My crank battery wouldnt hold charge in my dual-battery system so...

yep, the chage wire is usually connected to the batt but it seems it would not matter if the charge wire was attached at the positive end of the solenoid, its directly connected to the battery from there anyway??

orrrrr - does this matter//

When the vehicle is brand new the Alternator sends the 12v current direct to the Cranking battery via a thick black cable.

You or a previous owner, then fits a second battery and a Solenoid which is then connected between the two (+) pos battery terminals.

or have I misinterpreted your post ?

you posted "could not quite figure out how the regulator controlling the input into my 2nd battery would be affecting my cranking battery - but who can tell??"

is it because the crank battery accesorys wire maintanins a small charge to maintain the charge required to keep the solenoid switched to the second batt?

this is the only thing I can think of in an otherwise sound logic system...

pls keep postin'

hmmmm - havbnt tried taking my key completely out.... hmmmmm bluddy-hell, anudder battery to be cooked...lol....

ive dissconnected the crank batt tested it and the fridge batt switchs on and off with the ignition going from crank to aux... it does isolate the crank battery from running the fridge but not the lights it seems....

heya Max, many thanks for your post. Ive decommisioned the solenoid and fridge and everything runs good...

i am next to connect the charge wire back to the aux battery and continue runnig the fridge direct off it untilll the fridge cuts it at 11volts.. yes, this will eventually kkill the aux batt but the cost is one thing, whereas knoledge is priceless...

lol... knowledge is priceless

Robert - Cutting out the fridge at 11 volts should not kill the aux battery, as the cut out switch is designed to prevent that happening. For the overnight test it may pay to take the lead off the main battery to make sure it is not still connected somehow to the auxiliary.

The next thing is to start to check voltages. If you don't have a multi meter, you can get a perfectly ok one for about $10 at Bunnings. Figure out how to set it on DC volts, and it would be interesting to do a series of readings of voltage on each battery (across the terminals) at various times, such as:

1. Just before starting it in the morning - cranking battery should be 12 volts or so, auxiliary something over 11 volts.

2. Immediately after starting - cranking should go quickly to about 14 volts, the auxiliary should stay at the same as before starting till the solenoid switches in.

3. Once the cranking battery is charged up the solenoid should cut in (if it is an automatic one), and the terminals at the auxiliary come up to the same as the cranking battery. (For this to happen you may need a fast idle, as diesels especially don't charge at idle revs).

If as Sandman suggested your solenoid is manually switched, or if it is an automatic one and not working, you would get the same voltages on each battery all the time, and that could direct the next lines of enquiry.

Good luck
Max

heya Max, thanks for the replys....

ive disconnected the solenoid and second battery completely...

1. crank batt read 11.75v (used the cabin lights the night before
2. Immediatly after starting got a reading of 13.36v
3. 3 hours after many-stops-starts 12.21v

I been knocking my head on this for a while - i know if i connect it all back up my blommin crank battery will flatten overnight...

when it is connected the aux battery definetly supplies power to the fridge but not to the cabin lights, is that right?... i thought all the acces were supposed to be isolated...

3. 3 hours after many-stops-starts 12.21v

i meant after 3 housrs parked from a day of many stopstarts....

Hi Robert

Definitely the crank battery is charging and running ok.

The cabin lights are, I presume, the ones that the vehicle manufacturer put in long before there was an auxiliary battery, and should be off the main battery. You can usually turn them off - I only use them when the passengers need a bit of light.

The auxiliary battery should have its own fuse(s) and circuits to non OEM accessories like the fridge, winch etc.

I am assuming that yours is an ordinary 4x4, not a Motorhome. Am I right there? (If its a motorhome or camper, then the extra cabin lights must not run off the main battery).

If it is a normal 4x4, I reckon you need to try to figure out if the solenoid is isolating the auxiliary battery from the cranking battery when the engine is off.The best way to do that is to shove the positive lead from the solenoid to the auxiliary in a sock so it does not short on the car body, then hook up the solenoid. Stick the red lead of the multimeter on to the positive lead in the sock, and the black on a good earth point. It should register zero when the engine is off.

Start the engine, and after a very short time, the reading should be the 13.3 or so of the main battery.

Turn off the engine and the reading should be zero again.

If not, your solenoid is not isolating the batteries.

Questions then:

1. The leads to the two little terminals on the solenoid need checking. One should go to earth, and the other to either a switch on the dash (if its manual) or to a point which is only alive when the engine is running. Trace them out and see.

2. You should also be able to check the two little leads by checking voltage between them - zero when the engine is off and 12 volts plus or minus a bit when it is running.

Try all that and hopefully you will be close to solving the problem.
Happy hunting
Max

thanks again Max...

It is an old L300 4x4 van and before the rest of you start to snigger Ive got seven out of eight passes over Ngala rocks, Fraser Island...

anyway Max, being a van it is difficult to check stuff and I am out bush ATM with a injured hip making it even more difficult, but I'm still at it.. back in a day or so, I have to remove the seats & fridge to get to everything...

robertbruce posted:

""after 3 hours parked from a day of many stop-starts.... 12.21v""

The Crank battery is either not being charged correctly or not holding it's charge, as it should be 12.6v minimum, not 12.2v.

The number of stop starts is not relevant because the Cranking battery will reach 14 plus Volts with-in a few minutes of starting and then maintain ~12.6 Volts after a few hours if not faulty.

Robert -unfortunately you aren't going to make any progress until you check out the solenoid as per my post above. My guess is that it is not isolating the two batteries and overnight it is running the crank battery down, then during the day you are not doing enough driving to get the crank battery up to voltage on its own before taking the second battery & fridge load.

Seeing your hip is giving you a hard time, all you can do is nurse the batteries by taking the globes out of the cabin lights, and maybe turning the fridge down to the minimum setting then get it all checked out when you get back home.

Great to hear that there are still Starwagons running - they always were very nimble off road.

Good luck
Max