BLACK+DECKER 6V/12V Battery Charger & Maintainer — BM3B 1.5A Automatic Float for AGM, GEL & Wet Batteries

BLACK+DECKER BM3B is an automatic 6V/12V battery charger and maintainer that safely charges AGM, GEL and wet batteries and then holds them at proper voltage with an automatic float mode.

The BM3B from BLACK+DECKER is a compact, high-frequency charger designed to keep vehicle and leisure batteries ready during storage or long periods of low use. It supports both 6-volt and 12-volt systems and works with deep-cycle and starting batteries found in cars, motorcycles, ATVs, lawn tractors, boats and classic vehicles. With built-in protections and simple hookup options, it’s made for seasonal vehicle care and routine battery maintenance.

How do I connect and set the right voltage?

Select 6V or 12V using the slide selector on the unit, then attach either the included cable clamps or the O-ring (ring) terminals to the battery posts. Ensure correct polarity before connecting; the charger will protect against reverse hookup but correct connection is safest. Mounting the charger with the built-in bracket keeps it stable during charging.

• Slide selector chooses 6V or 12V charge mode
• Includes cable clamps for temporary hookup
• Includes O-ring terminals for permanent or semi-permanent installs
• Built-in bracket for secure mounting during charging

What battery types and vehicles will it work with?

The BM3B handles AGM, GEL and flooded (wet) lead-acid batteries and supports both starting and deep-cycle applications. It’s suitable for automotive, marine, powersports and lawn equipment batteries commonly found in RVs, classic cars, personal watercraft, snowmobiles and garden tractors. Use it to maintain batteries in stored vehicles or to top off batteries after short-term use.

• Works with 6V and 12V AGM, GEL, and wet lead-acid batteries
• Compatible with cars, RVs, boats, motorcycles, ATVs, and mowers
• Appropriate for deep-cycle and starting battery designs
• Good for seasonal storage and off-season maintenance

How does the BM3B prevent overcharging and protect the battery?

The charger features automatic stop-and-float behavior: when the battery reaches full charge it stops active charging and shifts to a float/maintenance mode to hold charge without overcharging. Built-in circuit safeguards guard against reverse polarity, short circuits and potential damage from improper hookup. The charger is ETL certified, indicating it meets recognized safety standards.

• Automatic stop when fully charged, then switches to float monitoring
• Circuit protection vs. reverse polarity and short circuit
• ETL certification for tested safety and performance
• 1.5 amp output suited for slow, battery-friendly charging

How fast will it charge and when should I use it?

At 1.5 amps, this unit provides a slow, controlled charge ideal for maintenance and topping off rather than fast recharging from a deep discharge. It’s best used for maintaining battery health during storage, keeping seasonal vehicles ready, or slowly recovering lightly discharged batteries. For deeply drained batteries, a higher-amp charger may restore charge faster, while the BM3B excels at safe, long-term upkeep.

• 1.5 amp output for steady, maintenance-friendly charging
• Designed for topping off and long-term float maintenance
• Not optimized for rapid recovery from heavily depleted batteries
• Ideal for off-season storage and regular battery upkeep

Who this is for: The BLACK+DECKER BM3B is aimed at vehicle and equipment owners who need a dependable, easy-to-use charger to preserve battery life during storage or infrequent use. It’s a good fit for owners of classic cars, RVs, boats, motorcycles, ATVs, lawn mowers and snowmobiles who prefer a compact, safety-certified charger with both clamps and ring-terminal connection options. If you want a low-maintenance way to keep lead-acid batteries healthy over weeks or months, the BM3B offers a practical, protective solution.