12VDC to 220VAC Inverter

[Dieselsmoker]

I'm just sharing this in case someone finds the information useful. I told a couple of people about what I did and nobody seems to have thought of this....

We are going away over the December holidays to an off-grid farm on the coastline. There is solar power for lights - but thats about it, so I made a 220V 360W Inverter using an old PC UPS. We can now charge phones and operate the jukebox and so on by connecting this to the solar battery. I've seen these laying around and maybe some of you can also breathe some usefull life back in these units.

The conversion is easy:
Dump the internal 12V 7Ah gel battery
Desolder and remove the piezo buzzer (if applicable)
Add leads and crocodile clamps to connect to the deep cycle battery. (Extend the leads that connected to the internal battery)
Remove or disconnect the mains input port - optional, but I removed it since the charging circuitry will probably eventually go up in smoke if someone tried to charge a big battery with it...  in theory it should work as long as it doesn't overheat.

Since I'll be vastly exceeding the original designed duty cylcle with the big battery, I also drilled some additional ventilation holes and added a 12V PC fan to keep things cool.

Here I'm testing it with a 220V 150W fan that was handy. It works great!

[Dieselsmoker]

I have a couple of converted UPS units I did this to years ago.

I expected nothing less from you glort

A while back all the ups'es at work were changed out for new ones because the batteries were dead. Why the bateries were not just replaced is something for another topic - another day.... I kept two of them in my office and recently I learned that the rest were scrapped!! I nearly fainted - but luckily I saved the two... It freaks me out to see how things get wasted - especially in big companies where item value is expressed in %. When your maintenance budget runs into millions, nobody worries about a couple of ups'es.

I used some APC brand  and they have been great.  Taking out the buzzer is a great idea. Bloody things never seem to burn out no matter how many days they sit there annoying you!

This sound this particular model makes reminds one of a heartbeat monitor. We used these in the office at work so imagine how bad it is when 10 of these start beeping at the same time!!   

There are a couple of things with using these power supplies as inverters.....

Firstly, it's best to get " Cold start" I think they call it capable.  Ones that will start from battery power alone. My small APC's need AC power before they will fire up. A small inverter takes care of that but the inverter doesn't really like it so I disconnect as soon as the UPS wakes up. The bigger units all seem to be cold start so will fire straight off battery power. 

I have both of these types. I was lucky with this one that it can cold start as there won't be any mains power available to get it going. I guess one could modify it to be permanently switched to DC input. There is a very definate loud click from a relay when it switches over to DC power, so maybe therin lies the answer... 

Another and sometimes not easy thing is to see what battery voltage a unit needs. I got a few brand new Eaton UPS with good output only to discover they were all 96V input.  Even with small batteries that gets expensive to buy but I wanted to use car batteries for work in the field so they got onsold.

I would leave them charge capable. Connecting them to big batteries ( as In N200's) does Not hurt them at all, just takes a long time to charge the battery but they do a good job. They will float them nicely once they reach full charge and if you go into the setup through the computer attached to the UPS, you can ajust the voltages for  charging, upper and lower cut in and out limits and other things.

The beauty of the UPS units is they output a very clean and well conditioned supply that you can run anything off as long as it does not over load.

Good plan with the charging. I'll play with it and see what it does. It might just turn out to be the trickle charger I need to keep the John Deere battery alive 

[Dieselsmoker]

  enjoyed the video and the write-up.
You nailed a couple of points squarly in your video - I had a good chuckle 
Thanks for sharing!