Sunday, Oct 19, 2014 at 21:59
Peter and Kazza055,
Running the fridge the way Peter has it, via a second battery is fine. While running the vehicle the vehicle alternator will provide more than enough power to keep the fridge running and the battery full. The added bonus of running a battery is if you stop for lunch the fridge stays running rather than stopping while the car is not running.
3 way fridges don't run particularly well on 12 volt anyway but if you use gas or 240 volt overnight and only use 12 volt during the time you are driving your battery will cope. That's the way I run mine and I have never had an issue.
Having said that, mine is a 1995 troopie with an old school alternator, ie it charges all the time. Some new alternators, on prados but not sure about your car, do sense the main car battery charge and 'turn off' the charge when it is full. That's why some new cars need to have dc to dc chargers rather than the old dual battery solenoid type chargers.
Peter, check with your user manual or your local dealer to find out if your alternator is the type that switches off. If not, your second battery (as long as the wiring is nice and thick) will stay charged while the vehicle is running your 400 km a day.
One cheap and easy thing to do to give you piece of mind is fit a battery monitor. I have found the cheapest and very reliable type is one for about $15 at Jaycar. The cat number is QP2258 and it's called a 'battery, charger and alternator tester'. They have clips that clip onto the terminals of the battery and 6 led lights that show how charged a battery is. I just disconnected the clips and ran the wires to my batteries (I have 1 unit for each battery and you'll need a bit of extra length of wire) and leave them on all the time. When you are driving you can glance over and see usually 5 led lights illuminated to show the battery is sweet. And at about $30 for two its the cheapest dual battery monitor I know. They do sell 24 volt ones that look exactly the same so make sure you get a 12 volt one or two.
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