Battery life while running a fridge.

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Hello!  Looking to purchase the Nexus Power Station 3000w (2000w continuous).   I'm trying to do the math on a simple idea:  assuming a fully charged unit with 4 batteries, how long will this run a standard household fridge before the batteries completely discharge?
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Scotty

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Posted 3 months ago

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summetj

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This 21 Cu Ft fridge:
https://www.sears.com/kenmore-61212-21-cu-ft-top-freezer-refrigerator/p-04661212000P?gclsrc=aw.ds&am...

uses 472 kWh per year (average estimate), so approximately  1.31 kWh per day to operate.

A brand new 7.5 AH battery has 420 watt hours of capacity (0.420 kWh) so with 4 batteries you'd get 4x 0.420 = 1.68 kWh of capacity. You'll probably only get 80% efficiency, so 1.34 kWh of power to the fridge...or just about 1 day (24 hours) of run-time.

However, in a power outage situation, you could probably keep food "cold enough" for 2-3 days by following the following procedure:
1. After the power initially goes out, keep the fridge closed all the time. Don't bother plugging in the fridge for the first 12 hours, let it ride for a while on it's stored thermal mass.
2. About 12 hours in, plug the fridge into the power station, and run it continuously until the fridge compressor turns off (you'll see the watt draw go down to an idle load when this happens). This means that the fridge has reached it's "cold" operating temperature.
Turn off the power station to save battery power, leave fridge closed as much as possible to keep the cold inside.

2a. Repeat every 12 hours until your batteries die.

(Edited)
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Scotty

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Thanks!  This is great stuff -- much appreciated.  My math was a bit different, but I also wasn't sure of the specific max battery capacity.  I appreciate the confirmation.  This is a great benchmark to determine what I can and cannot power should there be a power outage.  I have a gas generator I can use to charge the EGO system (this keeps the generator from running 24/7); or use the generator for temporary heavy draws (heat; AC; washer/dryer).  Thanks from Scotty in sunny New Mexico
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summetj

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Batteries are a good complement to running a generator intermittently, but if you plan on doing that, I suggest you buy 4x of the rapid chargers. This will allow you to charge 4 of the 7.5 (or 10?) AH batteries at once in just under an hour.

The ego power station itself is about as good as a single regular/slow charger, and it would take hours and hours to recharge all four large batteries using it in "re-charge mode". (It charges at a rate of 170 watts or slower when plugged in...which would take 10 hours to recharge four 7.5 AH batteries...)