Refrigerator UPS using a Growatt 3000TL LVM

Desert_AIP

Solar Enthusiast
Joined
Apr 5, 2020
Messages
60
I have an all electric house.
Several years ago I built a UPS for my refrigerator with a Cotek 24V inverter and charger. I used several relays directing the output so it would maintain the batteries when on grid power then auto failover to the inverter when there was a power outage. It provided about 24 hours of backup, and had an input for a generator to refresh the batteries.
The goal was to keep the refrigerator running if there was an outage while we were away, and to be able to run the refrigerator at night during an extended power outage so we didn't have to keep the backup generator running all night.

I spliced a twist lock outlet and corded plug inline the refrigerator circuit.
The circuit travels from the breaker to an outlet, then the corded side connects to the wiring running to the refrigerator.
I can either plug in to the outlet, running straight off the grid, or place the UPS in between the outlet and plug and have utility power and battery backup.
I'm using twistlocks specifically so they can't be knocked loose.

It worked, but took up a lot of space, and the charger wasn't matched well to the new LiFePo4 battery I built.
The box I built was 24x24x24 on 8" casters and took up a LOT of space in the garage.

I recently replaced the contraption with a Growatt 3000. I reused the LiFePo4 battery.
The new install is a lot cleaner, takes up less room, has higher utility charging capacity, is programmable for lithium batteries, and has PV charging option. So in an emergency I can set up the panels I have and keep the fridge running indefinitely.
I was able to install it in an out of the way corner in my garage.
I also included a derived load center with separate input and output circuit protection, and have a second outlet for a small fridge in the garage.

Old version
Ref_UPS_Cart_Front.jpg

Ref_UPS_Electronics_1.jpg

New version
Refer_UPS_2_54.JPG

Refer_UPS_2_53.JPG
 

Desert_AIP

Solar Enthusiast
Joined
Apr 5, 2020
Messages
60
I got ~32 hours until exhaustion in my test. I have a 24V 190Ah LiFePo4 battery now.
Once the inverter kicks on to supply the load, the efficiency increases.
I haven't seen much problem, but haven't metered it. It's doing what I want it to.

I need to do a long term, like over the weekend, test with solar only.
I have two 150W panels I hook up in series to feed it.
I need a couple larger panels to get by in Winter.
The fridge consumes around 2.4kWH per day.

Playing with this thing makes me want to permanently mount an array and run full time on solar with utility as backup.
 

sunshine_eggo

Happy Breffast!
Joined
Oct 26, 2021
Messages
905
Location
USA
4.56kWh battery
Fridge - average 100Wh/hr
3.2kWh fridge use
1.36kWh idle burn/inefficiency.

So, idle burn/inefficiency consumed 1.36/4.56 = 30% of your battery capacity.

300W of panels will be insufficient to provide indefinite backup power as that will only get you 1.5kWh/day with good sun. Likely need 900W of solar if you plan to use it for indefinite fridge backup.
 

Desert_AIP

Solar Enthusiast
Joined
Apr 5, 2020
Messages
60
That's what I think I calculated. 1KW min, which is what started me thinking of a permanent array.

I've built a couple smaller systems for camping.
I have a 54Qt 12VDC fridge and a 280AH 12V lithium battery. I run one of those 150W panels indefinitely. The fridge will run 5 days on the battery alone.
 
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