We had a power outage here last Friday that lasted about 19 hours. (It
was caused by a wind storm blowing a large tree into power lines a few
blocks away). I happen to have four 100 Ah LiFePO4 12v batteries near
my circuit breaker box. (Their normal use is to power my boat during
the summer, but they were just being stored in the basement this time
of year). I also have a 1500 watt 12v to 120 VAC inverter. You can
probably see where this is going... Can I power my
refridgerator/freezer during the power outage using the inverter and
one of the 12v batteries? I thought, why not give it a try?

The refridgerator/freezer is a Sub-Zero brand built-in side-by-side
that is about 15 years old. If you aren't familiar with these, they
have separate systems for the refridgerator and freezer (ie, two
separate compressors). It has a dedicated 15 amp circuit, so it was
easy to pull the breaker and separate the wires from the breaker box.
I did that and then put a regular three prong plug on the end of the
wires and plugged the plug into the inverter socket and gave it a try.
The Sub-zero powered up normally and appeared to run. It drew about
800 watts for short periods and about 100 watts for longer periods.
(For example, 800 watts for 20 seconds followed by 100 watts for 2
minutes ... then repeat). So far, so good. After an hour or so, the
refridgerator section was back down to its normal 38 degrees F, but
the freezer temperature was slowly rising rather than dropping as
expected. Near the time the power was restored, the refridgerator
temp was still at 38F, but the freezer had risen from 0F to 22F. In
other words, the freezer wasn't really working at all. When the power
came back on, I restored the circuit to normal. Within a short time,
the freezer was back down to 0 and everything was back to normal.

So, my mystery is why did the refridgerator run normally off my
inverter but the freezer did not? The inverter is of the sine-wave
variety. I don't have a scope to look at the wave form, but it kept
the voltage up at 114 VAC even under the heaviest load (measured with
a Fluke 87). It was 120 VAC with no load. I would like to understand
this so I can use this setup during any future outages.

Thanks,
Pat