Re: (ET) Ok, just ordered the 20uf capacitor for my E15

[David Tiefenbrunn <davidtief comcast net>]

You can use motor run capacitors.  They are rated for continuous use.

Use the same uF = mF as the original, same or higher voltage.

Motor start capacitors will fail in continuous use, like a charger. They 
are only made to handle a short surge while a motor spins up.

The capacitor and the winding and air gap in the transformer make a 
resonant circuit that limits current and / or regulates voltage. The 
diodes make the AC to DC to charge the battery.