Thread: DC-DC charger- which one?

Hi again Mijango, is that the cranking or auxiliary battery.

In either case, when you are not going to be driving for a a day or so, give the battery a good charge with your ctek then let it sit over night and see if it still looses charge.

To answer the original question.....

Its the low voltage version of the Redarc you need. It has an extra wire which you connect to a 12v source that comes on only when the motor is running. Once that wire becomes active the redarc unit knows it can start charging your battery.

If the car decides at some stage to run at 12.2 volts for some time (Which it is designed to do once the main battery has been fully charged) then the LV version of the Redarc will keep charging. The non LV version would stop charging below 12.7v.

The other main thing to remember is to connect the negative of the redarc to the body bolts near the battery. Do not connect to the negative battery terminal.

Ideally your camper trailer should run its own DC/DC charger for its battery.

I have this setup in my MY15 D4 and caravan. In this configuration the car battery management systems and second battery systems are completely separated and cant cause any issues. The car only sees an extra current draw.

Yes all this may cost more and it may take slightly longer to charge your second batteries at times. However they will be fully charged independent of what the car systems a doing.

Peter

Hi Peter and your D4 should never operate at 12.2v.

At that voltage level, you would be running so low that you would be discharging your cranking battery while driving, and it is this error low voltage that has been causing problems that requires a software upgrade.

There was only one make of vehicle that ran at that sort of voltage level and that was the Ford Ranger. It caused so many related and unrelated problems that anyone with a Ford Ranger can now have the variable operating voltage program deleted by the Ford dealers. They then run at a constant 14+v.

While a D4 has a very large alternator capable of powering a couple of DC/DC devices, DC/DC devices still pull in huge amounts of current above the much smaller current they provide for the battery they are charging.

This adds an additional fuel cost to the operation of the D4, all for no gain.

Originally Posted by drivesafe

Hi Vern, the GU and the 100 have exactly the same charging setup and voltages

That was all I needed to know, dave could have just said that
I wired the 100 series, arb did the gu

Hi Vern and Dave was just trying to point out where the problem is likely to be.

The quickest way to start to check for a wiring problem is, while the batteries in the camper are low, and the tow vehicle's motor is running, measure for the voltage drop in the positive and negative circuits.

To do this simply run a length of thin wire from your cranking battery's positive ( + ) to somewhere close to the camper battery's positive ( + ) terminals and then use your multi meter to measure the voltage difference between the two positive ( + ) terminals.

Then do the same with the negative circuit. Move your thin wire to the cranking battery's Negative ( - ) terminal then go to the camper batteries and measure the voltage difference at the camper batteries Negative ( - ) terminals.

If all is well, then there should be a similar voltage difference on each circuit and the total voltage difference will give an idea in the cabling is too thin.

If there is a much bigger difference in one circuit compered to the other, you have probably found the problem and then have to find the specific cause.

The most common cause of poor battery charging is first, the use of cabling that is too thin, the next most common cause is a bad earth return and in most of these cases, it is because the chassis has been used as the earth return.

From memory tim, the camper batteries were .1v different to the alt output voltage when running. Will re test it all one day.

In all the years I've had the Traxide systems in our cars, we've never had an issue, now 3 vehicles so far and in all 3 vehicals the Traxide system has not only charged the auxillary battery, but prolonged the life of the OEM battery, I got almost 6yrs out of the OEM battery in the D2(2 weeks shy of 6yrs) now 4yrs from the OEM battery in the D4, so when Tim developed one for the Amarok, we got one, so it's coming up to 10yrs now, July/August 2005 to now, not an issue.

Baz.

Hi again Vern, I would actually expect to see a much larger voltage drop if the batteries were in a low or even just in a partially discharged state.

I carried out some tests in a D4, using a very low Optima D34 discharged down to 20% ( 11.58v ), connected to the alternator via a 10m length of 6B&S twin ( 13.5mm2 x 2 ) cable and at the beginning of the charge, the voltage drop was well over 1.0v but the battery was drawing up to 63 amps for a short time.

So again, if your batteries are low or just in a partially discharged state, there should be a larger voltage drop.

If you get a chance to test them again, let us know what you find.