Although I had planned to install a second battery in the rear of my disco to run my new Engel and whatever else strikes my fancy, it doesn't look like I'm going to get it done before the Steens trip.

Am I taking any chances of draining my main battery by leaving the Engel plugged in all the time? I'm told that they draw very little, but I havn't actually asked any one who uses one.

You WILL be fine as you'll drive the truck every day. Even if you left it on all day and didn't drive the truck, with a normal battery you'll be ok. I have a pair of jumper cables but you won't need to use them because of the fridge on this trip. Around day three on normal fridge setting is where you should turn over your truck. BTW here's some math I came up with. In this example I do NOT pretend to be an electrical expert and I'm taking a linear approach to voltage drop which I KNOW is wrong, but I'm simple:

- 70 amp hour battery topped off.
- Engel draws about 2 amps when on
- I estimate it would stay on for about 8 hours in 24 under 75F conditions with normal use. This is a loose estimate. A cooler bag for it does help lessen this number
- So in a day it'll draw off about 16 amp hours.
- It'll take you all of 11 minutes of running your truck with a 85amp alternator to put that day's use back into the battery.

Now that's real rough, but it's also my reason for not requiring a second battery. Just run your truck for a bit each day and you're gold. If you are worried, just get an inline amp and volt meter. I think there is one for the fridge some place that will actually shut off the feed to the fridge if the battery is too low. And it can warn you when the temp in the fridge is too high, covering both bases. but that might have just been in one of my dreams....with Morgan Fairchild, yeah......

Another point.  If you were to be in one spot for long, it'd be lighter to carry a small 20W or more solar panel.  I have one that weighs a pound.  On a really sunny day in the summer, you can expect about 8 truly useful hours of sun.  Most panels and systems are about 90% efficient in a DC->DC application.  Going on those assumptions,

20W in a 12V system = 1.6amps into the battery for 8 hours = 12.8amp hours back into the battery.   Even at 4 hours of full sun, you're doing well enough.

Get a nicer 62W model like this one and expect about 4 amps each hour of use, That whole 16 amp hour draw can be put back in with 4 hours of full sun. 

Or you can idle your engine for 10-20 minutes and be done.

I run my ARB fridge on the solitary spare battery with a solar panel to juice it up, needs sun though. Haven't been getting much of that lately.

In the desert with sun all day long I am very confident in the single battery keeping the fridge going very smoothly with the solar panel for backup. My spare is not hooked to the generator, only the solar panel. If you are  going to be running the vehicle you should be ok. Those of you with a double battery are sure to be ok.

I have got to figure a way to charge the spare when there is no sun.

Cheers,

Morris

I have ran my ARB fridge (same as the Engel) for four days at  my home without the rig being started.
When I did go to start it, it fired right up.

I do have a second battery though just in case, but have not had to use it yet.