This is great that someone thought of doing this. I have 4 similar units that I thought about using like this. I thought about the master-slave config as well, but was not experienced enough to modify the units to "stay-on-battery". My idea was to create an external master signal that is fed into the mains input to fool the UPS units into staying on battery while synching to that master signal. I would assume a simple 60hz signal generator circuit at the appropriate voltage might work. Have not tried this yet, but would be interested in your thoughts. I agree that the series setup would work best from a failsafe standpoint. In my case, the UPS are only 240v output. Consequently, I have a pair of 3kVA transformers on the outputs to give me 240v with a center-tap neutral for the 120v circuits.

this was a very well thought out and clever modification, thanks

The only 240 appliances I have are the dryer and the range...however I hadn't even thought about the heater blower motor until you mentioned it......I need to check that! My system is mostly for power outage type situations so it wont get much use (i hope). My plan was just to flip the breakers off to prevent accidental damage if they were turned on. Very cool series and I look forward to more!

Very nice work. Thanks a lot for sharing this priceless experience with us!

Great work, been watching your APC vids and learning a lot. Just one criticism, the jumper wire between - and + terminals in your battery pack needs to be the same size as the main battery leads.

Nice! If it is possible - you could develop and patent a unit to do this (synchronize multiple UPS). I'm sure it would be in demand. I don't really have a problem with paying for higher capacity units. I have a problem with the batteries being short lived when the unit as a whole is fine.

Very nice info to have, awesome video. In the video you said 2 legs of 120 and 1 of 240 like the house mains but in a comment you said a step down transformer is needed for 120, which statement is true. I would like to do this to have 120 from each ups but the option to use 240. Thanks again, thumbs up!!!

Very nice! Those 2200s seem to be much less common than the more pedestrian 1500VA and lower varieties so I used what I could get without paying big money for them. I didn't realize the XLs were rated for continuous, but I suppose with the add-on battery packs they almost have to be.

I had a similar plan in mind but ended up buying a 12V 3000W sine wave inverter instead. I made a 12V genset and acquired a bank of scrapped batteries to use. In all I have pretty much the same plan except that I wanted to be able to charge the batteries on gasoline and didn't need 240V power. Your 3kva units are much more capable than these 1500's and if you can figure out how to keep them in phase it should work well. Watch the no load battery draw though - it may drain batteries fast.

Very good question - unfortunately I don't know how to specifically disable the charging function. However my first thought is to lower the charger voltage to some level that is low enough for it to never charge. I'm not sure if this will have other consequences, but let me know if it works. Do a Google search for apc_smartups_battery_float_voltage and check out the first result.

Short answer is 'no'. Longer answer is 'maybe'. They are actually a few degrees out of phase so there would likely be pretty substantial current flowing between them causing significant internal heating. One could potentially add load sharing resistors to the outputs to ameliorate this but it would be only a kludge. I might try paralleling them in a later vid to see how/if it works. I hadn't intended to do this but I might demo that since more people will probably be interested too.

Please show us how to run them in parallel! I'm using two isolation transformers to do this and it's not as efficient as what you would propose.

Hi, I watched your 1500W conversion and the connection to the FET gates via those SM 20ohm resistors, interesting stuff. I'd like to multiple-up ups's in parallel (230V each) to double the current capability. Rather than fitting the extra FETs in the vacant positions, I have had this idea: 1. Connect UPS line inputs in //. 2. Designate master and slave(s). 3. Disconnect the voltage relay drivers from the slave and couple the slave relays to the master relay drivers. 4. Remove the slave 20ohm gate resistors. 5. Run a wire from one master gate 'spare driver' to the equivalent slave FET gate resistor pad on the slave PCB via the 'spare' 20 ohm resistors. 6. Repeat for all FET's. 7. Connect both units to the common battery 8. Fire-up both units to check that tho outputs are in phase. 9. Connect UPS ac outputs in //. 10. If it works, good: If it doesn't, it was only an idea! This would also save overdrive heating of the transformer etc. What do you reckon?

I have tried connecting multiple transformers to one unit and it does work, however the transformers I used were not matched well enough to actually increase the output in any useful way. For me I was better off using just the one transformer and increasing the cooling with heatsinks, fans, etc.

Can I use 120v devices on this?

Maybe you can - let me know if you find a place to inject a clock. I assumed they generated it internally in the control IC from the crystal onboard and you probably don't have access to it. They may also need to adjust the frequency for load transients, etc, and may not like a constant clock. Besides, these already have a 'sync' feature built in so I didn't see a reason to reinvent what was already there.

Can you show me how to do this using smaller APC ES550 Backup units? I have a bunch of these I would like to reuse in this manor.

Hi, very nice presentation - would it be possible the same way to connect just one UPS like this to act as grid-tie inverter?

Anymore videos on this?

Could you connect this 240V power inverter to your breaker board and be able to power your 240V stuff and both the phases without blowing stuff up

What model voltmeter are you using to show the sine wave?

Hello knurlgnar24 would it be possible to get some more load boost by adding identical output transformer in parallel?

Thank yoi for doing this! I was wondering if there is a way to connect 2 of these bad boys(for no good reason:).

THANK YOU! I've been trying to find a video about getting 240 out of a pair of inverters because I was thinking of running my hot water heater off of a battery bank. This video shows that it is possible!

I assume you've checked the fuse already... I'd start by taking it apart and cleaning it with shop air since it could be something as simple as spider turds causing a high impedance short. (shop air is also powerful enough to remove dendrites) Is there corrosion inside? Are the fan bearings good? (would indicate if it may have overheated) Does anything look like it got hot? Are any of the main power transistors shorted as measured by a multimeter? Those are the the things I'd start with.

Good video. I suppose it would be possible to use the FET drive from one of the inverters to drive the FETs in the other inverter at the same time, thus avoiding any phase shift and making it possible to parallel the inverters instead. Just a note, the mains in the US are not exactly 2 phase, but a center tapped 220, making 120 + 120.

since you have synced them, you can parallel them too?

what is you use only the boards, and you interconnect them at every level?!

I have 2 3000 watt APC ups' sitting around that I currently lug around when the power goes out. My initial plan was to follow this and add big batteries (the ups is 48 volt) and an interlock in the main panel, then run power during the night without noise and a dc genset during the day to charge. Power outages are usually less than 72 hours but do you maybe have a better suggestion? Just trying to run occasional things like the fridge, nat gas heat, and microwave during an outage. Thoughts?

I like your DMM with the o-scope on it. What make and model is it?

What if you merged the units together, so it has two transformers, and double the fets? The fets and transformer could go in the compartment where the batteries originally went.

Hi, nice video. I live in Italy, I have two smart ups 3000 with card 640-0735g rev 7 of 1996 and I would like to put in parallel doing your change, but having different tabs I do not understand where to make the bridge. do you have a scheme where you can figure out where to do it? Thank you anyway.

I was wondering how you were going to sync the output phases...brilliant! Of course this will only work with UPS' that have this feature (at least the slave must have it...the master just runs as it is)

Well the reference to the AC Mains may or may not be their so that can not be used for a clock. I was thinking about just replacing the on board clock with a standard clock to both units. ( parallel the clock on board ). Then start looking for the phase you are talking about on the board with a oscope. Once found start added a cap to shift the frequency and see what the output is. Just play with it...all I was thinking about doing.

Hello, I like the concept and the idea of using 240 volts, I have 2 APC SMX3000RMLV2U Smart-USP 120VDC, any idea about these devices if they can be connected together for 240v output and how? thanks

I'm a professional musician and general tinkerer. I find your explanations very easy to follow. I have an understanding of phase due to my musical background. Anyway, looking forward to an off grid project and plan to use a single UPS for less than 2000 watt load and your vids have been very informative on that quest. Also- I have a non working (left plugged in for a long time) Iota DLS 42-18 that was being used to charge my electric motorcycle and now sits on a shelf. Thoughts? B

I have a UPS, I want to connect to solar system which is 220v 2phase. UPS is 127v 1phase. Is there and transformer or an inverter that can change voltage and the phase to 1?

Thanks for the vid! Great info.

The phase tracking of this UPS is imperfect (about 5V as seen when measured from true 180 degrees) so it would work poorly as a grid tie. You could, however, generate 240 volts off of one leg of utility power and one off of battery power. I suppose you could power half of your house off of battery power and half off of utility power this way.

I was able to convert my older unit from 950wats to 1400wats ..I got a new unit 1400XL 1050 wats but I am not able to do the same thing to this unit I got to program mode. Then capital p I try plus or minus only getting no na can't get any further need your help

Test Question: is it possible to use a Pure SWI and a Modulated SWI from the same battery bank? One to provide sensitive electronics PSW AC power while the other providing Machinery the MSWI AC power-- such as a pump, mixer, etc.?

Waw 7 years now from this video and no new videos yet

Good stuff. Thanks for sharing.

Ok, i have a question. Would it be possible to connect the OUTPUT stages of both UPS to the same "control" ( ex. the signal that drives the input stage ) In doing so, both output stages will be in sync, and can be paralleled to achieve 3000VA from 2 1500VA UPS . I will try to do just that with 2 apc 1500 , but you seem to have more experience than me . Let me explain again : on UPS is the master, and the signal that drives the output stage is feed in to the second one, to drive the second UPS output stage. The original connection on the second UPS is cut , and with enough research , more can be connected to that "control bus" , and be perfectly in sync . What do you think ? Is it doable ?

dualing master USP's, yea especially if they are in close proximity, I'd like to see that battle on a 4 channel scope

How many real power you can drow with out damage the inviter

Hi, I have two identical inverters Sukam Smiley, capacity 1400VA /24v each. My load is 1604 that include 3 flat Tv, 50energy saver bulb of 16watts each and one underground water pump capacity of 1Hp (0.75) the underground lengh is 60mt. My one1400va inverter can not hadle that load, I was wondering if there is a way to conect this two inverters together to double power. please asist me on this.

Interesting! I hadn't thought of this. I just use two UPS's one for each phase to power my house, the problem with this is that I cant use my 240 volt appliances (not that I really want to) but this is turning out to be very informative.

Late reply here. I still need to check out your vids. Interest in building a charger or DC motor controller? Yes, absolutely. However off-the-shelf components will probably be much more economical. I'd love to work on an EV sometime though. I did some solar car stuff in College, nothing too serious, but it was fun.

Cool. What UPS's do you use for that? That's where I was eventually going with this but you beat me to it! I was concerned about powering the two phases out of sync because if I accidentally left something that runs on 240V on (like the furnace fan) it could damage things with the brownout condition, but I suppose not being careless solves that problem too!

Thats Incredible, I have noticed that you have connected both UPS to the same batter pack. How did you achieve that. Does it benefit in fast charging. What are the pros and cons of that.

Just taken the lid off my 1500 and done some measurements. As the battery module area is now surplus to requirements, I may have a go at fitting the guts of another unit into the space. This would give me the option of single unit operation or double, according to power requirements.

For my case, I broke connection from controller to mosfet and parallel control signal just from 1 controller but for two ups to make sure no phase shift.

Why could you not use a master clock and have both units running of the same clock, then just adjust one of the units to be 90 or 180 off of the other unit? So you could do split phase and run your 240 volt units? I have two of the 3000 units and I might take a try at that using a 10meg clock standard since the batteries are both bad in each of the units on mine.

iam pretty sure both have to mach 1lw each but you may draw twice the current. i did this with audio and placed a jumper at both speaker negative, and used both hot r.l to the speaker , made a center channel but it worked and dident blow anaything.

i know it can be done with an inverter, was not so sure with PC ups that's why am here:) anyway this is awesome, so two PC ups can be connected and use as one ups so we can get more power and use our PC for a longer period when there is power black outs, keep up thanks

Hello knurlgnar24. I have some of these, that are 2200 not 1500. They have two transformers, and a different CCA. Is there anyway you can tell me where I would put the jumper on these? I can send you pictures if you tell me how/where to send them. Thank you. P.S. are these units that you modified single or dual phase?

Hi knurlnar, I love all your videos of moding APC ups. Just so awesome. This video has a nice detail that I notice and would like to ask if your can reset it. That is the cold start default frequency. It seems that it is always at 60hz. Do you know how to set this cold start frequency to 50Hz as I use it for all stuff running on that 50hz frequency. Many thanks.

What I am wondering is how you are going to phase them properly. My suggestion is find the driver and carry those signals to the other, and you can do this by making one the master and the other the slave. Another way is to use one of those and a grid tie inverter. Also your drawing is off, as the way to get 240v is use a small transformer to connect the two, and then connect both neutrals to each other as 240v is both hots.

Hi I have 3 of these UPS 3000 's and they are running great on 56 AGM batteries of 100Ah in 14 groups of 4 //good for some 50 000 watts spare energie ! 1400 AH by 48 Volts ! they take only some 75 watts running on idle and do feed easaly a vacuumcleaner of 2000 watts no problem , now my question : do you know how to trick these SUA3000 to see the big battery pack and to charge at a decent level ( something like 25 to 50 or more amps since 14 00 AH connected is not happy with the small charge of a few amps as standard from these units ,I know there must be a possibilty with some programs and a serial connector to set up the UPS for a bigger pack of batteries then the standard sets , but do you know how to ???

Hi, nice vids. I've watched a lot so far. Question- I just ordered the Go Power 1500w inverter. I'm wondering- Instead of the kit inline fuse(Class T 200 amp) between the battery and inverter, could one use a 200 amp DC Breaker switch?

Is the input voltage 110v?

240V would be great for folks with well pumps or even large sump pumps ! I just finished watching this and the whole previous series and have a couple of questions : 1) Do you think changing all 16 FETs to a lower Rds ON (0.003?) would help the overall efficiency or at least reduce the temperature rise of the transistor heat sinks ? 2) Have you done anything about up-sizing the battery input cables ?

deep cycle and sweet complex mode

Could I connect multiple slaves to one master and get even more power

Good day. I need to thank you for your video,they are educational.Only one thyng don't like - QUALITY OF VIDEO I wish you all the best

It sure would be cool if most inverters came with a parallel port like with a lot of the inverter generators i saw someone use a regular generator and an inverter generator with the parallel option and combined them i have seen grid tie inverters that can do it but they are kinda expensive they have current transformers to check the system current draw and I heard you can use a grid tie inverter but if you are not using enough power one will blow

Greetings, I have 5 APC smart UPS 2200 units and a music studio I would like to power off grid with solar and perhaps these units. I dont have great access to my outlet atm but as a guess i'd say it runs 3000w and 4000w peak with all of my gear on. I'm not a electrical engineer and lack knowledge in this department. Can I connect a charge controller to the APC units? I'm thinking of purchasing a bunch of used 12650 batteries, restoring and building my own bank. I'd like this to be able to run 12 hour studio sessions. Would I be better off getting a pure sine wave inverter?

Is there a way of getting that back down to 120v?

Gotta be a way to get them to sing the same tune. In Phase Sync. Even if you to drive them off the same clock. If you have the Schematic There has to be a Clock source that can Paralleled and used be used by both inverters. Just be sure to Disable the one not being used.

So if I wanted to take that 240v 3000w output and separate it into two 120v legs 180 degrees out of phase, how would be the easiest way to do this?

Very cool, I will take peak tomorrow. I'm not well versed in circuit components, so please forgive my vocabulary ignorance. There are two components that look like fuses (1/4" diam, 2" long aprox) that had leads like resistors solidered to the board. The upper lead on one was severed probably from overheat. I'll have to send over some photos. On a different topic, any interest in building a charger and or DC motor controller for my LiFeP04 electric vehicle project? (see my vids) B

so technically i can connect two computer ups parallel to get more watt out put... i am worried if two ups are not identical and that may cause some phase difference ..(#AC 60HZ) if it was DC it wouldn't be anything to be worried about .. please reply...

If you are powering 1 UPS from the other, how would this double your total output?

hello there man great video I bean watching a lot of your videos as well , I recently got a APC SU3000RMNET I wan to take out two of the 110 outlets and make 220 is that possible I am not electrician so your suggestion greatly appreciated

Check my 'sync to mains' video for more info on the synchronization capabilities of these UPSs. They do sync to the incoming mains power on their own if it is deemed to be acceptably clean by the UPS. The jumper was to force 'run on battery mode' at all times even if the incoming power was in an acceptable range. If the slave UPS switches to running on 'line power', then POOF!! The jumper prevents it from doing so.

I know its an old video. Did you ever try out any 240v loads on this? How did it work out?

hi knurlgnar24, i have 2 pcs of APC SMART UPS 750 (SUA750I) 500watts, 750 VA its already 230VAC is it possible to make it a 1000watts using a 230V AC not a 460VAC? thanks

could you use the balanced split phase right out of the breaker box to power the units individually? You are forcing one to match the other, but if you powered each one independently from opposite hot legs wouldn't the phase be balanced just as any 240 outlet? I am hoping so. I need to give uninterrupted power my cnc mill. Hopeing to put two smaller economical units on it rather than the relativly expensive 240 volt out units.

current isn't additive in series, in series you are only getting the boost to voltage, current will be limited to the unit with the least capacity, Paralleling the output would give you a boost to load capacity. but your right about needing to maintain sync. Have you considered finding the local oscillator on the master unit and driving the slave with it. since most oscillator circuits use a feedback circuit seems it would willingly sync with an external source as long as the frequencies are close. which they should be give or take a hertz or 2.

Knurlgnar - this could be quite a break-thru for us off-griders. This SUA line of inverters uses the common battery voltages of large battery banks (24/48 volts) and you have now discovered a simple way to feed split phase 240 volts to a critical load panel of the traditional split phase circuit breakers. KUDOS!! Question - do you have a feel for how "balanced" the two 120 volt phases must be before problems arise? Can you experiment with this along with a long term load test to check reliability? I sent an earlier request concerning a SMX3000 - could you please take a look at it? Do you think the SMX line of inverters can as easily be "stacked" for 240 volt split phase power? These are quite efficient inverters as they seem to be transformer-less and rely on DC voltages at or above the AC output voltages??

Hoping you can help and respond..I have 2 X APC SU3000RMXL3U and wish to run them both from the same large external 48V Battery bank. Very similar to your battery connection in this video. Both units will charge the bank when grid power is supplied. I am hoping you can advise if this would be a problem for the charging circuits as they will be fighting with each other to charge appropriately. In a perfect world I would love to disconnect both APC charging circuits and add a external 4-Bank charger. Please and Thanks..Jeff / JC audio and light

Nice work wow! I have 3 1,200 watt inverters...they plug into to 120v (outlet) to charge the battery or plug into a car battery and use as an inverter: Dimensions Sensata Technologies Model# EV1200 Inverter input 12.6 VDC at up to 120 amps Inverter output power 120 VAC,60 Hz Inverter output 1200 watts transfer rating 12 amps Sine Wave Charger input 120 VAC,60 Hz at up to 12 amps Charger output 50 amps at 12.6 VAC provided with integral protection against overload. I want to set them up and get more watts out them,but don't wanna mess them up. Coyld you give an idea please?

if the slave truly syncs to the master wouldn't it sync in parallel as well as series ??

If slave UPS is synchronized with master UPS, why can't I run those UPS in parallel mode ?, instead in series I have multiple APC smart UPS with 220v 2700w capacity, I plan to run it in parallel... So I can get 5400w capacity

If they sync to the phase of the outlet, then you can easily wire them in parallel. If you wire them in parallel or series it doesn't matter... the phase still has to match.

Could you run the 240v into a 100amp power box and then make 120v and 240v lines. Just like it does in your house from the power company. I ask because I have a trailer that I have solar panels charging car battery. Right now it is running a car alarm to keep people from braking into it and stealing my tools again, but would like to start using it to run my tools. I have a compressor and a welder that run off of 240v and a plasma cutter that runs off 120v or 240v. Then I have grinders and saws that all run off 120v only. So I would like to get (2) 5000 watts inverters put them together and run all my tools without having to run my loud generator of course I would get a few extra batteries to store enough power to run everything.

Hello! I have 2x APC Smart-UPS 2200VA RM 2U LCD 120V. But I live in Europe so I need 220V. Also, I am off grid so I use a fotovoltaic system. Is there any chance to modify the output of a single APC to 240V? Thank you!

I use SUA2200RMXL3 and DLA2200RM2U . Both are rated at 1960 watts I believe, but the XL is rated for continuous output and allows up to 10 external battery packs! The bad news for me is that they both are 48v systems, so to power them I use 4x 100ah deep cycle AGM batteries in series. Since I wasn't even considering trying to sync them I decided to go the low tech way and use one to power each phase, with the understanding that I would not be able to use 240v appliances.

This is very interesting. I have two 3000 watt APC smart tower upses. I have connected external battery cable, and removed the internal batteries. The plan is to install an APC UTS10BI universal load shedding transfer switch. Each side of the 240 volts could be powered by one 3000 watt smart apc ups. This transfer switch is connected to everything but the stove. This means all the connected loads are 120 volts. The stove is the only 240 volt load in my apartment.. All this being said, it would be cool to have a true 240 volts going to the transfer switch. I might want to use the stove or buy a 240 volt freeze dryer, or some other made up reason to justify doing this. Have you though of using a transformer to invert the signal to sync the slave inverter to the master inverter? This would put the inverters out of phase by 180 degrees, using low current. If this worked then in phase and inverted phase transformers could be used to stack smart ups's. This could be a great cheap way to have modular fast backup power. The world seems to be full of 3000 watt apc upses with dead internal batteries that are cheap or free. I have UPSed my apartment. 6,000 watts of power from two 3000 watt upses and 12,000watt-hr of battery is lots. The building supplies heat during a power failure. Canada does not get very hot so I am not required to provide heating or AC. At some point, I will add some foldout or removable solar to the balcony. Asking you sure beats taking everything apart. eTutoring.com

i have a stupid question , can i and is it safe to use a ups to charge another one?

hay your video"s are so informative the only time i have to watch is late at night . i have a smart ups 950 running watts. on the font of the unit its label 1400. i saw your video that you did on the 980 ups up grade. Do you think i could do the same to a older 950 . inside the unit look the same as the you upgraided

What about running in parallel

Interesting project. My only criticism is that in your sketch, - IF - you're intending to show the waveform at the 240V output leads (referenced to the common lead tying the outputs together), your explanation of the phase relationship is backwards, although you do explain it correctly later in the video, re house wiring.

Good Job

that's pretty nifty it be nice if it could run a 240 volt Air conditioner on that set up. since I do have two of these types of unites I have the tower version but should be able to do the same thing. I wonder what would happen if there is and in balance between the two sides. split phases. I have to say prettty cool. I also like to try them in the other configuration were its still just 120 volts. I guess you couldn't plug it in the wall as a APC any more since its only 120 and still use it as a APC with this configuration. or will there have to be other changes to either way this is cool like to see more on this set up, of what it can and cant do.

" I only want one unit to charge the batteries" If you don't want it to charge then it's no longer a ups, it's an inverter, and to make an inverter out of a ups you only have to not connect that respective ups to a 120/240v source. To specifically disable the charging mechanism but keep the ups fed with voltage from the mains it will probably involve damaging or taking out some part of the charging controller or just disconnect the charge wire, some ups's have independent systems.

interesting. I love intelligent KZfaqrs by the way... I troll the dumb ones... in which case they troll me back, and then I ignore them because I got my reaction from them which was all I need.

3 Bissell employees disliked this video LOL

Love it