Hi Brian,

If you have a digital multimeter, you can check the voltage of the battery. Should be about 12.6 volts. My Miata still started with 11.95, but it was not taking a charge over 12.04 even after having it on a tender all night. New battery came with 12.65 Volts. Once had a tender go out on me that was supposed to keep my motorcycle battery charged.

Good luck

Reinhard Kreutzer