Chest Freezer / Inver Configuration

[Hmanfl]

Hello to All
I would like to ask the form's opinion on the attached Chest Freezer conversion and
ask if someone could provide me with the formula for finding out many dc amps
a freezer will draw from a battery bank if the AC amps and run times are known.

Thank You for your Help !

[Cariboocoot]

Looks like the thermostat triggers both the freezer compressor and inverter when needed, thus keeping the inverter off and not drawing power when it isn't needed. Should work, although some inverters' on/off controls do not remove all their power draw. It may be simpler to use one that has a standby mode and let it pulse, especially as not all inverters will like being turned on with a load present on the AC (the ones designed for standby do not suffer from this; they are designed to do it).

As for the power draw it's pretty much a matter of AC power factored by inverter efficiency plus inverter draw. So if the freezer uses 120 Watts @ 120 Volts (10 Amps) and the inverter is 90% efficient that's 134 Watts @ inverter Voltage (11.6 Amps @ 12 Volts) plus inverter draw (20 Watts perhaps - another 1.6 Amps) = 13.2 Amps.

But (and it's a big one) there will be extra power consumed on start-up, additional power loss in the wiring, and the ever-present Peukart Effect on the battery which makes the current draw non-linear as the battery Voltage changes (and alters the actual capacity as power is drawn). You can come close to predicting it by rounding the consumption numbers up, as in 12 + 2 = 14 Amps at nominal 12 Volts. 33% duty cycle over 24 hours would be 112 Amp hours per day, necessitating a minimum 224 Amp hour battery bank. Or, curiously enough, a couple of standard golf cart batteries in series.

Not that I've ever done that calculation before or anything.

[Hmanfl]

Thank you for your help !

I am looking on Craigslist for used freezers, small chest types and most of them are rated 1.3 to 2.0 amps.
I know the start up amps will be higher, but using the Johnson control to operate the freezer as fridge will
reduce the run time cycle.

So if the freezer / fridge is rated at 2 amps @ 120v = 240 watts , how many dc amps will it be pulling per hour for one hour of run time ??
Omit the inverter overhead and Peukart Effect for now.

I am trying to see if my current batteries can support this load and how long a run time they can handle.

Thank You

[Cariboocoot]

Thank you for your help !

I am looking on Craigslist for used freezers, small chest types and most of them are rated 1.3 to 2.0 amps.
I know the start up amps will be higher, but using the Johnson control to operate the freezer as fridge will
reduce the run time cycle.

So if the freezer / fridge is rated at 2 amps @ 120v = 240 watts , how many dc amps will it be pulling per hour for one hour of run time ??
Omit the inverter overhead and Peukart Effect for now.

I am trying to see if my current batteries can support this load and how long a run time they can handle.

Thank You

Omitting the fine details? It's simply a matter of dividing the Watts by the Volts to get the Amps. So 240 Watts / 120 Volts is 2 Amps, and the same 240 Watts / 12 Volts is 20 Amps. 20 Amps used for an hour is 20 Amp hours.

But when you do put in the inverter conversion efficiency it gets worse: 240 Watts on the AC side is suddenly 266 for the batteries to supply.

By the way, that isn't a very good power rating for that freezer. My 16 cu. ft. Frigidaire does better than that without any conversion. In fact it uses about 1/2 the power. I would not trust the numbers on the freezer's tag, but rather plug it in to a Kill-A-Watt and see what it really uses. I know; impossible to do until after you've bought it and then it's too late.

I hope you take some time to read through the thread on "How bad a small refrigerator is" in this section; there's a lot of real-world testing data in there you might find helpful.

[waynefromnscanada]

Thank you for your help !

I am looking on Craigslist for used freezers,

Used freezers are usually at least a few years old, and much harder on energy consumption than new, high efficiency Energy star basic models. You could do well to go for a newer high efficiency model, would pay off in the end.

[Hmanfl]

I have read waynefromnscanada's very helpful post on his results. His result are what got me working in this direction. Hats off to you Wayne !!.

I should tell you that this setup is not for home use, but for camping.
We live in Florida and the family likes to camp allot. We have 80 qt marine coolers to keep ice and food in.
I wanted to find something that worked better and lasted longer than the coolers. I have good supply of used batteries from the local recycling place.
They sell them for about $1 each, I have found some very good ones from time to time.
Over time I have built up a battery bank of about 400 amp hours. I use them for the kids games, led lights, phones and one time to run 2 electric
blankets over night during a cold snap, so I have a good bit of extra capacity. I also have one solar panel of low output to recharge them when needed.

So I am hoping to try a chest freezer conversion to fridge and give that a try. I would load and freeze the contents the day before our trip. Then run the
freezer as a fridge to slow down the melting of the ice and food items. If it works for 2 to 3 days before I run out of power it will be a win. I can buy less
ice and make it last longer. Most trips are 3 day. We have a cargo trailer with all the gear in it. It stays loaded except for food.

I know it would take a lot of trips and savings on ice to pay for this setup, however it would also give me another food storage
option during a bad weather event.