Walmart has BLACK+DECKER BM3B 6V and 12V Battery Charger/Maintainer (BM3B) on sale for $11.24.
- Circuit protection against overcharging or short circuit
- Fully automatic high-frequency charging
- Connects to the battery via clips
- 12V plug & battery ring terminals
- Reverse polarity protection
- Includes built-in mounting brackets & AC plug
- Works with 6V & 12V battery systems