Dual Battery - Charging

[Biggish]

I did quite a bit of research and I also like the concept of the DC-DC charger so I bought an "Echo" unit (15 amp IIRC) from HCDP Electronics. This is an intelligent charger and I have connected it to my 2 Deltec 105AH batteries which are mounted in the underfloor seat well at the rear of the Gen3 LWB.

I have installed heavy duty welding cable with 100A fuse and cole hersee switch from the main battery to the rear. This cable doesn't connect directly to the auxillary batteries but it provides power to the DC-DC charger (only when the cars ignition is on). Overkill to have welding cable powering the DC-DC charger - yes indeed! But electronics can and do fail when you least expect it. So should the DC-DC charger ever give up on me I can easily connect the welding cable to the batteries directly as an interim solution.

To date the system has worked flawlessly and I have never flattened the batteries completely even after 4 days of fridge & camping lights without charging.

Cheers
Bruce

[KaiV]

On the topic of Dual battery systems... My dual battery is gebuggered I doubt I'll replace it, how can I in the interim switch off the dual system? Do I just disconnect the thinner cables to the controll unit?

[Gemaskerde Tuinvurk]

Gathering from all the discussions over all the forums, DC-DC is the best way to charge a deep cycle.

So what size inverter do I need? I read somewhere that a 20amp charger will need a 450-600W inverter.

Has anyone done the DC-DC charger?

[LowRange]

This is a subject much like the old "what is the best oil?" discussion and I think that it would border on impossible to get a definitive answer so this is the route I went.

I started off doing a LOT of reading and research and I know a heck of a lot more about batteries than I used to. I have all the technical skill and experience to design my own custom circuit and build my own split charging system so I started costing and sourcing the needed bits and pieces. This is where reality kicked in and I found the savings made by doing it myself does not really justify the effort put in to the project. My system would have been based around the Cole Heresee solenoid and the cost of the materials came close to the nat luna split charging system. The deciding factor was the ultimate reliability of the system and the effect of finding out that I had overlooked a detail or two when the system fails somewhere in the bundu and all my steak defrosts.

So rather than reinventing the wheel I went with the nat luna and everything just worked out fine with the best part of the deal not coming in the package... Peace of mind
As soon as the alternator starts pumping power in to the starting battery a timer of 5min. is started and when it kicks in both batteries are connected to the alternator, when the vehicle is switched off the battery voltage stabilises at about 12.5 volt so when a voltage of 12.7 is reached the relay opens and only the second battery is drained. Simple and tested.

On the battery side I opted for a second crank battery as the time needed to fully charge a deep cycle was too long for me and I doubt that I will need to drop my voltage so low as to justify a deep cycle and with two 96 ah units I should be able to power a winch or weld without too much problem

One important point regardless of which system you go for is the wiring. Use the thickest cable you can get hold of (25mm - 35mm) and keep the runs as short as possible and solder all your joints to ensure good contact. Fit fuses to all your cable runs, 12v is a devil and folks tend to treat it with contempt, it wont shock you but it WILL start a fire quicker than you can blink your eyes.

I have been using the NL system as Henk described here for 8 years (in different vehicles) to charge TWO 105's installed in the Xplorer. We sometimes go without 220V power for up to 10 days and this system is more than sufficient.

[Gemaskerde Tuinvurk]

I have been using the NL system as Henk described here for 8 years (in different vehicles) to charge TWO 105's installed in the Xplorer. We sometimes go without 220V power for up to 10 days and this system is more than sufficient.

how frequently do you have to replace your batteries?

[LowRange]

I replaced the set in my previous Xplorer at just under 5 years. The one in the pajero is just over 4 years old and still fine.

At home I always make sure they are fully charged while not being used.

[Gemaskerde Tuinvurk]

Is it worth removing or just disconnecting the secondary battery when not using it?