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V7 Rackmount UPS
#1
I was looking at this UPS to repurpose as an inverter for a 48v system. Does anyone know about this brand? It seems pretty cheap for the type.
https://www.ebay.com/itm/273956588790

I was also looking at this one:
https://www.ebay.com/itm/APC-Smart-UPS-S...3820383434

I'm looking for something in the 1500w-2000w 120vac range. Will be powered by a small 4kwh battery. I'm probably not going to the use the built-in ATS as this is planning to be an off-grid circuit for a specific purpose but I haven't ruled that out as an option so it would be nice to have.
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#2
The APC models are built really well. They can be easily upgraded to handle a bit more continuous load by adding in the extra parallel FETs. I have the 2200 floor model, and AveJoe uses the 2200 Rack mount model for his powerwall.

I am unsure of the V7 unit.

Please keep in mind that a UPS will waste more energy during inversion than a standalone inverter. But, if you can get a good deal on them, go for it. They could be a stepping stone to a bigger system down the road.
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#3
I run several APC UPS(s) - a pair of APC 3000 and a couple of APC 1500(s). I use DIY 7s7p 18650 lithium-ion as replacement batteries for the standard lead acid. They charge the lithium 7s battery replacements to around 27.8v (3.97v/cell) and discharge down to 21.6v (3.08v/cell) before UPS cutt-off which is pretty low but safe enough for well-balanced packs.

My APC 1500(s) idle burn 40w/hour for each APC - I think the 3000(s) burn a little more like 50w/hr.

Not sure of inverter efficiency.

It was also my idea to use these as battery bank backup for power outages - i.e. grid maintaining the charge and APC giving 120v output on power outage backed up by large 7sXp pack(s)... but then I went bigger with panels and charge controllers and outgrew that idea.
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#4
Hmm.. That seems like quite a bit of idle power burn. Maybe need to reconsider.

I was originally looking at the AIMS 48v 1500w inverter. They list their idle drain at .5 amps so if I did the math right it would be idling at 27w (15s li-ion battery 54v nominal)

I have about 4 kwh of batteries and I will have a 2s2p 305w sunpower solar feeding the batteries via a victron 150/35 smart solar mppt.
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#5
I think mike has calculated how much his draws. Maybe he'll comment about his. Hey Mike!!!! Tongue
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#6
(10-24-2019, 01:14 AM)gpn Wrote: Hmm.. That seems like quite a bit of idle power burn. Maybe need to reconsider.

I was originally looking at the AIMS 48v 1500w inverter. They list their idle drain at .5 amps so if I did the math right it would be idling at 27w (15s li-ion battery 54v nominal)

I have about 4 kwh of batteries and I will have a 2s2p 305w sunpower solar feeding the batteries via a victron 150/35 smart solar mppt.

OK, if you have a solar panels / charge controller then you may not need to run the inverter 24/7.   In my case, I use AIMS but I turn it on when the batteries are charged to a certain level and turn it off when the batteries drain down to a lower level.   So I don't have any 'idle burn' associated with the inverter because its turned on (automaticallly) only when it will supply power.   

If your feeding in grid (using inverter as the charger and/or ats) and using the battery/inverter as power when the grid goes down - then who cares about a little 'idle burn'.  If you running an off-grid system with solar panels / mppt, then yes I can understand avoiding 'idle burn' but as I mentioned above, I get around this by only turning on the inverter when it's needed.

Can you describe your scenario in a bit more detail?
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#7
Since I rent I can't do any permanent modifications to the house. This stuff is still very interesting to me so I like to play around and learn. I am building a small off-grid circuit for my shop to run some computers, internet/networking items and small electronic items I want to keep online. We usually get 10-20 power outages each summer due to monsoon thunderstorms. The outages are hard on some things. I'd also like to be able to run my desktop laser cutter when the storms are coming through. That pulls less than 1000 watts. I need to measure that exactly. The laser does not need to be on solar always.
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#8
(10-24-2019, 01:52 AM)gpn Wrote: Since I rent I can't do any permanent modifications to the house. This stuff is still very interesting to me so I like to play around and learn. I am building a small off-grid circuit for my shop to run some computers, internet/networking items and small electronic items I want to keep online. We usually get 10-20 power outages each summer due to monsoon thunderstorms. The outages are hard on some things. I'd also like to be able to run my desktop laser cutter when the storms are coming through. That pulls less than 1000 watts. I need to measure that exactly. The laser does not need to be on solar always.

OK, let me try to help so you can think thru options that might work for you.

Power comes from 2 basic sources:
1) Grid - constant and unlimited
2) Solar - variable and limited

Batteries store power for 2 basic purposes
1) As a backup to a power outage - they charge up to float value and sit there waiting to be used in power outage
2) As part of a Solar system - they charge up and discharge down and act as a buffer to supply limited 

Some basic options:
If you go APC UPS route - then its easy to imagine Power #1 and Batteries #1.    The grid comes into APC and keeps your battery bank charged waiting for power outage, at which point the APC automatically starts delivering power from the batteries to maintain 120v.    This what APC UPSs are designed to do.   APC UPSs are not designed with solar power input in mind.

If you go the Solar route, the power comes in from the Solar Panels -> Charge Controller -> Battery bank.  To get 120v out, you hook an inverter into the battery bank and it will create 120v.   However, if you draw more in 24hrs than the Solar Panels can produce the inverter / 120v will 'stop' at some point.  

Recap:
There are mixed options that combine Grid + Solar power inputs... but they are more complicated than the basics (above). 

I would not focus on 'idle power' as the large issue until you figure out your overall design.  For example, an AIMS inverter (and most others) are only 86% efficient in producing 120v from a battery.  That 14% loss may be as much or more as the 40w/hr idle burn of an APC UPS

It is fun! and I would pick a simpler option and just get started and start learning how things work.  If you're like me, it really helps clarify things in my mind to do some hands on!

If you can describe a specific choice you want to explore - e.g. Say off-grid, Panels -> Charge Controler -> Battery -> Inverter and perhaps share the equipment model/sizes - then a more specific discussion can be had.
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#9
Adding:
You can use the UPS as the inverter with the Solar Panel -> Charge Controller -> Battery Bank -> UPS setup. The UPS doesn't have to be charge controller. Though, it will try to charge if the battery voltage is too low. But, with server grade UPS's, you can use the PowerChute software to change the voltage triggers. Check out AveRageJoe's video on this as that's what he's done with his.

Note, Joe doesn't use the UPS to charge his battery bank, but does the above as I mentioned, using the Solar Charge Controller.
Proceed with caution. Knowledge is Power! Literally! Cool 
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#10
This has helped me out quite a bit. It has forced me to reconsider what I am building!

I think I am going to go with a couple simultaneous options.

Main System: Solar (~1200w 2s2p sunpower 305w) -> victron 150/35 mppt -> 4kwh battery

Running off this will be an intermittent AIMS 1500w inverter for on demand use. Less efficient but still able to power what I need. Power goes down? Fire up the inverter and run an extension cord to what I need to power and back in biz.

Also running off of this system will be a smaller rack mount UPS. I'll be looking for something in the 500w range. Everything plugged into the UPS will run on grid power day to day but then can run off the battery bank that is solar charged when the power goes down. I need to power the security cameras, internet and some other lower power devices. <200w of stuff at any given time.

Then I get to build some stuff and learn and get some benefit out of it. I like to be prepared so this will be nice to have a small backup system. The long term plan is a big solar/battery based system to run all the household items. That is a few years away at the earliest.

I have a small 450wh 12 lifepo4 power pack I'm finishing up and then the next is a larger 7s li-ion 7s40p portable pack. Definitely lots to tinker with in between my laser cutting.
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