Thanks Ted, that's really good info. It sounds like my old cheapie APC is not a good foundation for a better UPS.
Actually I'm more interested in handling extended outages than in instant failover. I use Reiserfs for just about everything here and it has been reliable so far in not trashing things when power fails. Maybe I'll just go for the inverter, a deep cycle battery and a moderately cheap charger, and keep them on hand but not actually running the computer all the time. BTW do you know anything about gasoline-powered generators? That may be a more comprehensive solution. Thanks again, -- Rod On Saturday 06 March 2004 10:53 pm, Ted Deppner wrote: > On Tue, Mar 02, 2004 at 03:13:07PM -0800, Rod Roark wrote: > > Thanks to everyone for the informative replies. Probably > > what I'll do is look for a smallish battery in an auto parts > > store to experiment with, and post here again when and if > > anything comes of it. > > Lots of good stuff already said, but figure I'll briefly chime in with > some of my experiences. > > Those sealed lead acid batteries in good UPSs have a life of 2 or 3 > years on the outside. They're not really good like a good marine > battery for deep cycling, but being a lead acid they can take some abuse > (very similar to a car battery). > > The issues with using a wildly higher current battery are fairly obvious. > A 7Ah batter versus a "650 cold cranking amp" battery than can easily > sustain 20+Amps for a good long time (10s of minutes). A 7Ah battery > would only look like a dead short to the charger for minutes... a dead > car battery could look like a dead short for an hour. > > Dangers... Only the cheap car cells still give off hydrogen (under > normal conditions anyway), you can get sealed car batteries. I've seen > 4 or 5 year old APC units burn up their circuit boards when new > batteries where put in. The low end units with < 10Ah batteries > typically have a charge controller that's on a PC board. Your typical > car charge controller is an ABS plastic thing (or older bakalite). Big > difference in current capacity, heat load, etc. > > If you can handle the possibility of fire and things exploding, have > some fun. The current is enough to burn you and cause fires, but you > can be safe about experimenting, and it's always fun. (You might be > able to isolate the inverter from the charge controller and then > integrate your own charge controller for instance.) In my estimation a > small UPS is good for one or maybe two battery change outs, ie a battery > change every 1 to 2 years, and the unit over all having a useful life of > 3 to 5 years. > > All that said, investing in a heavy duty DC power supply, a car battery, > and a DC-AC inverter would probably be a safer and ultimately less > expensive and more useful endevor. DC-AC inverter would be less than > $100, battery $50 on sale for a decent one. Not sure on the DC power > supply, it would need to be able to sustane 25 Amps continuously, as > you'd be actually running off the inverter the whole time and not be > "switched from AC to DC on power failure". > > A simple car battery charger won't do for this (I've tried)... most of > them have 'auto shut off' modes where they pulse on and off, while your > battery drains current but the voltage stays high enough to shut off the > charge sequence. You can run like this for several hours though in a > pinch. > > A good link for this is http://www.dansdata.com/diyups.htm which showed > up on Slash dot a few years ago I believe. > > -- > Ted Deppner > http://www.deppner.us/ _______________________________________________ vox-tech mailing list [EMAIL PROTECTED] http://lists.lugod.org/mailman/listinfo/vox-tech
