Power use - 3 way fridge

Submitted: Sunday, Oct 19, 2014 at 18:03

ThreadID: 109863 Views:2480 Replies:3 FollowUps:2

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Peter56

I have a Chescold 40ltr 3 way fridge which draws 10amps when on 12 volt power. We use gas when stopped. Fridge has been great in all weather so the fridge is not my concern - I am embarking on a 5 week trip across the top end, and my concern is simply the ability of my 4x4 to keep the second battery charged. I have a 2010 Mazda BT50 with a properly wired second battery 100ah. If I travel about 400klm's per day, will the alternator keep the battery charged or will I be using more than the charge rate - the only other gear I will be using are mobiles and laptops with a few LED lights.
I suspect the battery will be depleted a little each day and within a week or 2 I will need to top up the second battery via 240v or solar - prefer not to cart solar gear.
Any thoughts please.

PJ

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Reply By: Slow one - Sunday, Oct 19, 2014 at 19:12

Reply By: Kazza055 - Sunday, Oct 19, 2014 at 19:58

Sunday, Oct 19, 2014 at 19:58

I run the van fridge directly from the alternator via the anderson plug. This is wire via a relay that operates only when the ignition is on.

Trying to run a three way fridge from a battery is asking for trouble.

AnswerID: 540563

Follow Up By: Member - sdr00y (Beecroft,NSW) - Sunday, Oct 19, 2014 at 21:59

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.