Dual Batt. Isolator in Diesel

Post by **coxy321** » Sat Jan 19, 2008 12:33 pm

Hi all. I'm looking for a dual battery controller for my TD42, and i wouldn't mind sticking with the "old school" dual battery isolator, which i have had no hassles with in the past.

My problem is that i've got no idea where i can pick up power to activate the solenoid while the engine is running. I want the solenoid bridged only while the engine is running. I was thinking of using the oil pressure sensor, but i'm told that its setup as normally closed (with engine off) so that wont work as a switch.

Any of you guys got any idea as to where i can pick up 12v only while the engine is running?? Maybe off the itic motor for the injector pump or off the back of the alternator's exciter circuit??

Cheers - Coxy

Post by **Thylacine** » Sat Jan 19, 2008 4:07 pm

Use the oil-pressure switch to call a NC relay connected in series between your battery and solenoid switch-wire.

ed

Post by **BOGAN V8** » Sat Jan 19, 2008 10:29 pm

You can use the wiper motor on some cars just have to check which wire has power when the car is running and not when the car is turned off

Post by **Thylacine** » Sun Jan 20, 2008 2:41 am

When using power from "accessories" as soon as you turn the key your batteries are linked. Not real flash for starting if your auxiliary is low.
Using oil-pressure is preferable as it ensures that the car starts from the main battery every time.

ed

Post by **familybus** » Sun Jan 20, 2008 8:03 am

save yourself the added hasle and get a REDARC of Ebay and set that up! easy to do and so far in my GU its been reliable for 2 years!

Post by **BOGAN V8** » Sun Jan 20, 2008 9:55 am

Most cars that we find dont have power at the wiper motor with ACC on but when you turn the key to start the power goes away but comes back when the key is returned to igntion....

Post by **coxy321** » Sun Jan 20, 2008 8:08 pm

Might go the naturally closed relay off the oil pressure switch, so it runs 12v with engine oil pressure (didn't think of that one!).

I've got 3 new isolators sitting in a draw in my garage - so no point wasting any $$$. And i'll give the ACC power a miss, as it relies on ME remembering to turn the ignition off- not likely!!

Cheers!!!

Post by **HotFourOk** » Mon Jan 21, 2008 7:44 am

Thylacine wrote:When using power from "accessories" as soon as you turn the key your batteries are linked. Not real flash for starting if your auxiliary is low.
Using oil-pressure is preferable as it ensures that the car starts from the main battery every time.

ed

As Bogan said, most cars have the wipers switched at the 'ON' position, not accessories, and power is cut during starting.

Does the oil pressure switch power come on when the pressure builds up?

Post by **coxy321** » Mon Jan 21, 2008 7:57 am

I'm 99% sure that its a naturally closed setup, so when you start the motor (and your oil warning light is on), it build up the oil presure, the switch then opens, and turns the oil pressure light off. At least thats been the case in most cars i've owned. I'll head out tonight and put a multimeter on it to check.

I'll throw the test light onto the wiper motor harness too while i'm there.

Coxy

Post by **Loanrangie** » Mon Jan 21, 2008 5:41 pm

Injector pump solenoid is an easy pickup point.

Post by **lexi** » Tue Jan 22, 2008 8:41 am

Alternator charge indicator wire. Feed it to a relay then solenoid. It will connect batterys when you rev engine and disconnect when engine stops.

Alex

Post by **coxy321** » Tue Jan 22, 2008 10:33 am

I had a look, and i'm pretty sure that the charge signal wire still has a very small output voltage with the engine not running, maybe 3-6v.

Coxy

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Dual Batt. Isolator in Diesel

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