Battery Charging Complexities

**drivesafe** · 15th August 2010, 07:02 PM

Hi fraser130, where have you got your AGM mounted?

**fraser130** · 15th August 2010, 07:46 PM

Drivesafe, the one I cooked was in my 130, under the rear seat, just above the muffler. we were driving home from a short stay near wangaratta, it was 38 degrees, and the batt was probably near to flat, when I stopped at a stop near seymour I couldn't touch the battery it was so hot!
I subsequently mounted a heat guard above the muffler, and that helped heaps, but now I have a Trayon camper, and the new battery is in that, so heat isn't so much a problem, but I am definately fitting a dc-dc inverter style charger soon.

Fraser

**pawl** · 15th August 2010, 07:47 PM

Originally Posted by drivesafe

A tip, if you find you need more power to be able to camp in one spot longer, simply add an additional auxiliary battery and you will take no longer to fully charge three batteries while drive than it takes to charge two. This is the biggest advantage of using an alternator as the primary charging source.

Hi drivesafe, if I did this would I just connect the two Aux. batteries in parallel then?

**drivesafe** · 15th August 2010, 08:02 PM

Hi Fraser, once you move the battery to the camper, you won’t need a DC-DC device, the cable length will protect the battery(s).

**drivesafe** · 15th August 2010, 08:04 PM

Originally Posted by pawl

Hi drivesafe, if I did this would I just connect the two Aux. batteries in parallel then?

Yes Pawl, and as long as your have 6B&S then you should have no problems charging the batteries while driving.

**fraser130** · 15th August 2010, 08:37 PM

Originally Posted by drivesafe

Hi Fraser, once you move the battery to the camper, you won’t need a DC-DC device, the cable length will protect the battery(s).

Possibly, but with it, I can't go wrong, and I can be sure I'm getting maximim charge, with current and voltage limiting.
I have 16mm2 DC welding cable all the way to the camper batt so over current could be a problem if the camper battery did end up too flat.
plus I know I'll get a full 3 stage charge profile even at an idle if I ever need it.

Cheers,
Fraser

**drivesafe** · 15th August 2010, 09:24 PM

Hi Fraser, before you waste your money on a DC-DC device, carryout some tests on your battery in the CT.

The reason I asked about the location of your battery is because I have never heard of a battery, AGM or otherwise, being over charged when it is fitted somewhere other than the engine bay, such as in the rear cargo area of a 4x4 or in a CT or caravan.

I have customers who have run 25mm2 cable to their caravan and never cooked a battery.

These DC-DC step ups are a bit of a con job.

Will they fully charge a battery, yes and will they do it quicker and better than an alternator, rarely.

If your battery only needs topping off than a DC-DC device will fully charge the battery quicker than an alternator can.

The problem with charging batteries while driving is that the lower the batteries are, when you start your drive, the longer you have to drive to fully charge the battery, no matter what type of charging you are using.

In most cases people NEVER drive long enough to fully charge their battery.

The biggest single drawback with having a DC-DC device is when you find you need more power than a single battery can supply so you add a second battery.

With your DC-DC device, you now need to drive about 90% longer to fully charge the batteries while just using your alternator, at very most you will only need about 20% more driving time.

For the very few occasions where these devices MIGHT do a better job than an alternator, the difference is so small that the cost of the devices is just not warranted.

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