Stephen Gregory nslug at kernelpanic.ca
Sun Dec 18 18:39:54 AST 2005

On Sun, Dec 18, 2005 at 05:33:36PM -0400, Donald Teed wrote:

> power that is dirtier than from the electrical company, then
> why do we have them?

Because switching power supplies don't care that much. Old cheap UPSs
would produce an almost square wave. New cheap UPSs produce a stepped
aproximation of a sine wave. Think of a hill with stairs going up one
side and down the other. That is what the waveform looks like. True
sinusoidal waves are hard to produce with electronics. The good
expensive UPSs produce good clean sinusoidal power but it is

> be a bad idea.  Given that lead acid batteries have a life
> span defined by the shedding of materials inside,
> you want to reduce the consumption of the compounds.

The lead acid cycle is almost 100% reversable. A lead acid battery
that is properly treated (not under charged, not over charged) will
survive many cycles. A deep discharge produces sulfation which
consumes the acid. Overchargeing causes the battery to boil away, and
IIRC some of the lead is turned into a non soluble form of lead.

Most UPSs overcharge the batteries. 

You need to test the AC under load because the electronics of the
inverter are designed to work with a load. Without a load the AC
voltage could be high or low. It depends on the design of the circuit.



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