Reply
 
Thread Tools Display Modes
 
Old 05-09-2009, 07:54 PM   #1
Platinum Member
 
Mike's Avatar
 
Join Date: Aug 2008
Location: Sarnialabad, The Newly Elected People's Republic of Canuckistan
Posts: 3,207
Default Battery Isolators - how long should they last?

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.
__________________

__________________
It's not a sprint(er) (unless you make it one), it's (hopefully) a marathon.
RV - 2018 Navion 24V + TV - 2016 JKU
Mike is offline   Reply With Quote
Old 05-10-2009, 02:05 AM   #2
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,305
Default Re: Battery Isolators - how long should they last?

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.
__________________

__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 05-10-2009, 12:11 PM   #3
Platinum Member
 
Mike's Avatar
 
Join Date: Aug 2008
Location: Sarnialabad, The Newly Elected People's Republic of Canuckistan
Posts: 3,207
Default Re: Battery Isolators - how long should they last?

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.
__________________
It's not a sprint(er) (unless you make it one), it's (hopefully) a marathon.
RV - 2018 Navion 24V + TV - 2016 JKU
Mike is offline   Reply With Quote
Old 05-10-2009, 03:11 PM   #4
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,305
Default Re: Battery Isolators - how long should they last?

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
__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 05-12-2009, 11:35 PM   #5
Platinum Member
 
Mike's Avatar
 
Join Date: Aug 2008
Location: Sarnialabad, The Newly Elected People's Republic of Canuckistan
Posts: 3,207
Default Re: Battery Isolators - how long should they last?

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.
__________________
It's not a sprint(er) (unless you make it one), it's (hopefully) a marathon.
RV - 2018 Navion 24V + TV - 2016 JKU
Mike is offline   Reply With Quote
Old 05-13-2009, 05:12 AM   #6
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,305
Default Re: Battery Isolators - how long should they last?

Quote:
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.

Quote:
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.

Quote:
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.

Quote:
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.
__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 05-13-2009, 05:26 AM   #7
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,305
Default Re: Battery Isolators - how long should they last?

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.

__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Old 05-13-2009, 02:10 PM   #8
Platinum Member
 
Mike's Avatar
 
Join Date: Aug 2008
Location: Sarnialabad, The Newly Elected People's Republic of Canuckistan
Posts: 3,207
Default Re: Battery Isolators - how long should they last?

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.
__________________
It's not a sprint(er) (unless you make it one), it's (hopefully) a marathon.
RV - 2018 Navion 24V + TV - 2016 JKU
Mike is offline   Reply With Quote
Old 05-24-2009, 04:06 PM   #9
Platinum Member
 
Mike's Avatar
 
Join Date: Aug 2008
Location: Sarnialabad, The Newly Elected People's Republic of Canuckistan
Posts: 3,207
Default Re: Battery Isolators - how long should they last?

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.
__________________
It's not a sprint(er) (unless you make it one), it's (hopefully) a marathon.
RV - 2018 Navion 24V + TV - 2016 JKU
Mike is offline   Reply With Quote
Old 05-25-2009, 03:47 AM   #10
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 7,305
Default Re: Battery Isolators - how long should they last?

Quote:
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.
__________________

__________________
Two bikes on sliding cargo box: https://www.classbforum.com/forums/m...icture206.html & 1997 GMC Savana 6.5L Turbo Diesel Custom Camper Van Specifications: https://www.classbforum.com/forums/f...vana-5864.html
markopolo is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 05:46 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2018, vBulletin Solutions, Inc.