smart solonoid

Submitted: Friday, Jan 16, 2004 at 07:38

ThreadID: 9788 Views:1572 Replies:6 FollowUps:6

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tim

Hi All
I am cuurently installing a smart solonoid into my 2002 3.0 tdi patrol
I want to install a manual switching switch on my dash but i am not sure what the 3 spade lugs are for. I Know the bottom one is too earth,the middle one is meant to go to starting wire under steering coloumn. How do i connect a manual switch in to this and too which lugs do i connect too.
Should i leave the wire from the ignition connected or disconnected
Thanks all
Tim

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Reply By: Notso - Friday, Jan 16, 2004 at 09:40

Reply By: Outnabout David (SA) - Friday, Jan 16, 2004 at 11:28

Reply By: Mark - Friday, Jan 16, 2004 at 12:30

Friday, Jan 16, 2004 at 12:30

I have just finished installing a smart solenoid into my 2003 3.0TD. Its the Redarc one, not the ARB, but apart form the sticker its identical (and the price - $99 from coventrys at trade !!!).

I wired my slightly differently to the standard method. I did not connect the two battery + terminals to the solenoid. Instead, I connected the alternator directly to the solenoid terminal with a heavy (starter) gauge wire, with the other solenoid terminal connected to the second battery.

The upside of this is that the second battery can be charged at max alternator output, unlike the restricted output when charging by the main battery. This significantly decreases the charging time for the battery, and also noteably improves battery life (battery fully charged - not 1/2 charged then flattened again, espeically when limited running of vehicle)

The downside is that you cannot use a switch on the solenoid to "jumpstart" a flat main battery. The reason for this is that the wire from the alternator to the main battery will have to carry the full starting current, and it is NOT designed for this.

However, by simply carrying a single jumper cable you can connect the second battery positive to the "flat" main battery positive and jumpstart. Its only a bit more effort, but how often are you goingto have a flat main battery???

If interested, I can send pics of the installation showing how the wiring was done etc...

Cheers

Mark

AnswerID: 43222

Follow Up By: Member - DOZER- Friday, Jan 16, 2004 at 20:48

Friday, Jan 16, 2004 at 20:48

Mark Be vary careful man....a flat main and a jumper lead will fry your computer, it will spike it at the very least.
Also if you have a flat aux and the solenoid joins the two batteries via the alt, there will be a rush of volts down the wrong way from the main to the aux to equalise them, and the factory wiring between the alt and main might not like it.
3rdly, the problem is that with a flat aux and a full main, the alt sences the full main (as it is wired up to service the main) and the flat aux gets a trickle charge once its surface charged (once it reaches 13v from 11) which only takes a minute BTW.
Andrew
wheredayathinkwer mike?

FollowupID: 305578

Follow Up By: Mark - Saturday, Jan 17, 2004 at 02:47

Saturday, Jan 17, 2004 at 02:47

Dozer, yeah you need to use a surge protected jumper, I agree.

But the flat aux to full main, there is a surge form the main to the aux when it connects. The alternator can supply say 90 amps on initial connection plus whatever from the main battery. As you say, there is that initial surge, but the wiring should be rated to at least what the alternator can supply. Thus there is now say 180 amps available to charge the flat aux.

But there is no way you can pump that sort of amps into a lead acid battery hence the main battery will not actually supply anywhere near 90 amps, the batteries internal resistance is way too high.

If one is conncerned about this "reverse" flow, then you can easily install another connection from the main battery to the solenoid in addition to the one from the alternator. But IMHO this is not necessary.

The advantage of direct connection from the alternator to the solenoid is the ability to actual use the full output of the alternator. While the factory wiring may handle 90 amps, there is a voltage drop due to the smaller size wire compared to the new wire installed to the isolator (note - one defeats the purpose if only a small guage wire is used form the alternator to the solenoid). Even a small voltage drop makes a notable difference to battery recharge rates.

As for alternator sensing, when both batteries are commoned and the aux battery is relatively flat, the charge equalisation (as both are connected they must be at the same voltage) lets the alternator charge at a higher rate. But there is a significant difference in amps sent to each battery due to the different internal resistance of each battery.

But the point you raised about the rush of volts is valid if a gel cell type battery is used. They have very low internal resistance and this is why they can recharge so quick (high input amps).

Ideally, the rotronics type of isolator is superior as it directly connects the alternator to a single battery at a time. This stops the charge equalistion and allows maximum battery recharge. However, the cost of the complete kit is IMHO too much for its advantges.

Cheers

Mark