BLACK+DECKER BM3B Battery Charger and Maintainer
- 6V and 12V AGM, GEL and WET batteries
- 1.5 A charge rate
- Auto float mode when full
- Battery clips and O-ring terminals included
- ETL certified, reverse polarity protection
- Built-in mounting bracket
- Limited One Year warranty
Last refreshed Sep 7, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A small automatic maintainer for keeping stored cars, motorcycles and mowers ready through the off season. Its low current makes it a maintainer, not a fast charger for dead batteries.
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ASIN: B0051D3MP6Model: BM3BCategory: Car Battery Chargers
Overview
Connecting this BLACK+DECKER maintainer to a stored vehicle holds its battery topped up all winter. Slide the switch to six or twelve volts, attach the clips or ring terminals, and it charges, then drops to float mode to watch the battery.
Owners of seasonal vehicles get a set and forget unit with ring terminals for permanent hookup and a bracket to mount it. The low current is too slow to quickly revive a fully drained car battery.
Who it's for
Riders and collectors who park vehicles for months will use the float mode and ring terminals. Drivers who need a fast charge before work should get a higher amp charger.
Pros and cons
- Handles both six and twelve volt
- Works with AGM, GEL and WET
- Ring terminals for permanent hookup
- Automatic float mode
- Slow charge rate
- No lithium battery support
- No display of charge level
Performance notes
Charge speed is set by the low current output, which suits topping up rather than recovering a flat battery. Float mode monitors voltage and adds charge only when it drops, which avoids overcharging in long storage. Protection circuits stop it from charging if clips are reversed or shorted.
Specifications
| Brand | Black+Decker |
|---|---|
| Model | BM3B |
| Dimensions & fit | |
| Item weight | 1.2 pounds |
| Item Dimensions D x W x H | 5"D x 1.6"W x 2.6"H |
| Power & efficiency | |
| Amperage | 1.5 A |
| Voltage | 6V or 12V selectable |
| Compatibility & installation | |
| Compatible Devices | Vehicles and equipment that use 6V or 12V AGM, GEL, or WET batteries |
| Warranty & support | |
| Warranty Description | Limited One Year |
| Other details | |
| Number of Ports | 1 |
| Connector Type Used on Cable | Battery Clips, O-Ring Terminals |
| Specification Met | ETL |
| Eu spare part availability duration | 10 years |
Frequently asked questions
Does it switch off when the battery is full?
It stops charging when the battery is fully charged and switches to float mode monitoring.
How do I connect it?
Use the included battery clips or the O-ring terminals, and set the selector to 6V or 12V.
Can I mount it?
Yes. A mounting bracket is built in.