UPS mod / hack - hook into car as an inverter

[electron]

Good morning,

Has anyone used an UPS in a car as an inverter for AC power?
My thoughts were to wire directly from the 12v battery to the UPS with a fuse inline. I am not looking to plug the UPS into the wall while hooked into the car.

Can I leave the original battery from the UPS in circuit
Recommended Fuse?
Disable buzzer or change to LED indication

The UPS is a Cyber Power 825AVR, max load 450watt

My project idea anyhow, as I have a long long road trip and would like to run a couple of AC powered devices.

[alm]

Can't say I ever tried it, but I would expect an off-line UPS, especially a cheap one, to overheat if you run it for longer than the original battery would have lasted.

[madires]

Has anyone used an UPS in a car as an inverter for AC power?
My thoughts were to wire directly from the 12v battery to the UPS with a fuse inline. I am not looking to plug the UPS into the wall while hooked into the car.

If the UPS is powered by a single internal 12V battery it should work.

Can I leave the original battery from the UPS in circuit
Recommended Fuse?
Disable buzzer or change to LED indication

I would disconnect the internal battery. The fuse could be a 40A slow blow. And disabling the buzzer is a good idea (maybe with a simple switch).

The UPS is a Cyber Power 825AVR, max load 450watt

My project idea anyhow, as I have a long long road trip and would like to run a couple of AC powered devices.

As alm already mentioned a small UPS might get quite hot if running for a longer time. If you don't need sinusoidal AC you could also use one of those cheap inverters.

[electron]

Thank you for the insight.

Would it get hot if running lets say at 25% capacity?

example usage would be, 1 string of 50 LED christmas lights, cellphone charger, camera charger.
second usage, PC computer to download camera photos, and maybe send an email should there be Wi-Fi. (17minutes normal run time for this setup on original battery)

For longer run time, would a fan or two help?

I have access to an older style UPS, same watt, just not as efficient, but the cover opens up to the air and I could install a fan much easier.

[Stonent]

It's an idea but inverters are usually fairly inexpensive.

[ejeffrey]

Some UPSes won't power on without the mains supply voltage present.

[eevblogfan]

Hey

the UPS is build like SH**T .

1/3 of the power capacity is reqired in order not to harm the transformer . as for the switching fets .. if they run hot .( >80C on the outer body )  take some CPU heatsink and mount hem on it ...

at 1/4 of the rated capacity it will run either warm or hot . but I don't think you'll demage it ..

Yes I did it ... twice ..

one was 1200VA one . it was loaded with 700W load . and after 30 min.... there was smoking transformer ... after opening it up . I saw 400W core ...

the secoand time . I was smart ... firstly saw the power of the internal transformer . this time it was bearly 90W .... and on the UPS there was written " 500VA"  at PF of 0.7 .... that's 350W . witch is 3X more than the stupid 90W it can hold ... GEEEEEEEEEEEE 

I used it for only 100W load and it hold for 2Hrs ..

 

[Psi]

Can't say I ever tried it, but I would expect an off-line UPS, especially a cheap one, to overheat if you run it for longer than the original battery would have lasted.

I can confirm this. I added extra large batteries to my UPS and it started to smell a bit burny after 40min of running on battery. (original batteries only lasted ~10min).

It didn't stop working, just yeah, smelled quite hot. I cut some holes and added a few fans and it was fine after that.
But yeah, it needed the mod to work continuously.

[amyk]

example usage would be, 1 string of 50 LED christmas lights, cellphone charger, camera charger.
second usage, PC computer to download camera photos, and maybe send an email should there be Wi-Fi.

Except for the LEDs those are all low-voltage devices. A direct step-down from the 12V rail on the car will be far more efficient.

UPS inverters are built down to a price, so they are not going to be very efficient (and the overheating problems further point to this).