

All in all, not the results I was hoping for this weekend with the Roadtrek.

[markopolo]

Originally Posted by Mike

......................... The problem with my splice job is that it's on the short 6-7 foot length of cord, not the 20 foot extension cord that I got with the van...............

I think your van would have had a longer cord from the factory. Mine must have been 10' or more. Maybe send a quick email to service @ roadtrek.com and ask how long the cord would have been on your model year.

I can't help much re: the gen backfiring. If it was mine I'd remove the spark plug, clean it and set the gap. I'd also spray some carb cleaner into the carb.

Tough weekend Mike. You'll get these issues sorted out.

[Mike]

I'll try the email question.The cord just reaches from the rear end of the large storage compartment to the front.
So I'd guess it's about 6 feet long. Probably a pull away while still plugged in? Hard to believe, but possible I guess.
That was my first thought when I saw it.

I'm just looking for the VIN number. Roadtrek always hassle me for the VIN number when I email them.
Thanks for the moral support.

UPDATE: According to Peter at RT, the original power cord was 36 feet long with 7 feet "buried in the
vehicle" so a total external length of about 29 feet. He also suggested a previous owner may have either
damaged, or shortened it as a preference. I still have a 20 foot extension for it, so I think I'll put this one
to bed, for now.
I also mentioned that the 2 service dealers that I'd contacted hadn't got back to me in over 6 days.
He was sympathetic to their situation, in terms of staff reductions in the current economic
environment (paraphrasing), and suggested I contact them again, or wait a bit longer.
Hmmmmmm????

Thanks again.

[Mike]

Generator update: I tried it yesterday and it fired up first try. I tried it with the van's engine running.
I believe we've mentioned this scenario before in an exercise the generator thread on here somewhere.
That if you can't get it to go try it with the vehicle engine running. Seemed to make a difference for me
so I'm back burnering that one for now.I read on the internet somewhere that low spark might cause backfiring,
so I'm thinking the extra juice leaking through my faulty isolator might have made the difference.

Isolator update: I got replies from Mobilife in Kitchener, Ont. and even though I told them all the tests I've done
with suggestions from yourselves and John Slaughter (without mentioning names, of course), and the results
I've got, they still want me to "bring it in to properly diagnose the problem before quoting me a price on the
isolator replacement and part". So that's not working for me, and I replied to that effect. I said I'd think about it.
I also got a reply from SunnFunRV in Waterdown, Ont. quoting some labour costs at $88/hour (probably the
going rate) with some realistic projected repair times, but they quoted a price of $122 for a 120 amp replacement isolator.
I sent a follow up note mentioning that the OEM model was 130 amps, and asked what would happen if I installed
a lower amperage model. I have yet to hear back from them.

I've sent a note to Owasco in Oshawa Ont. with my isolator details and am waiting for a reply.


Roadtrek authorized service centres in Ontario don't seem too useful so far. Or am I being too picky?

[Ron J. Moore]

Mike, you mention the problems your having with the Onan and you mentioned that it doesn't get the exercise, etc.; I'd also recommend that you pick up at can of SeaFoam Gas Additive and put into about a half to three quarters of a tank and run the generator to clean out the carb. Ron

[VernM]

When my Honda 2000 generator doesn't want to start (usually from inattention for longer than I should), I have found a regular solution to be take off the air cleaner and give it a good chance to breathe while cranking. Works every time.

[Mike]

Hi Ron/VernM,
Mea culpa. I should run it more often, and put a load on it, too. I'll see if I can
find Seafoam gas additive up here in the Great White North. | did add fuel stabilizer to
a full tank last fall when it was going to sit for a while, and ran the genny for a while afterwards.
I wish it wasn't located under the rear of the van, it's hard for me to get to, to see what's
really happening when it has problems. let alone to remove the air cleaner, but if it starts acting
up again, I'll see if I can reach it.

Thanks for the comments.

[markopolo]

Originally Posted by Mike

...................... I got replies from Mobilife in Kitchener, Ont. and even though I told them all the tests I've done with suggestions from yourselves and John Slaughter (without mentioning names, of course), and the results
I've got, they still want me to "bring it in to properly diagnose the problem before quoting me a price on the
isolator replacement and part". ..............

I'd go to Mobilife just to see all the add-on cabinetry
Link: http://www.mobilife.on.ca/classb.html#accessories

Getting an RV repaired can be a nuisance. I can see them only being able to "ballpark" the proposed solution and cost over the phone. Looks like they prefer to give a quote only after seeing it and that is understandable also.

That's good news re: your genset. The trick of starting the van motor first works often.

[Mike]

Oddly enough they were sort of recommended by the service guy at Roadtrek, and they're the ones I'm
most disappointed with. Both the tech at Roadtrek service, and John Slaughter are pretty sure my isolator
is toast, based on my tests and results. It bothers me that Mobilife want to take an hour to tell me the same thing,
then charge me for the part, and no doubt another hour to install it. And no one has been able to offer me the
original part, or the Roadtrek authorized alternative replacement part (Hehr Powerline 33-301 is what they used as a replacement up until they went with a battery separator instead of an isolator). It is 150 amps and is acceptable
as a replacement part according to Peter Lange at Roadtrek. He suggested trying local RV and Marine supply shops
as he knows there aren't any RT repair facilities near me. Said it didn't have to be a RT shop, which I will try.
There's a few marine supply places around here.
SunnFunRV are trying to find one that's 130 amps or more. They're still looking.
Owasco had a 150 amp isolator, but they've been discontinued, so they suggested I try an automotive parts supply.
I finally got in touch with Hehr in Texas today and they have all the original and replacement parts, and will ship to me.
I may try that instead of dealing with the local experts. Or I may try the local marine and RV places although the nearest RV place only had smallish stuff (low amperage <or=120). I might see if they have a 150, as I thought it had to be 130 a week ago when I first checked there.
Roadtrek OEM isolators are hard to find.

My wife thinks I'm nuts for going to all this trouble, when we just need to remember not to leave the
battery disconnect enabled when not in use.
Maybe she's right.......

re genset: Oh yes ....... I think I'll always start the engine first from now on, whether it's recommended or not.

[markopolo]

If the isolator has failed and is allowing the vehicle battery to discharge then you could be off camping somewhere and find that when you want to leave you are not able to start the motor due to a flat battery.

A battery separator would be an upgrade. With it, you plug the van into grid power and both the house battery and the vehicle battery get charged. If you are camped with power hookup then you can use the van radio/CD player because the vehicle battery is being charged.

I'd go that route if the costs were similar.

It's good to know that Hehr will ship direct to end users.