Homestead mailing list

["Wendy" <crazygardens AT verizon.net>]

> At 6/1/2005, you wrote:
> > > I cannot see using solar as a stand-alone system. My planer has a five
> > > horsepower motor. Batteries would never handle the starting load.
> >
> > Do batteries start your car?
>
> Very different loads and batteries.  To start an AC load such as a
> synchronous motor, you have to contend with huge inrush currents before
> back EMF increases the load and reduces the current.  The high starting
> loads add to the power requirements.  Inverters are sometimes designed to
> handle those surge currents but they do drag the battery into low voltage.
> Sometimes the inverter will see this low voltage and shut down.
>
> Deep cycle and marine batteries are designed for steady current drain to
> get maximum capacity.  SLI (starting, lighting, ignition) batteries are
> designed to generate large amounts of current quickly then just as quickly
> recharge.  The starter motor is a fractional horse power motor so has
> smaller inrush currents, also as both field and stator coils are
> energized, back EMF builds much more quickly.
>
> Don Bowen                          Awl Knotted Up

You are absolutely right, Don.  It is not a good comparison.  What is
usually done with RE systems, is the AC motors are replaced with DC motors.
If you add a clutch and gear assembly that allows the motor to start
no-load, then the load is applied more gradually, would place even less
stress on the batteries.  I wouldn't want to use an inverter anywhere except
where it was absolutely necessary.  For the most part, they are an
unnecessary expense and a waste of power.

Wendy