12v powerbank

Aston Martin

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I am not a doctor of electrical engineering.


I have a 12V Coolbox for my cab, but it's a stupid one so it has no thermostat or anything. I have to unplug it at night so it doesn't drain the lorry battery. I assume it's a heat sink and a PC fan? It works well tbf.

I'm thinking about using a powerbank to run it at night, during the warmer days. You can buy a 12V powerbank, but it's only 6000mah and it's ?35. :|

A quick googling...

http://www.ebay.co.uk/itm/New-DC-DC-4-5-32V-to-5V-55V-XL6009-Boost-Step-up-Module-Adjustable-LED-Voltmeter-/291981134359?hash=item43fb6e8a17:g:hogAAOSwo4pYXfI
+
http://www.ebay.co.uk/itm/12v-Car-Cigarette-lighter-kit-cig-socket-auxilary-aux-/281159131350?hash=item417663e0d6:g:qDYAAOSwcdBWT0PB

= :cool: ???



The Coolbox specs on website:

'Wattage is 40W
Draw in amps is approximately 3.5A from a 12V supply'


Is this doable? 40W seems to be high. The Coolbox says 40w underneath.
 

MXM

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You don't need the DC-DC converter if the powerbank and the coolbox are both 12V.

3.5A x 12V = 40W, so that makes sense. It will however drain the 6Ah powerbank in under 2 hours, so not really an overnight solution.
 

93Flareside

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12v powerbank

If you get a Honeywell wall thermostat it could cycle all night and not be on constantly. Those say they're for 24v but, they typically don't need the 24v for powering it, just passing between relays when the thermostat is calling for heat or cooling. The 24v comes from the furnace controls using it. They're powered by a battery.

Don't they make RV type thermostats?
 
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Aston Martin

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You don't need the DC-DC converter if the powerbank and the coolbox are both 12V.

3.5A x 12V = 40W, so that makes sense. It will however drain the 6Ah powerbank in under 2 hours, so not really an overnight solution.
I was going to use a normal EC technology powerbank 22400mAh. Which I would need the converter for as it's 5v.

But max output is 2.4amp
 

MXM

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I was going to use a normal EC technology powerbank 22400mAh. Which I would need the converter for as it's 5v.

But max output is 2.4amp
You can't directly compare capacities given in Ah if you operate at different voltage, gotta use Watt-hours. 5 V * 22.4 Ah = 112 Wh. So with a 40W load that's still under 3 hours, and minus 15% for boost conversion losses.

Also to supply 3.5A at 12V, you need to draw 3.5*12/5 = 8.4 A from a 5 V source. Practically 10 A, because again, the conversion losses. The converter is only rated for 4A input.
 

GRtak

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Why not just get a power adapter and plug it into the cord that would be used to warm the engine block? Otherwise, just get a small car or tractor battery.
 

Perc

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If you want to run a fridge off of 12 or 24V battery power for any length of time, it needs to be compressor based. Like your home fridge is, and your car A/C for that matter. The problem with these is size and cost IMO. The compressor takes up a lot of space and you're looking at several hundred pounds or more for a brand new one. Even more if you want a quality brand like Waeco or Dometic. These are designed to run 365 days a year and not flatten your battery if you leave it running in your truck over night.

All the cheap cool boxes are peltier based. They're cheaper to make and there's no bulky compressor inside, but they're far less energy efficient. The way peltier technology works means that they usually reach a tempreature of of 20C or so under ambient. This becomes a problem if you leave the truck parked in the sun. 40C in the cab, 20C in the cool box and spoiled food... or in winter, 5C in the cab and -15C in the box and frozen food. :p Compressor based boxes have a proper thermostat and can usually also reach freezing temps if you want.

I have a huge peltier based 12/230V box that cost a bit into three figures. It's better insulated than the crappiest ones and peltier is OK for my use case because the only time I use it is on road trips. When I reach my destination I take it out of the car and plug it in to 230V. I would never have one if I lived in a truck all day. I would cough up the money for a proper compressor box for sure.

edit: https://www.dometic.com/en-gb/uk/products/food-and-beverage/cool-boxes/powered-boxes/dometic-coolfreeze-cfx-28-_-64076

edit again: https://www.dometic.com/en-gb/uk/products/food-and-beverage/cool-boxes/powered-boxes/dometic-coolfreeze-cf-11-_-82058
 
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Aston Martin

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Thursday morning i put a 2l bottle of ice and a 750ml bottle of ice in at 6am, coolbox was on until 8pm and unplugged for about an hour in between. Turned back on at 7am and there was still ice at 4pm Friday.

Not the best solution, but it works i guess.
 
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