My shop must stay open as long as there is inventory. The business is utterly dependent on a functioning computer. Commercial battery backup systems I've seen simply aren't designed for an extended blackout.

Have an appropriate Tripp Lite inverter, a bank of 3 deep cycle Delco Voyagers, a plug outlet fed charger and a Briggs/alternator rig for topping off after a blackout.

What I can't find are answers to;

1) How long can I reasonably expect this setup to provide adequate power for puter, screen & one printer before needing topped off? Can't run alternator rig continously and shouldn't need to.

2) Will less than 110V hurt the puter and if so is there a device to shut it down automatically beforehand? Would a voltmeter on the batts solve and if so what's the danger point to watch for?

Have asked a couple of computer shops plus my local ISP guy but they all think in terms of off the shelf, short-time back systems.

Thanks now for any advice or referrals.

-- Carlos (riffraff1@cybertime.net), October 19, 1999

Answers

How much power (watts) does your computer setup use? What size are the batteries -- Amp-hour rating, not starting amps (they're the wrong kind -- get some golf cart batteries).

-- Dean -- from (almost) Duh Moines (dtmiller@midiowa.net), October 19, 1999.

Have you considered using a power conditioner plugged into the inverter?? Just to make sure etc?? I seem to remember that some of them had meters on them to show the status of the power input. Pluys, they are self topping while the power is GOOD.

Chuck

-- Chuck, a night driver (rienzoo@en.com), October 20, 1999.

read the directions for you inverter if you have them.

It should shut down when the batteries reach a certain level of discharge.

the computer *should* be able to operate at voltages from 90 to 130.

How long your system can provide power will depend on how often you run the system. When you are not using it, dim the monitor, in fact, keep it dimmed as low as possible while using it.

-- plonk! (realaddress@hotmail.com), October 20, 1999.

If you can afford it, get one of the new LCD flatscreens. That will save a LOT of power.

MFU

-- Man From Uncle 1999 (mfu1999@hotmail.com), October 22, 1999.

Carlos...You will need to supply more info to get a real answer. If the printer is a laser it will suck up major power and the Tripplite inverter you have will likely fry it anyway. Personally I wouldn't use a Tripplite product....the UPS and inverters made by them we tested were really horrid (really poor waveform, varying frequency, low peak voltages, unreliable, etc.).

The PC I'm sitting here using is drawing about 200 watts with the Epson inkjet printing (Powermac w/ 17" monitor). I'll guesstimate your batts at 100ah capacity and the inverter at 80% efficency. You should know that you REALLY don't want to drag these warmed over car batteries below a 50%^ state of charge (you should have gotten real deep cycle batts such as golf cart batts). Anyway a 100ah battery will basically produce about 1200 watt-hours of power, enough to run my computer system about 3 hours if I only drain the batts 50%. Since you have three batts that means 9 hours less the inverter inefficency (at 80% efficient This means your system could run 7.5 hours approx).

There are many factors that determine how much power you'll get from the batts including discharge rate, cell temperature and battery age (level of inherent sulfation). We could write a book on this (well, a magazine at least...which we have for 13 years) but this gives you at least an educated guess.

DCK Home Power Magazine, http://www.homepower.com

-- Don Kulha (dkulha@vom.com), October 24, 1999.