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Should I get a giant UPS for cheap?
Advice please: Is a free APC Symetra LX worth my time? 

My scenario: I live in a remote area, any hint of a wild fire, the Utility Co cuts our power (need it to run well), one fire caused heavy damage to the power infrastructure and we had no power for 3 weeks, so now they cut power just if the wind blows - last summer we probably did over 25 separate days of outage, typically 1-2 days continuous. 

Goal: Potentially run long term (weeks) on solar/battery, even if at reduced usage, just essentials like fridge/well/limited lights.

I am in the process of capacity testing 30,000 1AH LiFePo4 cells, I have 10kw of solar panels coming next week, I have a Solar Edge 10k GT Inverter, and a SMA 7k (run 2 in case 1 dies).

I work in the IT industry, and we work on electrical automation stuff, and my family was in the construction industry, so I'm adept at most anything I need to be.

Client is liquidating, they want this UPS hauled off tomorrow. I have nobody to help on such short notice, so I might have to pay 1-2 guys $100-200 to ride along and help me yank the 4 batteries out of the tower and lug it over to the truck (~650lb) and unload at my house. I dont even know the exact model (they werent swift enough to send a photo of the back label, it could be anywhere from a 4kva-16kva tower, I imagine it is a 4-8.

If its the 8k, that is 6000+ watt sustained power handling.  My well is a 3/4hp 220v pump, I imagine if I add an additional startup capacitor to the motor, this UPS would not care.

I have already setup a 12v Lifepo pack in a small UPS, and was able to nearly triple the runtime over a brand new SLA pack, and the charging range would be well within the happy range of the Lifepos, they would most likely last 10 years or more. 

The base Symetra runs 4x 120vdc 9ah packs (100-147v range), and can expand to 16 packs. They can output 37-75amps depending on the model, and can charge+service loads at up to 80amps input - advertised to charge a depleted pack in 3 hours. 

- Fair amp capacity
- Tower on wheels
- Dedicated genset input
- hot-swappable battery packs are already fused and cooled
- Its already in a fire proof casing
- It currently has good SLA batteries (unknown age)... would get swapped to LifePo soon and sold at the marina.
- 42S LifePo - I can wire that


Does this sound like a good choice of equipment to keep me online in an extended outage? I realize I probably will have to overcome integrating a BMS (42S??), and fool the grid tied inverters in to syncing off the UPS via transfer switches... and potentially burn off excess power to keep the load pulling from the solar... I could setup an arduino to monitor pack capacity and trip a relay to some hot water elements.

On another note, I already have 2 mid-sized Toshiba 1600EP UPS, 3.6kva, but they only do 15amps max output - not enough to safely handle the well.

Open to ideas/scrutiny. Sorry for TMI.
Disadvantages then?
Expensive batteries and need those specific ones.
Batteries not made to be cycled often
The device is not made for continues use
A UPS is not very power efficient

You cannot tie grid tie with the ups. Its not made for it and will overun the ups killing electronics.
Running Lithium on the ups not made for it is not really good unless you can set parameters. Yes discharge is ok but not charge.
BMS is always a must for lithium. LiFePo4 is better and would work but you need to be able to turn off bulk/float charge. Lifepo4 will be alot better without that. Even though they can be used...

I would say you should
1. Ditch your grid-tie gear since your real aim is for offgrid right?
2. Get a proper hybrid inverter if you want to sell excess and are approved. If not go for off-grid system
3. Use LifePo4 if you now have that. They are awesome.

A large ups can easily pull 200-500+w just idling.....
Take a look at my setup. Thats basically what you need to survive those outages.
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
Thanks Daromer, I figured you would have that answer... was a quick and dirty thought Wink
Free options are always worth something.... The scrap value alone may be greater than the costs... OR... some of the internal parts may be worth the value. I had looked at many UPS systems upto 24kVA (cheap eBay offers).

Building a powerwall for a high DC voltage input the UPS needs I would (and have) stayed away from after serious though and this is from an electrician who spent 11 years wiring stuff. I have felt, seen and caused enough flashes with AC, which would have been quite different with DC and more than likely would not be here....

DC faults from battery packs with very low IR are severe enough at low voltage and only end when the arc can no longer bridge the fault gap..

"A large ups can easily pull 200-500+w just idling....." - given you have 10kW of solar the loss of 5-7kWh per day may be quite significant in some seasons and a show stopper. Daily energy management / balancing is also a consideration.

With your skills and if you have time, building your own inverter setup may give you a better option. My 6kW inverter has idle around 25W and copes with all sorts of surges, cost a fraction the price and can be easily repaierd/replaced.

I went the build route after spending many hours researching existing inverters because I wanted my setup to be portable as I take parts of it to a remote location to run a remote mini grid power setup. When your miles away from anything reliability and maintainability take on thier own role/value.

Not for everyone and there are lots of issues but it can provide a very flexible base to develop on. Just a thought.

Technical spec of the SYA8K - efficiency 25% load approx 85%..... ouch...
120V DC battery (x2)
300W battery charger.... hmmm...

Show stopper : with the 8KVA unit that it aggregate and the per phase loading maximum is only 3.2kW.

Idle for the 8KVA does not seem to be quoted but from the efficiency charts it would indicate about 260W or... around 6kWh per day

Actually, all that said, if the existing cells still have life the unit may be ok as a standby unit for running power tools..
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
I have always had a fascination with enterprise equipment... and I've picked up my fair share of used stuff over the years as well. It's a lot of fun if you have a general curiosity about enterprise gear and want to learn. Especially for free, it can be worth it depending on what you want to accomplish.

The biggest hassle for me came from a time and storage... Unless you have to means to store and work on something so large, it can become a hassle.

For learning, hobby, fun sure... but for a production powerwall system I think there better things to consider.
I like the enterprise to. So if you need stuff that are heavy duty go for it. Like breakers, switches. Or just even copper to sell to the scrap Big Grin
Jim Jr. likes this post
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
In this case a 350kg enterprise boat anchor? ... it actually is very valuable to resell used, but transporting it is very expensive, the risks of moving heavy equipment make its value lower to me (what it fell on someones foot - broke the shiny toy and someone goes to the doctor)... If given more time to coordinate it properly and get all the right stuff to haul and unload it, a nice little concrete pad outside my garage, etc - I would have taken home the shiny toy and burned excessive watts just to have standby power on hand until I get the proper hyrbid inverter.
Yes these things are valuable, but the market for it is pretty limited, and the larger and more complex the equipment is, the hard it becomes to sell.

The thing about used enterprise equipment market is that most businesses won't buy them for use in a production environment. Most all enterprises wont deploy equipment without a SLA, warranty, or a service contract. UPS equipment also has a 3-5 year production life cycle.

This is precisely why we find really nice stuff like this at technology liquidators. Once bought a used $75,000 worth of HP server and SCSI SAN storage for $1500. I used it at home for a VMWare virtualization lab. Long story short, was a lot of fun to play with and learn, but when you compare it to modern tech, it's so power hungry that a business can justify ditching perfectly good gear on power consumption alone.

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