bindi&us said:
I found one of these used for $80....
http://www.my12voltstore.com/P_95_Travel_Saver_p/p95.htm
Draws 4A. Wonder if I should get it till I can afford better for our upcoming van build (if the van deal materializes)??
It has no AC adapter and online they seen to be about $40.
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Do not waste your time or money with a thermoelectric cooler.
They draw 4 amps at 100% duty cycle. 4 amps always, and they can only do 35f below ambient, so warm ambients mean unsafe food temps.
With danfoss bd35 compressors, the compressor speed is variable, from 2.2 amps to 6.5 amps. 2000 rpm to 3500 rpm, and anywhere in between.
The manufacturer decides which speed to run it at. The higher the compressor speed, the faster the cool down, the higher the amp draw, and the lesser the duty cycle. But the lowest compressor speed which maintains sub 39f and stays under a 50% duty cycle is most efficient.
My Vitrifrigo was set for 2500rpm. I removed the resistor to drop it to 2000 rpm.
Some chest style fridges automatically adjust the compressor speed, and one can decide to wire in a potentiometer to adjust the speed manually on other Danfosses. It is just a resistor inline on the thermostat circuit. I just removed mine for 2000 rpm.
The Fridge cabinet should be sized to allow extra insulation and slightly different dimension fridges. Make it wider to accommodate more insulation, make it rest on a moveable shelf so one can later adjust the height. I had to do some minor modification when I replaced the Norcold with the Vitrifrigo. Most important is letting the condenser breathe properly. This cannot be stressed enough if the goal is efficiency. A couple passive holes to let the heat out is not gonna cut it.
It needs to be able to draw in cool air from below. The Danfoss controller can handle powering .5 amps worth of fans. the fans that generally come with the fridge are 1/5th of that. I upgraded the fan to a quieter one which draws 0.05 amps, put it on the other side of the condenser and made a low tunnel so all the fans flow is concentrated through condenser, and it cannot recycle any preheated air. I've no need for an additional fan but having that option is one I like and can make one's install much easier.
Don;t just get any computer muffin fan. the technology on these fans can be impressive, or laughable.
Here is impressive:
http://www.noctua.at/pdf/infosheets/noctua_nf_f12_focused_flow_web.pdf
The quality of your install, the insulation and the ventilation will be a huge factor in overall battery consumption. Plan for some adjustability and look at dimensions of modern fridges you can replace that older model with and plan to be able to slide a modern fridge in with a few modifications, or perhaps none, if you plan far enough ahead.
The old Norcolds developed bad reputations (Never cold) because of improper installs where the condenser heat could not be dissipated properly. More recent designs force a minimum of ventilation into the design.
Another area is to keep the interior ambients as cool as possible, with exhaust fans, and reflectix in the windows that face the sun.
Also insulate the van body adjacent to the back of the fridge. I left an airspace here, but many layers of reflectix and a white body means no heat gets through to make the fridge work harder, or heats up the air lowing into the condenser.
