What does it mean when the battery charger jumps from 0 to fully charged and then a couple minutes later jumps back down to 0 charge Does that mean the battery is no good?

When a battery charger jumps from 0 to fully charged and then quickly drops back down to 0, it typically indicates that the battery is unable to hold a charge. This behavior suggests that the battery may be faulty or degraded, often due to age or damage. It's advisable to test the battery with a multimeter or seek a replacement, as it likely can no longer be relied upon for proper performance.