Dual Battery Systems

Hi Phil,

I can't agree with you in relation to the charging rate, regardless of whether the battery (or battery pack) is mounted in the engine bay or in the rear of the vehicle, the charging rate will be the same, provided of course the cabling is of sufficient size.

AGM and Calcium style batteries will charge quicker and more completely than a "normal" wet cell battery but the chances are that none will be 100% charged via the vehicle alternator. Now and again an external smart charger is best for complete charging of an auxiliary (deep cycle) battery regardless of where it is mounted.

Both the Blue Apple Thumper and the Sidewinder Flyer are good quality "battery packs" that come complete with all charging cables and isolators to provide a complete and flexible solution when mounting in the rear cargo area (or boot) of a vehicle. (The Flyer takes a range of battery types to suit your requirements)

Thanks Phil, Ken, Bill

I wish to use the set-up primarily for camping and longer trips so it sounds as if the 'second battery ' in a vehicle is better set-up for this rather than 'portable powerpack - thanksfor advice

Before you commit yourself, allow me to raise a couple of points you may like to consider.

In most vehicles the space in the engine bay will only allow a "standard" size battery and cradle.
When I first started out on a dual battery solution, I found the largest battery I could accomodate was an 80Ah wet cell battery. I found the wet cell to be lacking in the ability for efficient charging off the vehicle alternator.
I thendiscovered a significant restriction in that the fridge had to remain in, or close to the vehicle. Our camping style determined the flexibility for a portable battery system that could be removed from the vehicle along with the fridge and placed in the tent or camper annex.
For this reason we invested in a 75Ah AGM Thumper which we have found to be really useful. This battery system could be charged by the alternator when travelling, or via a solar panel array at camp. We used the engine bay mounted auxiliary when travelling to run the fridge and the Thumper when camping.

Then we changed our tug over to the Colorado diesel and no way could we fit a second battery in the engine bay. After some consideration the auxiliary battery solution was The Sidewinder Flyer mounted in the tub of the ute and containing a 100Ah AGM battery.
Again when travelling, the fridge ran off the Flyer and at camp we swapped over to the Thumper when removing the fridge from the vehicle. The flyer with a 100Ah AGM battery is not exactly "portable" although it is removable with effort, if required.

Lastly, it would be extremely difficult to mount an AGM battery in the engine bay, primarily due to the larger footprint of an AGM battery and also because AGM batteries don't like too much heat from the exhaust maifold, etc.

You may get away with an Optima battery, but when you weigh the cost of one of these, the last thing I would do is whack it in the engine bay.

Whichever way you go, you will need a heavy duty cable run from the primary battery, to an isolator, then to a suitable socket in the rear of your vehicle, where the fridge resides.

To me, the most flexible, cost effective and flexible solution is something like the Flyer or Thumper mounted in the rear to which the fridge is plugged into.

The Cost for a Flyer ($395) and a good AGM battery of reasonable size ($320 or thereabouts for a 100Ah) is around the $700 mark.

A "standard" dual battery installation of cradle,battery, isolator, cable and socket would be as much or more so why not give yourself the flexibility of a "portable" battery system?
Also, should you decide to change vehicles, you can swap the "portable" system over with just a minimal cost of a new cable kit.

The desision is yours and good luck with whatever solution you choose.