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Any chance a 400W continuous (800W peak) inverter will run any small chest freezer?

ecwashere

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May 16, 2020
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I'd like to be able to power a small 3.5 cuft chest freezer or similar from a Cobra CPI 475 12V 400W inverter connected to a yet-to-be-built ~13V battery bank. The freezer will be connected to AC most of the time and only connected to the inverter during a prolonged power outage.

Small chest freezers draw ~150W while running intermittently. The obvious hurdle is getting past the startup surge and working with a modified sine wave inverter. This inverter claims it has an 800W peak. I'm planning on using beefy and short cabling between the battery and inverter.

Has anyone been able to get any small chest freezer to work with an inverter with similar specs? I just want some battery powered freezing available so all my meat doesn't go bad and so I can still have some cold beer to share with the zombies.

I did see a thread here where someone failed to do something similar with a mini-fridge and a 300W inverter with unspecified max. I believe chest freezers are more efficient than mini fridges (mostly because the air doesn't fall out when you open from the top), but I'm not sure if they require more or less startup current.

DC chest freezers are probably quieter and more efficient but I don't think the price justifies them for my just-in-case scenario.

If it doesn't work, I'll invest in a higher capacity pure sine inverter and maybe just build a 24V or 48V system. But since is this really the only critical load I need to run, I'm trying to make it work with what I have.
 
MSW don't do well with motors. Net effect is a HIGHER current draw. Peak claims on cheap inverters are usually for fractions of a second where they aren't meaningful for the longer duration surge.

I have this little cheapo, and it easily runs a small air compressor.


Compressor:


I powered it through a 120W cigarette lighter port once, and it popped the fuse, so it's higher than 120W :)
 
Probably not.

It may well support "running" current. but will choke on the "sartup" current draw. Also, your freezers compressor may run hot, reducing lifespan, if you use a MSW inverter. I killed a Frigidaire running it for an extended period on an MSW.

I went through a number of inverter looking for a good match for a 10.8 cf refrigerator/freezer. I found some cheaper 1400-1500 watt inverters that wouldn't work. I finally settled on a Xantrex 1000 watt PSW. It has been flawless for 6+ years.
 
I appreciate the great advice.

I'll get the chest freezer soon because my freezer is getting full. I can test it with a 12V car battery and this inverter to see if it'll even start up. However, based on what you're saying, even if it does run, I shouldn't run it for long periods without a PSW.

I should probably build a 24V or 48V battery system. They inverters were so much pricier when I last checked.

...And yeah, per the manual, the inverter can handle 800W for 0.1 sec.
 
My new rig is getting a Xantrex Prosine 1800/24. I have a couple of them. I don't recall them being very much more expensive than the 1800/12.

The 400 watt msw DEFINITELY does have the capacity to overcome LRC.
 
:) I'll sell you the Xantrex 1000 that I have...... It does come with a travel trailer and pickup truck attached to it though...... :)
 
I would suggest Low Frequency SW inverter, it can handle inductive load well witk longer surge duration spec.
 
Normally, I would agree, but LF inverters tend to be less efficient and may have higher idle consumption. Given the anticipated surge, I'd just use a cheap HF PSW inverter with rated continuous output above the surge. 800-1000W in this case.
 
Bur for emergency during power outage is OK in this case I would think. HFPSW has surge duration of abou 50 milliseconds which is not much.
 
I would run a small UPS. Low-frequency for good starting surge, pure sine, and works autonomously if you lose power when away from home.

I bought this used UPS for $240 on eBay including two new 18AH AGM batteries. Can't get much more simple. Show and Tell. Make sure you get the XL model rated for continuous duty.
 
Edit. Oops - newby error - just read an 18 month old post thinking it was a recent one. Good luck with whatever you decided to do 18 months ago.


This is an on the fence kind of reply with considerations rather than a clear recommendation:

I am running a 5.3qt 230v AC chest freezer via a cyberpower cps1000e 1000va low frequency UPS with two 100ah 12v external gel batteries in parallel. Works well and I run it in UPS mode so batteries are on float most of the time but since I have had it for a few years I am in process of researching DC freezers too. I will share my thought process.

If you are starting from scratch then it is cost of DC freezer and battery charger vs cost of an AC freezer plus a beefy UPS with PSW that has external battery connections that can actually charge big batteries with the capacity to run it for your chosen power outage time and can handle the inrush current. For that kind of UPS the cost mounts up making the DC freezer a closer cost match.

I measured my cheap 5.3qt freezer inrush recently and I was surprised how high it was. By luck, not by design, my UPS always handled it. Now with hindsight that the rules of thumb about compressor inrush current are not always correct you will have some uncertainty unless you buy one that you can find actual inrush current info online. I also draw your attention to the fact my AC freezer compressor draws way more running current than the wattage on the motor, as wells as much higher inrush current, so again, depending on quality, you cannot trust published vendor specs.

@Delmar I like your set up and good to know your method with that UPS and fridge works.

Here is mine:

Running a DC freezer from lead batteries means no inverter sizing concerns and no bms sizing concerns. It becomes much more simple. You will need a charger though and you will be running your batteries in cyclic use vs float/UPS mode. Depends on what level of confidence you have on the info for an AC model. If you go DC route your only concern is low voltage disconnect and what settings the DC freezer has (vs a UPS LVD options for an AC freezer) and whether or not you need to add a seperate LVD but that applies to AC and UPS too.

Having said all that I still think AC freezer and UPS is better. You have two power sources, AC and DC, so if your objective is redundancy then AC and UPS is better.

Just need to find some certainty on the AC freezer actual running and inrush currents to choose/modify correct UPS and battery capacity. Some other forum members might help take actual measurements and share their freezer model details with you.
 
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