Duel Batt solenoid

Our local auto electrician has installed about 100 voltage sensitive relays in fourbys in the south west of Vic. they have been very happy with them, no problems of spikes to speak of. they can handle 90 amps, turn on at 12.8 volts and out again if it goes over about 14.8. It was about $80.
nickR

And you think your local sparky would know - what a worry.
It is most definitely not OK to use solenoids without protection on modern vehicles. Considering you can buy a proper battery isolator system like a Redarc with proper protection for $125.00 why would people be so stupid as to fit something on hearsay from a local sparky.
I just love these posts that give not only totally incorrect advice, but advice that could result in damage to vehicles that could cost thousands of dollars.

This is for Feret.

ALANCO in Perth sell REDARC solenoids. I got mine through work at trade price, however retail ~ $125 as mentioned above.

Hugh

Ferret,
Your Auto Sparky, I assume is licensed, he had to sit examinations etc...
And he also had to pass them… so he is qualified to give you advice!

You have ask him his opinion and he gives you an answer you don't like, and ask the same question on the forum and place your trust in the replies received from people that may not have a "certificate of competency in Auto Electrics".
However, some do have motives such as the desire to sell you a redarc isolator.....

FACT IS; Redarc specify in the centre of their own solenoid specifications sheet in BOLD their solenoid should only be used with two identical batteries… undisputable fact.

#Do you know why Redarc prints that warning there ???
#What is it Redarc know, that guys flogging them don’t want you to know ???
#Should we believe Redarc print the warning there for no reason at all ???

If you are using two identical batteries then buy redarc in place of the qualified advice of your sparky, if you have two different batteries consider this; what gives someone on a forum selling redarc isolators the right to tell the isolator manufacturer their own tech specifications are wrong ? ? ?

I have asked Redarc to explain to me 'in writing', why they print the warning there in the centre of the page and in bold, to date no will do, just say some people have them connected with two different batteries…
and send me a catalogue.

just my thoughts, and I have no connection to anything electrikaal.

Hi,

There are 2 issues. If you use an ordinary solenoid that just parallels the batteries, there will be a voltage spike from the solenoid coil whenever it is de-energized. This may or may not damage the computer over a period of time.
The computers are obviously protected in some way and it may never happen. A simple precaution is to connect a diode across the coil. Some solenoids already have this.
If you use 2 different batteries, i.e. a normal starting battery and a deep cycle one, there will be problems when the deep cycle one is discharged. As the solenoid (or relay) closes, it will apply the full voltage to the deep cycle battery and will charge it at a very high rate, which is something that should be avoided as it will severely shorten the service life of the deep cycle battery.
Some, but not all battery controllers have current limiting to avoid this probblem.

Cheers

Only problem with your theory is that a Deep Cycle wet lead acid battery has a higher internal resistance than a starter battery and will not draw anywhere near the current a starter battery will.
Most will only draw a few amps even after being heavily discharged.
You will certainly not require any current limiting for a conventional wet lead acid deep cycle battery.
Most AGM batteries and GEL batteries are another story, they can draw anywhere up to 75% of their A/H rating whilst charging.

Do a google search on TRAXIDE. This is the only isolator around that will keep the batteried connected in parallel until their combined voltage drops to 12.0V (still enough to start the car on one battery) - adding quite a bit of "free" power into the system. Australian made - and the owner is happy to work with you. No affiliations either, and my car has an ARB unit (fitted by the dealer)!

Cheers
Andrew

Oops. I stated GEL starting battery, and this is absolutely wrong!!!!!

I should have typed CALCIUM starting battery.

Sorry about that.

Cheers

Muzz

Hi Scott,

Per your other question re contact details for Alanco who supply Redarc solenoids, amongst many other electrical needs.

Alanco Automotive Products
83-85 Welshpool Rd
Welshpool, WA
9458 1300
www.alanco.com.au

Regards,
Hugh