Aux battery

Hi Rob,

Firstly. let me state that I am not an Auto Elec. or a 12 volt expert, just someone who has been camping on and off road for over 50 years.

A dual purpose battery is a compromise battery, it will not deliver all the benefits of either a cranking battery, or a deep cycle battery. IMHO, you would be better with a dedicated cranking battery for what the vehicle needs, and a seperate deep cycle battery for ancillary items such as fridges etc. There are plenty of people who like you have used a dual purpose battery quite successfully.

The next issue you raised is where to put the auxiliary battery. It is better off inside the cabin, but you can put them under the bonnet if you can protect them from any heat sources, not always easy.

If you intend keeping the 80 series for some time to come, have you considered a LiFePo4 battery and appropriate DC/DC charger for an auxiliary battery? If you can afford it, this would be the way to go.

Macca.

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Hi Rob,

The "Century Marine Pro" is a "good" battery. How long did your present one last?

It reads as though the Pirahna DBE180SX, is a high capacity VSR and ONLY accepts 8 amps of REGULATED solar, ie, no internal regulator of it's own. Looked at the Fish site to see. That is small input of solar to a fridge battery and may not keep up while stopped. Therefore, depending on the previous success of the Century, as Alan asked about, and the desire to use an AGM, the battery is still affected by the alt max voltage, AGM's like around 14.4 v up to 14.7 to attain full charge and the alternator may not be ever charging it fully so always behind the 8 ball. If alt reg is down in max reg voltage you are pushing for any battery use ebven though it supplies the star battery reasonably well.
You can use an AGM under bonnet, some claim that ability to sell them. However, serious insulation of reflective foam board under and at sides would heat insulate the AGM battery fairly well. Most people never do that at all. If near front of engine bay, and with sufficient radiated heat insulation, the battery can be duct fed cool air nearly all the time while trying to be heated by engine. Duct cooling to specific engine bay areas does work. I have used it preciously also on petrol engine ignition modules which fail from heat. After a couple of failures of distributor modules the added ducting and subsequent cooling cured the problem. Batteries love it too.
If duct supplies air to the air gap between battery and insulation panels it remains and operates cooler. Owners can do many things to improve component reliability if the issue is seriously considered.

Hi Rob
In my 2008 V8 Diesel 70 series Troopy, my previous two Century Marine Pros lasted 5 years.

I now have two Century Dual Force AGMs with a 2 year warranty. They are made for 4WD under bonnet use. I emailed Century about their recommend voltage for my vehicle and they recommended 13.8 to 14Volts. I then installed a HKB Adjustable Voltage Booster to set this voltage.

AGMs charge at a quicker rate than flooded batteries, but how long will they last – only time will tell.

Hi Rob - I have high battery usage with 2 Fridges in my 4WD and AGM is a better option for me over flooded cells.

The leading advantages of AGM are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded is specified at 50 percent DoD to attain the same cycle life.

That’s the reason I use AGM over flooded batteries. They can be close to 100% charged in two/three hours by a conventional vehicle alternator/regulator. Normal vehicle charging systems take flooded batteries up to about 70% charge, often less. If Discharging to 40 or 50% - this limits effective usage to 20 or 30%.

AGM batteries can be quickly charged to well over 90%. They can also be safely discharged to 40% or so without damage, and to 30% without seriously shortening their life.
This gives me an effective usage of 50 to 60% - about twice that of similar-sized flooded batteries.