Using a Computer UPS as a Solar Inverter

steveo

100 kW
Joined
Oct 6, 2007
Messages
1,786
Location
Woodbridge, Ontario
Hey Everyone,

I'm looking at a cost effective way to get my home powered on off of solar energy. I'm almost where i want to be with parts.

So far i've accumulated:

9 X 195w Pannels
10 X AGM Deep Cycle Trojan lead Acid 85ah Batteries
1 x Solar Mppt 30 amp Controller (confirmed will charge 24v Lead bank.. not sure if it can do 48v I have to check the manual :roll: )
need to source a solar pannel mounting kit possibly.. or will mount to top of my shed roof :mrgreen:

as far as a ups to convert i'm looking at the Apc smart ups 1400va, (950w); however can easily modify them for capability up to 1500w i'm able to locate a couple on Kijiji locally and there are some youtube videos of guys modifying them for more surge current, one vid i saw showed surge current up to 3500w+ on a apc 1500xl unit :eek: .

I found a cyberpower pp2200 .. this is more powerful one stock .. 2200VA 1500w however i believe its 48v only which might be a problem for my solar controller..

they are both sine wave .. ones is pure sine wave.. the other just sine wave .. is that the same thing?

anyone out here on the es using a ups or thought of using one, would love to hear your experience

thanks
-steveo
 
Been there and done that - helped someone setup an offgrid system using an EATON 9130 (IIRC) which used a 300AH, 48V battery bank made up of 8 X 150AH batteries and 10 X 24V 200W panels from a grid connect system + PWM regs (cheapass)

Just had to remove the beeper. Any 48V UPS that can start on battery will work fine. Handled 3Kw load fine.
 
There is 'pure sine wave' and 'modified sine wave'. Get the pure sine wave. Modified sine wave is really more like a square wave with periods of zero voltage.
 
I've acquired a couple of nice smart Ups 1500 like shown here

https://www.amazon.com/Smart-UPS-SMT1500-1500VA-120V-System/dp/B002MZW5JU

Very nice/well designed units, however a lot of room for improvement/modifications.

Starting with the transistors, my specific unit has transistors that read:

94-4311
IR P427P
QNSQ

from one video i saw on youtube of someone modifying a rackmount APC 1500 UPS seemed to have used regular N channel Mosfets and added one capacitor of similar rating to what was on the unit already near the transistors. Also beefing up the traces behind the transistors to be able to handle continuous power longer.

So this begs the questions, can i throw in the trusty IRFB4110 mosfets and i'm good to go?

they have good current rating, fast switching, low IR

can someone confirm? I'll keep you all updated as i go :)

Thanks!

-steveo
 
94-4311 shows 55V, 98A, 8 mOhm, 97.3 nC Qg

There are plenty of choices with better specs for that one.

The other two aren't showing up in my normal searches. The numbers may be in-house.
 
fechter said:
94-4311 shows 55V, 98A, 8 mOhm, 97.3 nC Qg

There are plenty of choices with better specs for that one.

The other two aren't showing up in my normal searches. The numbers may be in-house.

Thank you Fechter, your awsome..

I tried searching and could not find the spec sheet for it. :roll:

Do you think some IRFB4110 would be safe/decent choice to use? I was thinking maybe replace all the fets in the unit with irfb4110 .. instead of just filling the empty slots.

http://www.infineon.com/dgdl/irfb4110pbf.pdf?fileId=5546d462533600a401535615a9571e0b

-steveo
 
Hey Fechter,

Could you please confirm the irfb4110 mosfet would do the trick here?

thanks!


fechter said:
94-4311 shows 55V, 98A, 8 mOhm, 97.3 nC Qg

There are plenty of choices with better specs for that one.

The other two aren't showing up in my normal searches. The numbers may be in-house.
 
steveo said:
Hey Fechter,

Could you please confirm the irfb4110 mosfet would do the trick here?

thanks!

By the ratings, they should be great. Should also reduce the heating a fair amount.
 
ill report back soon with some pics and results

thanks for your help!
 
so ive worked on modifying my inverter today..

on the agenda was removing the factory transistors and replacing them with some irfb4110 i had laying around.

i also replaced all the 20ohm gate resistors with 10ohm gate resistors to ensure they functioned well just in case they are harder to drive then the factory transistors.

i tapped the heatsink screw holes and found some screws that fit

i also beefed up the traces on the pcb with some 14 gauge solid wire plus some solder

i added some tiny caps also near the transistors
.. and i also added a 100v 1000uf cap on the battery rails

first test definatly the unit worked well.. however would go into overload protection anything beyond 1kw.. i then modified the shunt in the unit so it would see roughly 3/4 of the actual current and now it will finally runs my heat gun on full power without going into overload protection and shutting down.

temps on various parts of the unit after about 5 mins running where stable from 32 to 50 degress check at 1200w constant load.

my expectations.. transistor wise it should do 2kw+.. but i cant say that for the other components like some of the 10 gauge wires and ring teminals used in the unit from factory.... etc

im happy at 1200w.. but i will see how far i can go.. i will just monitor the temps.. i would love to see it run my hair dryer at 1800w continious!

with 1200w continious.. it should be able to charge my ev with the level 1 charger just fine... will try that once my solar syster is in order next year..

pics.. vids below

https://youtu.be/H838Zo8snX8

https://youtu.be/8IxC9SrEtbc


thanks
-steveo
 

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Nice job. Looking forward to see it in the end.
 
I've posted another vid on my YT

I have re-enforced the transistor traces best i can.

I've changed the power wires configuration a bit, a single set of silicon turnigy 10 gauge wires for now..

to help keep things cool, i will probably double// tipple up the battery wire inputs.

if it still runs cool enough, i will test at 1500w continious.. then 1800w continious.. for about 10 min bursts.

so far the 10 gauge wires at a constant 60 amps roughtly -- hit around 60-70 degrees

The transistor traces on pcb hit around 45-50 degrees
The transistor heat sinks where around 30-35 degrees
i forgot to measure the transformer.. but it wasn't at any alarming temps so far.. its good up to 180 degrees

-steveo
 
Hey steveo,

Thank you for sharing about the ups, it is definitely a great idea !

May I suggest you have a look at Dr Angel thread about homemade 18650 battery pack ? For the future at least...
Are your batteries brand new ?

Lithium is now much better to use for solar, and considering you seem quite skilled you may want to go this way. It will take time but will be rewarding.
Much better because
- Better charging efficiency, a lot of losses with lead acid esp at high level of charge
- You can use 90% of the DOD without damaging the battery. If you want to keep a long life span on lead acid, a dod of 30% is recommended. So 3 times less capacity needed for lithium. That would be about
- Available easily through computer batteries - however lot of work involved as you ll see in the thread.
- much better lifespan for lithium
- Very quick charging possible from potential generator
At the end they are a better bang for your buck even if you have to buy them new.

Anyway back to your design.

Have you calculated your needs ? I suggest you keep that AGM bank at 30-40% depth of discharge max for getting at least a good 3 years (1000cycles) of lifespan if new, and hopefully 5. That would be 12V/283Ah or around 3.3kWh available. Make sure that s fine, because if you are used to a "normal" house this will be a problem.

On a Sunny Day with 2000W of panels you should be able to produce 10 kWh, so better use as much energy as possible during the day, for instance charge your EV.

Regarding your 30A MPPT I doubt it is 48V compatible. If not you have a problem, 30A means at the output, which in 24V would be 720W. Connecting 9 panels with a 24V battery will likely kill your mppt. See manual for max power @voltage.

By the way, Investing in solar is like buying your energy for the next many years so it can appear costly at first. I don't think you will easily beat grid-tied subsidized electricity prices, but it may cost you less overall on the long term because being off grid tend to make you much more aware and careful about your energy use...
 
titooon2014 said:
Hey steveo,

Thank you for sharing about the ups, it is definitely a great idea !

May I suggest you have a look at Dr Angel thread about homemade 18650 battery pack ? For the future at least...
Are your batteries brand new ?

Lithium is now much better to use for solar, and considering you seem quite skilled you may want to go this way. It will take time but will be rewarding.
Much better because
- Better charging efficiency, a lot of losses with lead acid esp at high level of charge
- You can use 90% of the DOD without damaging the battery. If you want to keep a long life span on lead acid, a dod of 30% is recommended. So 3 times less capacity needed for lithium. That would be about
- Available easily through computer batteries - however lot of work involved as you ll see in the thread.
- much better lifespan for lithium
- Very quick charging possible from potential generator
At the end they are a better bang for your buck even if you have to buy them new.

Anyway back to your design.

Have you calculated your needs ? I suggest you keep that AGM bank at 30-40% depth of discharge max for getting at least a good 3 years (1000cycles) of lifespan if new, and hopefully 5. That would be 12V/283Ah or around 3.3kWh available. Make sure that s fine, because if you are used to a "normal" house this will be a problem.

On a Sunny Day with 2000W of panels you should be able to produce 10 kWh, so better use as much energy as possible during the day, for instance charge your EV.

Regarding your 30A MPPT I doubt it is 48V compatible. If not you have a problem, 30A means at the output, which in 24V would be 720W. Connecting 9 panels with a 24V battery will likely kill your mppt. See manual for max power @voltage.

By the way, Investing in solar is like buying your energy for the next many years so it can appear costly at first. I don't think you will easily beat grid-tied subsidized electricity prices, but it may cost you less overall on the long term because being off grid tend to make you much more aware and careful about your energy use...

I agree with you on the lithium batteries, I hope to one day do this with A123 Cells. I have some 8p12s modules that i can recycle to eventually build a full pack, however at this time i acquired this lead acid battery bank, it is still in good shape and they are the proper AGM Cycling battery from Trojan. I need to read into the spec sheets to see there details, i'll try to find that out shortly and report back. Will note to self 30% dod! ..

To bad i can't set the cutoff voltage via the UPS.. and i'm not sure how i can change the cutoff/modify to ups to do that... I also need to test the voltage the ups will shutdown at... I intend to keep the batteries juiced as much as possible. I will even consider charging the bank at night (off peak) for a couple hours if nessasary, i can do this by keeping the ups tied in with a simple timer.. I think its charger is only 250w per ups unit.. . but if i use 2 units tied into the 24v back -- we can get a 500w charge rate for say 4 - 6 hrs a night just to boost soc !.. then in the day time solar can take over and grab a couple of free kwh!

I haven't actually calculated my needs per say, some of this equipment i've acquired over the years and i hope to make something that will meet my needs. Even if i have to charge my ev at night and run my household during peak with the solar system, that is my main goal.

reg the solar controller.. not my preferred controller.. it was something i had kicking around and wanted to use.. It should charge 24v bank fine.. how much current it can take at a given battery voltage i don't know and have not investigated that far, i might be limited there. I know the solar controller can charge a 24v bank as 24v pannel input or 48v pannel input.

i agree with you here for sure:

"By the way, Investing in solar is like buying your energy for the next many years so it can appear costly at first. I don't think you will easily beat grid-tied subsidized electricity prices, but it may cost you less overall on the long term because being off grid tend to make you much more aware and careful about your energy use..."

I had a much more advance.. higher cost system which i purchased and resold just because it was just a monster of a system that i don't really think i needed.

-steveo
 
yes a quality ups makes a nice solar inverter.been doing that here last 25 years.
i saw the modding being done to the mosfets,shunt,ect.
i would not bother.
see the mfr uses that same board for the whole line from 1kva to 3kva.
and populate to suit.
all you will do is blow it up when the undersized transformer hits core saturation.
the larger units have a larger transformer.
i use a larger unit than my worst case load and add a fan if it does not have one.
the few that i have had to repair had dried out caps.i replaced every electrolytic in it.
good for another 25 years.
never a silicon failure.
old apc and best power units in metal cases is what i use.
if its in a plastic case forget it.
most dont have proper heatsinks and are ready to melt down at end of battery capacity.
look for large commercial units with expandable battery banks.
virtually indestructible.
 
had some compaq branded 3kva 48v units that were great.oem is deltec.
saw some recently on govdeals but you have to buy by the palletload.
dark startable too.
thats important when using them for an inverter.
 
Hey Everyone,

I just wanted to update this thread her..

i did manage to successfully series 2 of these ups to get 240v+

I did the same thing as knurlgnar24 here on youtube

https://www.youtube.com/watch?v=THh_2ssHWL0

My mod was slightly different though, Instead of the ADC0838 chip used in his ups, mine uses TLC0838C chip

where as he added 5v to pin 2 .. my ups was slightly different to mod.

I had to break a trace between pin 2 and 9 that where connected .. pin 2 is DI ... pin 9 being "REF"

these 2 pins originally ran on about 4.94v so adding 5v off the regulator did not seem to do anything.

when i added a dc to dc converter of the 24v battery bank, and varied the voltage between 4.5 - 5.5 to pin 9 of the chip "ref". The ups would vary its ac output voltage up to 138v .. and down to 106v ac roughly. higher the voltage the higher the ac output went. When i set pin 9 at about 5.5v.. i got 135vac output, it disabled mains battery charging capability but keeps sync to main capability enabled just like knurlgnar24 did in his video.

The only difference i noticed is my output voltage increased with the mod but knurlgnar24 240v mod did not vary his output voltage.

I did series the N and the L wire of each ups.. the slave ups that has the mod was plugged into the master ups.. and i got output at 255.

I guess the question remains.. can i have this work but have even 120v output on both ups?



Does anyone have any idea if i bought a 240v ac output ups .. if i could modify it for 2 lines of 120v which i can still series for 240v?

I have my eye on a apc 5000 240v ups unit .. that has 240v out.. but also has transformer that i can add to reduce voltage down to 120v...

The idea is i want to be able to mount it directly to my north american home electrical panel!

thanks
 
spinningmagnets said:
My work uses 24V UPS's on quite a few devices, are there any 48V units that anyone can recommend?

I just picked up 4 monster 2200xl Apc units that are 48v units, i believe they are rated for continuous use at 2kw. I'm sure peak is a bit higher.
With added mosfets, i'm sure 3 kw is possible continious..

I'm not sure yet how to series them working at 240v, but i'm working on it
 
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