Small battery backup

ktyv

New Member
I'm looking to dip my toe in the water with, what I think is, a relatively small project. We have decent rates for grid electricity now, but the reliability is not great. Our main concern during an outage is the contents of our refrigerator and chest freezer. Using a killawatt, the refrigerator averaged 80watts/hour over 42 hours with about 85watts while the compressor was running. But, its rated for 445w during defrost and 120w for icemaker (maybe they can be temporarily disabled?). The freezer is averaged 20 watts/hour over 22 hours and 65 watts while compressor was running. It has no defrost. We have a standby generator that we use, but I'd prefer to avoid pulling it out for a short outage or running it overnight. What I'm considering is a battery with inverter and charger, that would be capable of running these two appliances for 6-10 hours and could be relatively quickly recharged (generator or grid). What I'm finding information on seems too small or too big (or expensive). Anyone have any comments/suggestions?
Thanks
Keith
 

12VoltInstalls

Solar Addict
What is expensive? Not a ‘smart’ comment but looking for your budget expectations

200W solar panel kit with a PWM controller and cables is US$240. Solar ATS $140ish, 200Ah of useable FLA battery bank as little as ~$300?-ish, lower cost inverter another $300

I didn’t do the math but off the hat that is just barely enough battery; the solar extends the up-time by daytime contribution.

Now that that’s out of the way: you can simply unplug the icemaker inside the freezer compartment.

The defrost cycle, however, is more complicated. There’s videos out there of how people have overcome that obstacle but that’s done by an electronic timer- I’m not convinced this is easily defeated especially due to the number of people who seek out new fridges without a defrost cycle…
 

ktyv

New Member
The last outage we had was about the worse case scenario. The power went out a couple hours before the kids bedtime. Let's wait and see if it comes back on quickly, but by the time we realize its not going to come back quickly, its too late to pull out and start the generator. And the power comes back on sometime in the early morning hours, so the food cools back down before I can see how warm it feels. Potentially 10-12 hours with no power, and no idea how warm the food got. Even if the battery lasts half the night, I feel good that the fridge can maintain temp well enough for the second half of the night. 8-12 hours just seems too long.

Solar panels aren't a factor as if the suns out, I have no issue running my gas powered generator. I'm just not comfortable leaving the generator running at 2am. Very noisy and I don't like the idea of leaving it unsupervised.

With the chest freezer only drawing about 22 watts per hour, it feels like I could just about stick it on a consumer level computer UPS and be done with it. But I'm seeing those have re-charge times of ~24 hours, which would be fine if the outage is limited to a single night. I'm also more confident in the chest freezers ability to maintain temp without power. I'm more concerned about the fridge. Sticking a couple 2L frozen bottles in there would help, but I still won't know if the temps good.

As far as "expensive", this is partially an experiment and partially a solution to a situation that doesn't happen too often. When it does, it probably means several hundred dollars of spoiled food. A thousand dollars for a prebuilt jackery type thing feels "expensive" to me.
 

circus

Solar Enthusiast
I'm more concerned about the fridge. Sticking a couple 2L frozen bottles in there would help, but I still won't know if the temps good.
Guess you'll just have to invest in one of those $15 indoor outdoor wireless thermometers, unplug the fridge and find out.
Wonder if the metal box would act as a Faraday cage?
 

Short_Shot

Photon Sorcerer
Several frozen 2 liter bottles of water should tide you over one night. Battery of sorts:rolleyes:
Do you get a forecast for power outages that let you do so, or do you just waste space with bottles of water?

At any rate 6 to 10 hours isn't an issue with a full freezer but tends to become a problem if it's empty. "Several" 2 liter bottles just takes up space and doesn't prevent things from thawing out any better than a full freezer does.

Even so, some portions will still thaw.
 

12VoltInstalls

Solar Addict
thousand dollars for a prebuilt jackery type thing feels "expensive" to me.
Ok - so $1000 isn’t expensive? Just the jackeryhackery is expensive? I’d agree with that.

Your 100Ah lithium, a true sine inverter, and an appropriate 120V lithium charger/maintainer will cost about the same (or $100 less probs) as the basic panels’n’batteries , ATS setup i mentioned ^above. For a longer up/run time and the opportunity to power other items if you wish.

Lithium Iron 100Ah is ‘roughly’ about the same output as two Group 27 Deep Cycle Lead Acid batteries, probably a bit more. The ~$300 battery price above is about the cost of four Group 27 FLA fyi

It is ok to use your generator as you wish, but dollars>=<dollars you may not have to deal with the generator at all- though it’s good to have for sure.

You have the wild hat guesstimate costs of the options. You’ll need to decide the best route for you but let us know what you decide and why. I- at the very least- would be interested to know.
 

circus

Solar Enthusiast
You’ll need to decide the best route for you but let us know what you decide and why. I- at the very least- would be interested to know.
I'd also like to know , if you do it, how long and how cold ice keeps a fridge. Modern fridges and old ice boxes have fans so maybe include a battery powered fan.
 
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Q-Dog

¯\_(ツ)_/¯
Real world experience. 2.5kWh should be enough battery to keep both boxes cold through the night. The battery might be completely flat when you wake up but after 10 hours the cold boxes should still be cold. I ran tests and my 10 year old refrigerator/freezer is fine for 2 hours without power as long as the doors stay closed. At 4 hours the temps begin to rise faster ... the fridge is around 50ºF and the freezer is around 26ºF ... which is warmer than I would like, but nothing dangerous.

But instead of sitting in the dark listening to the refrigerator run, you might also want to run a couple of lights and maybe the internet stuff, charge a couple of phones and probably watch TV for a couple of hours. That is exactly what I built my system to do, because during a hurricane I don't want to be stumbling around in the dark trying to hook up a generator.

With 5kWh of battery and a 2600 watt inverter I can keep a regular fridge plus a mini fridge running, plus a couple of lamps, plus all phone and computer stuff and a TV going all night and not worry at all about running out of juice. And I don't have to rush to get out the generator until the winds stop blowing and the crap stops flying.

My signature is a link that shows the basics of my system.
 

ktyv

New Member
Thanks for all the replies. Seems like an active and helpful community here. Some follow-up comments:

I did previously consider a wireless thermometer in the fridge, but figured it'd be a faraday cage. I just stuck a temp sensor on a shelf on the door and it does seem to be able to communicate with the base station. Surprising. And my base station has internal battery backups with local storage, so if the sensor continues to work, I will have a reliable way to record/see what the temp is doing, or did, in the fridge during an outage.

Another benefit of the battery backup over the generator is that I'm the only person in the household that can get the gen pulled out, started and hooked up. I'd trust my nine year old to plug an extension cord into a battery box.

Still seems like a big price tag for batteries and an inverter/charger. I'll keep thinking on it while collecting some temp data.

Keith
 

pollenface

Solar Addict
If the outages are a regular occurance you could run the fridges permanently from the inverter with a maintenance charger permanently connected to the battery.

I thought about doing that extact thing, all wrapped up in a nice plywood box sitting next to the appliance.
 
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