Smart-UPS 1500 turned into... a 12V inverter?!

In this video, I show off a 24 V Smart-UPS 1500 that I turned into a 12 V inverter.

The modifications required to do this involve gutting two UPSes and modifying a single resistive divider on the mainboard to fool the processor into thinking that it's got a 24 V battery connected.
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[jordanadams]

Sweet project, you certainly put more effect into it than I would! I have a set of 4 APC 1500’s (Various models but all the same style floor unit) that I intend to connect to a 24V LiFePO battery bank to be used with solar to recharge them off grid. If ever needed, a single one of the UPS’s could be connected to mains to charge the bank (Not 100% on that not cooking the UPS’s battery charging circuit due to overcurrent though)

[kiskiller]

wow i didnt think of tdoing that modification, but i like the 24v system since it uses less amps soo cheaper cables and everything... but a 12v unit is alot more versatile thanks for the video!

[koryyyy]

I'm a middle level electronic hobbies, and I laugh at "little simple modifications". hahaha Thanks for the video!

[RockMan-txcn]

Hi FFcossag,
Nice work. I would like to convert an APC Smart UPS 1400 (White Color) to an UPS that only takes one 12v battery. From your description, it seems to me that your changes solve 12VDC to 120VAC and the control part to take a 12V battery. How do I take care about the battery charging part(charge 12V battery and prevent from over charge)? or does your modification by adding the resistor already take care of the charging part? Thanks.

[ahmadkhalidhotak]

I have APC smart-ups 1000 model, with the identical second transformer, where should i connect the parallel 56K resistor on this specific mainboard ?

[leviahamefula]

Wouldn't it be easier to use a voltage doubler to step up the battery voltage to 24v?

[toobglued]

why would you want to cover to 12 v system when it runs cooler on 24 .. half the current. ?

[toniodebono]

Hi, I have a 24volt ups and I am trying to use it as an constant inverter using 2x 12 volts car batteries but the ups only last for 5 minutes and switch of automatically, I've checked the batteries and day are supplying 25.5volts on load, does the ups has an internal timing?and if so can I modify that or eliminate the timer? Thanks

[DJTrainRk]

Oh man I love that inrush on your 2nd startup!

[gondorwaller]

i am currently in the process of setting up a solar system, and am debating whether to arrange the batteries for 24v or do this mod. according to my understanding, 12v will use double the amps and waste more energy as heat in the wires and transistors, while letting the two transformers run half as hot as one would. that would let you use better mosfets and improve the low voltage side without worrying whether the heart of the machine, the transformer(s), would burn up, letting you really reach its maximum rated potential. the alternative is to put the mosfets and two transformers in direct parallel, essentially overrating the power components, and let it run at 24v as intended, gaining increased efficiency while easily reaching its max rated potential and being reliable. another is to leave them as they are and do what you can to balance the load between them so neither is pushed too hard. what are your thoughts on this?

[tuyenphanminh]

Thanks! Anh What's about UPS Santak 1KVA CK1?

[TechnicalAlrounder]

How to check gate drive of this ups, sir in my apc smart 1500 ups gate drive of +ve chennel is missing results no output how to repair this problem please help me.

[Attohertz]

Are these circuit modifications applicable to the SMT1500 model? (USB and rj45 instead of DB port)

[richmadrid]

Hi FFcossag, can you please tell us how and where did you connect the wires of the exhaust fans inside the Smart UPS?
Also what are the mods that you did to make it run cooler and more efficient?

[DoogieLabs]

Do you think it would be possible to use two transformers with the low voltage side in series and use a 36v battery bank?

[deansmith]

ok i added the 56k resistor and will add a 1-2 ratio transformer, i have NOT ADDED ANY MOSFETS OR CAPACITORS . Will It power on ?

[basilkasimi]

Is ups safe for fridge use or freezer if converted to an inverter

[spongygryphon]

This is really cool and interesting research, thanks!

[kamaliasc]

hello,
i have a smart UPS 1500, i use it as a solar power inverter.
it works for 8 hours and then it turn off.
(no overload)

i should re operate it again at every time.

is there a possibility to modify it so that can work as a solar inverter with pure sine wave. (working without stopping) ?

[uxwbill]

This sort of redesign is exactly the kind of thing I'd like to understand better.