Thread: D1 Duel battery setups

Hi I have just fitted a second battery to my D2 but had to put it in the rear, due to the size of the battery and lack of space under the bonnet. It works well for me as I can remove the battery and take it into the tent for lighting and the fridge.

I used an electronic unit simple to fit and so far very reliable, as well I have wired in circuit breakers in case something goes wrong. Will send a few pics and more details if you want to go in a simular direction
Andrew

If your going to put in a duel battery do your self a favour and make sure it has the same crank as your primary battery. two reasons first you can jump start yourself (very handy) second you can cycle your batteries.

I have succesfully done this for years, especially the self jump start very handy!!!

Gazz

Hey mate,

I upgraded the Dual Battery system which was in my 300Tdi a couple of weeks ago.

The car was purchased about 3 months ago with the second battery already installed and a simple manual cylinder solenoid.

I used to work for a battery distributor here in Perth and whilst working there also was trained to install Dual Battery systems.

Please note that I do appreciate that there are many different ways the people prefer to set up their dual batteries and I am in no way saying that this system is better or worse than any others which I have seen or had to install. This is the system I have used for years now and it is yet to fail me. The system is electronically isolated, uses a DC-DC converter on the AUX line to provide the AUX battery a more dedicated form of recharging than simply relying on the alternator (explained below). Note that my system does not use 2 batteries to start, to overcome a flat or faulty start battery requires a jumper lead to be run from the positive of the aux battery to the start battery, this can be overcome by using another solenoid but the situation should not happen too many times for me at the moment to warrant that just yet.

I have selected the batteries in the car based on the following factors:

I want to run an engle when I head out bush for a couple of days, however I also wanted a battery that could be used for starting in the event that the primary battery dies so I chose a Hybrid battery that is capable of being cycled but also can handle being used to start the car.

The main battery is also a hybrid but is primarily used for starting.

Batteries are as follows:

Main: ACDELCO S80D26R; 600CCA, 70A/H, 130RC [hybrid starting & deep cycle]
AUX: DELKOR M27; 570 CCA, 80 A/H, 145RC [hybrid start & deep cycle]
Isolator: REDARC SBI12, Electronic Dual Battery Isolator
DC-DC Converter: Electro Parts Australia Power Booster PB1120 20 AMP (Electro Parts Pty Ltd - Power Conversion, Automotive Electrical, Solar Power)

I am using an electronic isolator to get around a common problem with dual battery setups with a cylinder, continuous use solenoid (bottom of: http://electroparts.com.au/page.php?x=21). The problem with these solenoids is that they use the ignition key switch to switchover, meaning that as soon as the ignition key is turned on, the batteries are both in the circuit, if the primary battery drops a cell or fails the second battery which is brought into the circuit as soon as the key is turned, takes over starting the car. When the second battery fails eventually, you are left with 2 dead batteries.

The electronic isolator has a voltage sensitive relay and will not engage the second battery until the starter battery has recharged to 13.8 volts. Once this volatge is reached, the aux battery is brought into the system to begin charging. This presents a second problem.

Because the Alternator is connected to the starting battery directly (in most cases), Once the starting battery gets back to full charge after recovering from the engine start, the alternator will drop the amps down and will only deliver a trickle charge. This trickle charge is also passed to the AUX battery, meaning that the AUX does not get the full brunt of the alternator only a trickle charge, as anything more would overcharge the start battery. To get around this I am using the DC-DC converter. The converter will take a small amount of voltage (2V I think) off of the starting battery (voltage which is compensated for by the alternator) and converts this voltage into a maximum (for this converter model) 20 Amp Output charge. This means that the AUX battery gets an exclusive potential 20 amps to recharge with, as the charge in the battery increases, the resistance will also increase and lowers the 20A charge down to a trickle charge.

More info on this device can be found on the link I attached above.

Some pics of the setup:



Above: Starting Battery (Redarc isolator at the top of the photo)





Above: The Aux Battery (being a tdi the only component that had to be moved was the Power steering resovior, I think the V8 models need to have the coil and ignition module moved as well as the Power Steer Res.) It is a tight squeeze, however the air cleaner is about 2 millimetres clear of the battery.



Above: The new location for the Power Steering Res, The previous owner has had to make a custom Bracket for this and also get longer hoses to satisfy the new distance to the steering box.



Above: The electronic Isolator side mounted on the drivers side of the engine bay. The aux cable is going off to the left and the primary to the right. The aux cable goes through the firewall and down the console to the Power Booster.



Above: The 20 Amp Power Booster (input side) with the on/off switch. (allows you to turn the dual battery system off in the event that the start battery goes flat).




Above: Power Booster information Plate. (Note that the booster does heat up when under heavy load and has a thermal sensitive fan which automatically self engages and disengages to control the temperature.)



Above: Output for the booster, showing the 12V connection to the start battery (Power On) 12V connection to the Aux (Stand By) Battery Low and Overload light (which will illuminate when there is a full 20 Amps being delivered to the AUX.)

The system does NOT require a power booster to function, this is simply an extra part you can install optionally, you can simply run the positive cable from from the start battery to the primary on isolator, then run the auxillery from the isolator to the Aux battery this will mean that the system engages after the start battery reaches full charge and use the alternator to charge both batteries.

As the setup I am using has the capacity to only use 20amps, I have used 8 B&S Cable which is rated to 50 amps and have used a 30 amp fuse on the positive of the aux line.

Hope this helps

Totthead

Presuming you have fitted a snorkel that removes the air intake tube from front of the air cleaner it's simple.

1. Get a battery that will fit in the space without shifting the power sterring reservoir. This is the same size as the normal battery. An Exide Extreme N50 or similar will do nicely. About $170 and a good all purpose battery.
2. Clamp it down with a clamp from Supercheep or wherever.
3. Order a Traxide SC40 and mount it on the side panel near your main battery.
4. Run 6 mm twin black/red wires between main battery and aux battery ( follow instructions from Traxide ). Keep this wiring short - you can run this in the space in front of the radiator top tank in 19mm irrigation hose.
4. Fit connectors, fuses etc.
5.Wire all your devices ( fridge) etc to the new aux battery with fuse for each near the battery.

You're done ! forget it till you need to replace the battery in about 3-4 years.

I have a red top optima as a starter battery and a exide N50/70(i think can't remember but deffinatly an exide possibly marine) as the second...

I haven't moved my power steering reservoir as there was no need...

it is all hooked up to an Sc40 which sits comfortably on the inner mudguard opposite the main starting battery.

I bought the SC40 Kit from DriveSafe here which included all wiring etc to put on! All you need is the battery and then the wiring into the cabin. Best value for DB system imho.

Originally Posted by stooge

I bought the SC40 Kit from DriveSafe here which included all wiring etc to put on! All you need is the battery and then the wiring into the cabin. Best value for DB system imho.

x2 in fact it really is fit and forget...I have 2 sc40's on my car but I'm now taking one off to upgrade to a sc80 for the trailer.

Would I sell my sc40...NO because I think its such a great unit we are going to put it on the third car which already has a dual battery setup but I don't think its as good as drivesafes stuff so its coming out and the 40 is going in.

Originally Posted by TOTTHEAD

The system is electronically isolated, uses a DC-DC converter on the AUX line to provide the AUX battery a more dedicated form of recharging than simply relying on the alternator (explained below). Note that my system does not use 2 batteries to start, to overcome a flat or faulty start battery requires a jumper lead to be run from the positive of the aux battery to the start battery, this can be overcome by using another solenoid but the situation should not happen too many times for me at the moment to warrant that just yet.

Cut

DC-DC Converter: Electro Parts Australia Power Booster PB1120 20 AMP (Electro Parts Pty Ltd - Power Conversion, Automotive Electrical, Solar Power)

Cut

Because the Alternator is connected to the starting battery directly (in most cases), Once the starting battery gets back to full charge after recovering from the engine start, the alternator will drop the amps down and will only deliver a trickle charge. This trickle charge is also passed to the AUX battery, meaning that the AUX does not get the full brunt of the alternator only a trickle charge, as anything more would overcharge the start battery. To get around this I am using the DC-DC converter. The converter will take a small amount of voltage (2V I think) off of the starting battery (voltage which is compensated for by the alternator) and converts this voltage into a maximum (for this converter model) 20 Amp Output charge. This means that the AUX battery gets an exclusive potential 20 amps to recharge with, as the charge in the battery increases, the resistance will also increase and lowers the 20A charge down to a trickle charge.

Your whole setup is fine except for the DC-DC converter. The converters are more suitable to a situation where the charge voltage will be varying significantly (solar or wind supply for instance) or giving a nice constant supply of 13.8V to a device when the input is varying or fixed between 8-16V.

The regulator an automotive alternator regulates the voltage output of the alternator depending on the battery voltage. Current output is limited only by what the battery will accept at the output voltage of the alternator and the maximum current output of the alternator.

When the second (uncharged) battery is connected by the redarc/traxide type vsr to the fully charged primary battery the voltage that the regulator sees will drop (the batteries are effictivly paralleled) and the alternator will increase the voltage output to charge the second battery (anywhere up to 14.5 volts is typical). Your primary battery will also loose some of its charge to the second battery as they are connected.

By you placing the DC-DC converter between the redarc unit and the second battery you are limiting the voltage and current that the second battery can recieve plus you are loosing uncessary power in the conversion (no DC-DC converter is 10% effecient). Not to mention the fact that if you were converting an input voltage of 2V to 13.8V at 20 amps you would require an input current of 138amps!!! (assuming 100% effeciency of the converter).

Also I dont beleive a battery will fully charge if it is charged with only 13.8V. Drive safe will be able to add more about this.