Thread: Beware Charging Dual Battery in D4.

Hi Phil
I was hoping that in amongst all it might have shown the garbox and engine temp, would be handy if it did.

BarryH

Thanks to Phil doing a hell of a lot of driving yesterday, a lot more accurate info is now known about D4 voltage operations and Phil’s D4 operations with and without the SC80-LR connected.

In short, the addition of an SC80 dual battery system has no effect on the operation of the D4’s electrics.

The good thing is that thanks to Phil and quite a bit of feedback from other D4 owners, it now seems clear that the SC80-LR not only performs flawlessly with the D4, but it now appears that the SC80-LR is the ONLY dual battery isolator that will work properly in a D4.

Phil and I spent hours driving around, testing the D4 system with and without the SC80-LR connected and no matter what situation we put Phil’s D4 through, there was absolutely no difference in the operation of the D4’s electrics, and more specifically, the voltage levels, whether the SC80-LR, with an auxiliary battery, was connected or not, the D4’s voltage response was exactly the same.

Also now confirmed, again thanks to Phil’s assistance, that the way a standard SC80-LR operates, means that the auxiliary/house batteries are going to get a good sustained charge, whereas every other isolator that I am aware of will continually cut in and out, if they manage to cut in at all, and this is going to be an even bigger problem with DC-DC converters.

Recently returned from 3 weeks/7000km of travel in my D4 with a Traxide SC80 DBS and a 2nd battery (Optima D34) in the rear for the fridge.

Installation was as Tim has described (about 2-3 hours, taking my time), and the setup worked flawlessly.

Certainly pleased I went with the Traxide setup and self-installation instead of the $1500 quote given to me by a retailer for them to do a similar setup with another product.

Hey Ipanena, with the installation did you find all the cables were run to the back of the car as described? I had a quick look in the back of mine and wasn't sure they are there?

Michael

Hi Michael,

The cable to be run to the back is a heavy gauge (6mm?) dual cable which goes through the firewall near the accelerator pedal, underneath the kick board/door trim, under the base of the B-pillar, and under the internal trim in the back to the hatch for the jack. I've installed a pair of of oulets on the right, opposite the factory one on the left. If I were to do it again, though, I'd probably install one of them facing downward in the recess in front of the jack access, to keep my fridge plug a bit out of the way. Will probably do this anyway when I get time. Picked up a (cheap) hole saw kit at Bunnings before tackling the the big step of nervously DRILLING INTO my beloved vehicle!

The Anderson plug for the second battery tucks away behind the trim, or can be brought out under it when in use.

Regarding threading the cable through the small hole in the firewall, a paperclip strightened out and then formed into a small hook was passed from inside the cabin to the engine bay, and hooked with a straigtened out coat hanger shaped to form a small hook. I had string tied to the paperclip, and was then able to draw the heavy gauge cable through quite easily.

The other internals all came apart and went back together exactly as Tim describes in his comprehesive instructions for non-mechanics and non-electrical engineers like me!

Hi All,

I’ve just returned from a 3 week 6,500K trip in the D4 3.0. I learnt some more info on the trip. As from previous posts I have a DC to DC charger installed to charge up 2 x 60 AH batteries. I was having some problems with the voltage in the D4 dropping below 12.7 resulting in the DC to DC charger not charging up the batteries.

This got worse on the trip. On several occasions and particularly while cruising in flat country at over 100KMH the voltage on the diagnostic screen would sit at 12.1V!! The car seemed quite happy to sit at that voltage. Take the foot of the accelerator and coast for a while and it would pop up to 13.7 for a little while but as soon as I resumed cruising it would drop back to 12.1V. Things were getting desperate as my second batteries were now not charging which could have resulted in warm beer!

I then remembered seeing another post about connecting accessories to the D4. Something about the car measuring total current draw by some device between the negative battery terminal and the earth on the car.

The DC to DC charger was connected directly to the positive and negative terminals of the battery. I then moved the negative connection of the DC to DC charger to a good earth point. This changed everything. The car then steadily ran at 13.7V while cruising. It still varied up and down between 12.7 and 14.2. Now the DC to DC charger happily charged the second batteries at 20 Amps up to 15.2V and then cycled down to a 13.1V trickle charge. No more problems!

A DC to DC charger is an option but must be wired up as described. Positive to battery and negative to earth.

The advantage of the DC to DC charger is that you get a full charge in the second batteries and that it will not let your main battery drain below 12.7V. Charging is also independent of the voltage that the D4 may decide to charge up to, which seems to be somewhere around 13.7V.

The disadvantages are the cost (about $500) and the initial charge rate may not be as fast as batteries connected through an isolator (although I’m not sure if more that 20amps is good for a battery anyway?).

Whichever type of charger you use I would suggest that you wire the negative to earth rather than the negative battery terminal.

Peter

Originally Posted by RoverLander

Hi All,
Whichever type of charger you use I would suggest that you wire the negative to earth rather than the negative battery terminal.

Peter, great to see that you found, what turns out to be, a simple solution.

I'm guessing that this advice also applies not only to battery chargers/isolators, but also to all other accessories. Such as driving lights and winches.
Perhaps some of the forum's illustrious auto electrickery engineers could comment?

Having been advised by peope on this forum who work at dealerships never to use the battery negative terminal for jump-starting due to the battery monitor attached to it, I am not surprised that an auxilliary battery controller or charger connected to that terminal will not function as expected.

In the same vein, I have never seen why one would want to have a wire connection between the cranking battery negative terminal and an auxilliary battery negative terminal when the best method is to use the body as the earth path, made mandatory on the D4.