Simple battery advice

Gday Brad

I put some simple figures in post 36734 with voltage readings using an 80l waeco and 2x 80 amphour exide extremes. There are better (and more expensive) batteries around, but the local exide dealer looks after me and we both think the extremes are good value for money.

I have got 48 hours out of 1 battery, but I had a few frozen thngs in the fridge defrosting which would help. Personally, I don't need a decent charger, as the 3 batteries charge from the car, and I rarely stop for more than 2 nights in the same place. If I was to stay longer, I would consider a better charger ( and gennie), but at this stage I'm happy with what I have.

It would also be worth considering a good 3 stage charger for battery maintinance while parked up for a period of no use. I don't have to deal with this as 1 aux battery is always hooked up in the car, and the other is in a portable box and is used in the car and boat, so gets regular use.

I hope this is of some help, battery setups are a little like tyres, very subjective, and each to their own in most cases

Cheers Andrew

Hi Brad

Sounds like all you need is a better/bigger battery in the CT.
How long does the existing one last ?

Even with no markings a battery supplier should be able to tell you by looking, what size it is, so to advise you on a larger one.

Sounds like you need > 100AH.

Make sure you get a deep cycle type.

The idea of charging from the car works well enough, when doing reasonable amount of driving with your heavy duty wiring.
If start engine up after a couple of days to re-charge battery keep the revs up to
1500 or so to make charging faster.
I modified my Patrol so that it could be set to idle fast, saves holding foot on pedal.
A simple hand throttle or something may be possible for your car.

Important that your fridge low voltage cut is operative, to save fully flattening batteries.

If the opportunity to charge is going to be available then get a Jaycar MB 36-12 charger.
At about $95 its a simple, connect and forget auto-charger that weighs little.
And take an extension cord so that you can plug charger into the odd convenient outlet.

Robin Miller

It's worth considering an AGM battery. Heaps of info available on them on this forum if you do a search. Also check out this link for some good info:
www.fridge-and-solar.net/batteries.htm

AGMs are maintenance free, can accept a high charge current to charge quickly and don't discharge (or do so very slowly) when not used, so don't need to kept on trickle charge. Very handy on a CT.

They are a bit more expensive, but well worth the investment in my opinion.

I've been running two Fullriver 120AH deep cycles for over 12 months and they have been excellent.

Brad. To last 3 days away from a power source you will need a minimum of 130 amp hour to run your Weako. (idealy 150 to 180AH) Something like a Trojan deep cycle 30XHS would be sufficient. Unfortunately the quality batteries that can deliver that power will be over the $200 mark but should last 6+ years making them value for money. AGM's are great but may need 2 to get the required capacity.
With a 130 AH batt you may be required to run your engine for 30 minutes a couple of times if the weather was hot or you regually opened the fridge & replaced drinks. An alternative would be to have a smaller battery & carry a generator or solar panel.(No not my 1st choice either)
Cheers Craig..............

I didn't notice the 3 day issue before. Don't want to start an argument, but I seriously doubt that you will run an 80 Litre fridge for 3 days on one DC battery unless the ambient day time temp is below 24 degrees and overnight is real cold. even at that, you would want to be in the shade.

Under normal conditions, this fridge would have to draw 60 to 70 AH per day (but I have no personal experience with it). Only 50 to 60% of a deep cycle batteries stated capacity is usable. Do the maths and you need about 300 AH. Any less and you will dramatically shorten the life of the battery by deeply discharging it. Or you need to get some charge into the batteries along the way.

From my experience, ambient temp has an enormous impact on power consumption of a fridge.

Thank you all for all the easy to understand advise in such a short time..
So its 3 stages and 130ah.....
If you see me drinking warm home brew in Karijini you'll know I still managed to stuff up. :)))

Waeco UK have tested the FF90 in 30 degree temperature and found that it averages a 45% duty cycle and therefore uses 59 amphours per day.

In the real world with frequent opening, sun heating the fridge etc you may find it uses 80 amphours per day.

So for 3 days you will need to have 240 amphours.

AGMs can be discharged to 20% remaining without disproportionately reducing their life, so you will need 300 amphours of battery capacity just for the fridge.