Since adding the 85ah deep cycle battery to the old conext900 has gone well, I’ve decided to move forward with the project and install and modify a larger UPS.
I searched ebay and lost my first few auctions, finally I have won a dell DLA3000RM2U, which is reportedly new in the box, and so it may have usable batteries with it — though if it has been new in that box for 3 years, probably not. In retrospect I probably should have kept searching, as this UPS does not have an external battery connector, and I still do not know if it is 24 or 48 (or other) volts internally. Most UPSes which have external battery connectors are build to withstand long run times, and most use 48VDC. It’s possible that this system will not be happy running for hours with a large load, I will need to monitor the temperature of its components closely. If it proves difficult to use, I suppose it will go back on ebay or craigslist, though at $95 s&h, I’d rather it not. a3KV unit is also the largest 110V UPS you are likely to find, while I could easily have ran 220 to the computer area, it seemed like overkill.
I also purchased an APC network card, expansion box, and environmental controller+probe. My total ebay purchases are now: 102+11 for the cards and probe, and 104+96 for the ups, or $313 in all. Though the unit is 110V, it does require a high-amperage plug. I picked up some 10/2 romex, the receptacle, a box, etc, and tagged it off one leg of a 30amp circuit running to the dryer. I will also need to monitor this circuts load and wire temps when the dryer is running and the UPS is under load. It’s possible that I will need to tag in a new breaker and run a new line. The wire was $23, the receptacle about $10 and another $10 for the box/plate, etc. so we are up to $346.
In anticipation I picked up 2 deep cycle batteries from SAM’s Club. They are Energizer 29HM units, there was not much documentation on them, but based on what I could find on the net, plus their weight relative to the 27DC being sold next to it (which had slightly more info online), I _think_ they are true deep cycle units, vs hybrids or marine starting batteries. These _should_ be 125ah batterie with a 210RC, we’ll see when they are in use. They were $90+core&tax, around $114 each. I put them in a large plastic tub and put about 3lbs of baking soda below them (also from Sam’s club). I have about 10′ each of red and black 8g wire, and 10 crimp connectors and a bus-bar ($20). That’s another $248, bringing the total for this project to nearly $600. If it turns out to be a 48V internal unit then I will need 2 more batteries, more cable, etc. and I’ll be looking at $850. Which is quite a lot for a home ups (plus the $105 I already have in the conext, though it will be repurposed to power my point-to-point wireless and wiMax links). However, that should run all of my servers and associated gear for several hours during a blackout, and if cared for, should last 5-8 years (or longer at reduced capacity). So depending on the final costs that’s $5-11/month for power protection. Sounds a lot better that way anyway. If I’m lucky the unit will be 24V and the $600 figure will be the total, I’ll get 8 years of it as-is, and it’ll be $6.25/month. Given that I’ve been replacing 1-3 UPSes a year at $60-$175 each, it should be the same or less cost, and after the initial struggle, less hassle — but mostly waaay more actual protection. Also note that the $114 for the monitoring hardware was not strictly needed.