Dual Battery system problem

Submitted: Sunday, Apr 11, 2010 at 10:34
ThreadID: 77632 Views:2800 Replies:3 FollowUps:5
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We have a dual battery system consisting of a 150Ahr deep cycle battery in the
back of the car, and a 80 AHr cranking battery under the bonnett and a 100Ahr
deep cycle battery in the camper with a 140Amp isolator under the bonnett and a
100 Amp circuit breaker between the isolator and the batter in the back of the
car.

On a recent trip everything was working fine until day 6, and after a day of sand driving, when the fridge in the
back of the car showed the temp rising. The problem seemed to be with the
battery in the back of the car. Took it for a drive and it was ok, but after a
few days, charge didn't hold for long.

After we got home further investigation showed that the isolator under the
bonnett was switching off and on rapidly, so we disconnected the earth and
reconnnected it, and now it doesn't go off so the two batteries are connected
constantly.

Any advice as to where to go now? Does it sound like we need a new isolator?

Please be patient - I'm only the computer operator translating for hubby. Thanks in advance.

Jeannie and Doug
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Reply By: Member - Captain (WA) - Sunday, Apr 11, 2010 at 10:45

Sunday, Apr 11, 2010 at 10:45
Yep, certainly sounds like the isolator. What type is your current one?

Cheers

Captain
Its not what you drive, but how you drive it!
LC 200 + AOR Quantum

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Classifieds: AGM battery 120 a.hr (2 available)

AnswerID: 412495

Follow Up By: Shaker - Sunday, Apr 11, 2010 at 10:50

Sunday, Apr 11, 2010 at 10:50
It sounds like it may be a VSR, in which case I would get the batteries tested.
Mine did the same thing on a recent CSR trip, it proved to be a battery issue.
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FollowupID: 682525

Follow Up By: Member - Magic (VIC) - Sunday, Apr 11, 2010 at 10:50

Sunday, Apr 11, 2010 at 10:50
Hi Captain

It's a BEP Marine Ltd VSR (Voltage Sensitive Relay Module) - it was fitted by a friend who's an auto electrician when we were getting our camper trailer. We've since fitted the battery in the back of the ute.

Cheers

Jeannie
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FollowupID: 682526

Follow Up By: Shaker - Sunday, Apr 11, 2010 at 11:20

Sunday, Apr 11, 2010 at 11:20
Same VSR as mine, mine was a battery problem, I can't tell you which one as they both packed up together!
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FollowupID: 682532

Follow Up By: Member - Magic (VIC) - Sunday, Apr 11, 2010 at 11:26

Sunday, Apr 11, 2010 at 11:26
Thanks Shaker

Hubby's off to get the batteries tested now.

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FollowupID: 682535

Reply By: Steve and Viv - Sunday, Apr 11, 2010 at 11:30

Sunday, Apr 11, 2010 at 11:30
if you test the batteries do they bot seem to hold a charge. One could be failing causing the sensor to think it needs to isolate the main battery but in the next second it sensors an OK voltage but then the main battery drags it down again giving you a on/off situation. If, with the engine running you put a multi tester on the main battery do you see a change in voltage? It may pay to pop to your local battery place and get a load test done on the battery then move to the isolator as a fault after that. It's hard to tell for here but it could be both
AnswerID: 412506

Reply By: ABR - SIDEWINDER - Sunday, Apr 11, 2010 at 21:22

Sunday, Apr 11, 2010 at 21:22
Hi Jeannie and Doug

Have the auto electrician test the alternator output too, perhaps it is very close to the VSR threshold.

Another main cause of VSR cycling is using too thin cable between the main battery and the VSR. This causes a voltage drop under load and the VSR switches off again.

If you discharge your aux battery too low this will also cause a large voltage drop as the VSR switches on and it may start to cycle until the voltage equalizes.

Regards

Derek from ABR
AnswerID: 412585

Follow Up By: Racey - Monday, Apr 12, 2010 at 09:36

Monday, Apr 12, 2010 at 09:36
If you have a series 100 cruiser you may need to get a different relay. I believe they have a different output voltage and require a different sensing voltage. I mate of mine installed a Redarc unit which is mainly for the S100 Redarc have 2 variants with different sensing models. Sorry I can't remember the details. It would fit in with Derek's comments.

Cheers
Racey
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FollowupID: 682664

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