I am assuming that your charger is the old school "hook it up and give it hell" style. Other than the transformer, ammeter, circuit breaker, and rectifier, there really isn't much to go wrong with one. I just rebuilt an old non-boost charger with a new rectifier and ammeter for under $30.

Why, because I hate these new "smart" chargers. Battery voltage too low, won't work. Decides when the battery is fully charged and most of the time it's not. Want a power supply to test motors like wiper and blower, won't with these.

No, sometimes technology is not our friend.