MPI,

Get a MPI switch with charge jack and LED indicator lights. When the light on top is green your good to go. When the second yellow light starts to change to yellow when under load you might have one more safe flight. I never let it get to the bottom red light. I must aggree though a volt meter with this type switch is the way to go. At least with this switch you can check the battery without taking off the wing. Don't ever trust lights totally. Get the meter.

JMHO,

Gibbs