BLACK+DECKER 6V/12V Battery Charger & Maintainer BM3B — 1.5A Compact Automatic with Clamps and O‑Ring Terminals

Designed for seasonal vehicles and occasional use, the BM3B helps keep 6-volt and 12-volt batteries at ready capacity without constant supervision. It’s compact, ETL-certified for safety, and includes both detachable cable clamps and O-ring (ring) terminals so you can hook it up directly or leave a permanent connection. The unit’s voltage selector and automatic float maintenance simplify charging for RVs, motorcycles, marine batteries, lawn equipment, classic cars, ATVs and other stored vehicles.

How do I connect and start charging safely?

Choose the correct voltage using the slide selector (6V or 12V) before connecting. Attach the charger using the included cable clamps for temporary charging or the O-ring terminals for a semi-permanent setup; the charger’s built-in protections reduce user risk. Power on, and the BM3B will manage the charge cycle automatically.

• Select 6V or 12V with the voltage switch before making connections.
• Use clamps for quick hook-up or ring terminals for long-term installation.
• Unit offers reverse-polarity, short-circuit and overcharge protection.

What battery types and vehicle uses are supported?

The BM3B is compatible with common lead-acid battery chemistries used in small engines and stored vehicles: AGM, GEL and wet (flooded) batteries. It’s sized and tuned for auxiliary and starter batteries on motorcycles, lawn tractors, ATVs, snowmobiles, personal watercraft, classic cars, marine deep-cycle applications and RVs.

• Charges and maintains 6V and 12V AGM, GEL and wet batteries.
• Suitable for small engine starter and many deep-cycle battery types.
• Ideal for seasonal storage applications where batteries sit idle for weeks or months.

How does the automatic maintenance function work?

Once the battery reaches full charge, the BM3B stops active charging and shifts to a float/monitor mode that keeps voltage topped off without overcharging. This automatic transition eliminates the need to disconnect the charger and prevents battery stress from prolonged high-current charging. The charger continually monitors battery condition while in float mode.

• Stops active charging at full capacity and enters float monitoring.
• Prevents continuous overcharge by automatically regulating output.
• Maintains battery readiness during long storage periods with minimal supervision.

What safety and installation features should I know about?

The BM3B includes built-in circuit protections and is ETL certified to meet safety performance standards. A built-in mounting bracket simplifies installation inside garages, on walls or frames so the unit can be positioned close to the battery. The charger’s compact footprint and universal fit make it convenient for many setups.

• ETL certification for tested safety and performance standards.
• Protection from reverse polarity, overcharging and short circuits.
• Integrated mounting bracket for secure, out-of-the-way placement.

Who is this for? The BLACK+DECKER BM3B is intended for vehicle owners, hobbyists and seasonal users who need a low-maintenance way to preserve battery health when equipment is idle. If you store an RV, motorcycle, mower, classic car or watercraft for weeks or months at a time and want a compact, safe charger that automatically finishes charging and then monitors battery voltage, this model provides a simple, cost-effective solution backed by a one-year limited warranty.