Black & Decker Handisaw I left it on the charger to long and now the battrey it dead

SOURCE: Black and Decker Battery Charger

Fault Codes Meaning of Fault Code F01 Internal Shorted Cell Battery - Cannot be charged. Have battery checked by certified auto service center.
Excessive Load on Battery While Charging - Check load. F02 Bad Battery Connection - Check battery connection.
Battery Voltage Tool Low to Accept Charge - Have battery checked by certified auto service repair. F03 Internal Open Cell - Have battery checked by certified auto service center.
Sulfated Condition - Battery needs to be reconditioned. See manual. F04 Overtime Condition - Battery will not accept a charge after 18 hours of continous charging. Battery may have internal
damage. Have battery checked by certified auto center.

Battery Charge Rate is Set Too Low - Set charger to higher charge rate. See manual. F05 Overheated Condition - Disconnect charger and allow to cool for 30 minutes. Check for ample ventilation. F06 Reverse Polarity F07 Alternator Output is Out of Typical Operation Range

Operation Codes I=I=I=I Battery Reconditioning - (The letters DES will display for the first three seconds) I-I-I-I Alternator Voltage Check OOO Charger Standby FUL Battery Fully Charged

SOURCE: black and decker cd12c cordless drill Charger

I would guess 12 volts

SOURCE: Black & Decker LITHIUM CHARGER 14.4v to 18v . 90539541. fits A1518L, HP1884L

could be either one. Have you tried another battery? If not I would recommend taking BOTH in for inspection. They have a scanner that can detect if the battery has a problem. If you need to find a service center close to you go to dewaltservicenet.com and they have a locator. Let me know if you need more assistance.