I am trying to run a fridge from the mains instead of battery. My biggest problem is that I need to somehow get the power from 230VAC to 12VDC 100amp!

Any suggestions as to how I could do this would be appreciated!

 

Welcome to AAC!

Firstly, state the make and model of the fridge.
Secondly, state the power requirements of the fridge. This should be in the User Manual or on a plate at the back of the fridge.

Presumably, the fridge was designed to be powered from a 12V lead-acid battery.
Next step would be to locate a 12V battery charger of the right amperage. If the output voltage is too high there may be ways to lower the voltage,

 

Thank you!

Power requirements for the fridge are 12VDC 100amp.

It is currently just being run on a heavy duty battery.

 

That's 1.2kW.
I suggest you check again. A typical fridge only takes about 60W average or 1.4kWh/day.

 

Maybe it is 100Watts?
100Amps sounds like a heater, not a fridge

 

I suspect TS is reading 1.2kWh consumption per day.
I think 12VDC @ 5A = 60W would be closer to what is needed.
(Nominally 12VDC input, could be as high as 13.8VDC)

 

You can get a PS like this off of ebay (assuming it's 12V 5A and not 12V 100A). But please, do not do the mains wiring yourself if you are not very familiar with mains. If you want to avoid any mains wiring altogether, you can get one like this (cut the 12V wires and attach the proper connector). While 10A or 17A is overkill, it means you will not have any issues in the long run.

 

I have a 19 cubic foot Whirlpool sitting here with a top freezer. Refrigerator Volume = 14.08 cubic feet and the freezer is about 5 cubic feet.

Total power consumption when it is making cold, compressor running is 6.5 AAC @ 120 VAC = 744 Watts and while not a gadget loaded monster it is a plenty large unit. With only my wife and I in and out the compressor doesn't run much. The end result is how much power to make this much cold in a box this big. So if I want the same cold using 744 Watts at 12 VDC I am looking at about 62 Amps when the compressor is running but that is only for short periods of time.

Ron

 

If it is 100A, then get a few of these and combine all the 12V outputs in parallel. Don’t get a 12V 100A power supply, as they will be 2-3 times as expensive.
https://m.ebay.com/itm/Cougar-Power...AOSwva1a8y5Z:sc:FedExHomeDelivery!10504!US!-1

 

That's 1.2kW.
I suggest you check again. A typical fridge only takes about 60W average or 1.4kWh/day.

But the power supply has to supply the peak demand, not just the average.

While average is useful for estimating battery life, the peak current (power) draw is what is required in this case. If the compressor has a 5% duty cycle, then that 60 W average turns into 1.2kW peak and the 12 V supply would need to be capable of delivering 100 A.

But I think 5% is unrealistic. My understanding is that duty cycles are typically between a low of around 30% to a high somewhere around 90% with 40% to 60% covering most.

@rob9865: Please provide the make and model of the fridge.

 

Maybe a simple transformer, rectifier, and capacitor are best suited here. It might be possible to get cheaper components that can handle the peak power demands but not supply them continuously.

 

Oops!
I forgot about the duty-cycle thingy.
Ok, let's go with a worst case of 20%.
Then we need 12VDC @ 25A PSU, something like this:

https://www.amazon.com/dp/B06VWV5YCH/ref=psdc_1161760_t2_B00D7CWSCG

 

It is most likely 100A/h or 100A peak supply from the battery. A battery fridge is less.

 

Hi everyone, thank you for your help!!

On the plating on the fridge it says:

Max Power absorption: 100Amp

Does this then mean like suggested in the thread that I don’t need the 100amp as it’s only the max power...

 

Please give a picture.

 

Photo is of the serial plate

 

I wonder if that 100Amps is the starting surge current. It does say maximum.

 

It is most likely 100A/h or 100A peak supply from the battery. A battery fridge is less.

And what, pray tell, is 100 A/h? So after six minutes it's 10 A and after 10 hr it's 1000 A?

Aside from being proportional to the voltage across an inductor, that unit has little meaning and none in this case.

 

I wonder if that 100Amps is the starting surge current. It does say maximum.

That would be my guess. It might be possible to supply that peak with a capacitor, but we would need to have a good estimate of how long the surge lasts. Now that we have the nameplate info, perhaps someone can find some additional info -- I don't have the time right now.

 

Hello,

The 1600 Watt version of the powersupply on this ebay page will be capable of 100 Amps:
https://www.ebay.com/itm/NEW-750W-2...ca:m:myDSmjietw9WI3FnbhsIeTw&var=552769209065

Bertus