Black & Decker® BM3B - Battery Maintainer / Trickle Charger

55 reviews / Item # mpn2471521
Black & Decker® - Battery Maintainer / Trickle Charger
Black & Decker® - Battery Maintainer / Trickle ChargerBlack & Decker® - Battery Maintainer / Trickle Charger in UseBlack & Decker® - Battery Maintainer / Trickle Charger Installation InstructionsBlack & Decker Authorized Dealer
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 Black & Decker Accessories

Battery Maintainer / Trickle Charger by Black & Decker®. Keep your vehicle, boat, RV or other battery at peak charge with this battery maintainer. It’s great for 6V and 12V batteries, small or large. Prevent battery damage caused by self-discharge, and keep your batteries working at full capacity for many seasons.

Black & Decker - F.A.QBlack & Decker - About


  • 6V or 12V, switch controlled
  • Use for battery maintenance, charging RVs, specialty vehicles, antique and classic cars, marine deep cycle batteries, motorcycles, lawn mowers, tractors, ATVs, snowmobiles, personal watercraft and more
  • Maintains battery charge in stored vehicles
  • Charging indicators:
  • Red – bad connection, battery not able to accept charge, reverse polarity hook-up
  • Blinking Green – connection correct and charging
  • Solid Green – fully charged
  • ETL-Listed for safety
  • Fully automatic; powers on when needed, powers off when battery is fully-charged or topped-off
  • Built-in circuit protection guards against overcharging or short circuit
  • Automatically checks for correct polarity (requires a minimum of 2.0 volts battery voltage)
  • Convenient, color-coded ring terminals, clamps and power socket plug


  • Amperage (amps): 1
  • Assembled Depth (in.): 5.06 in
  • Assembled Height (in.): 9.62 in
  • Assembled Width (in.): 2.81 in
  • Automatic shutoff: Yes
  • Automatic/Manual: Automatic
  • Battery Test Function: No
  • Battery tester included: No
  • Certifications and Listings: 1-UL Listed,ETL Listed
  • Charger type: AC or DC
  • Cooling fan: Yes
  • Cord Length (ft.): 4
  • Engine start function: No
  • Handheld/wheels: Hand
  • Manufacturer Warranty: 1
  • Product Depth (in.): 5.06
  • Product Height (in.): 9.62
  • Product Weight (lb.): 1.35 lb
  • Product Width (in.): 2.81
  • Rechargeable: No
  • Reverse Polarity Protection: Yes
  • Voltage Output (volts): 120 V"

Letting an unused battery self-discharge itself will damage it permanently in only a few months. Keep any battery not in service charged, without overcharging it with this charger. It will charge a battery to 100% state-of-charge, and then patiently wait, monitoring voltage periodically. When the battery’s self-discharge (Usually 10%-25% per month of storage, depending on the temperature) draws down the voltage enough, a brief charge cycle brings it back up to peak charge. This is calculated to keep the battery ready for use, but more importantly, will fight sulfation caused by undercharge. This handy charger will charge a battery from the front seat if the power socket remains hot when the key is off. If not, you can still use the clip-on leads. Also included are a set of ring terminals you can install to the battery posts permanently, leaving you with a convenient SAE connector to connect and disconnect the charger.

Black & Decker is the 300-lb. gorilla of portable power tools, and since they patented the hand-held portable pistol-grip electric drill in 1916, it’s no wonder. They’ve also pioneered the cordless tool revolution, while maintaining industry leadership in the corded tool market. While Black & Decker tools are manufactured in 11 countries, they are marketed in more than 100.

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Product Reviews


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Black & Decker® - Battery Maintainer / Trickle Charger
Black & Decker® BM3B - Battery Maintainer / Trickle Charger
Average Rating: 5 of 5
5 of 5
Great Product, Great Price.
Black & Decker® - Battery Maintainer / Trickle Charger
Product is great. Extremely fast and easy to set up, and has been working great so far. Also very pleased by the low price. Would definitely recommend.
JPosted by (Nunica, MI) /
Was this review helpful for you? Yes
5 of 5
Battery Trickle Charge I Have Yet To Use
Black & Decker® - Battery Maintainer / Trickle Charger
Battery trickle I have yet to use this charger, but have read some good reviews I am looking forward to using it, when I head north to mass in April.
JPosted by (Quincy, MA) /
Was this review helpful for you? Yes
5 of 5
Black & Decker® - Battery Maintainer / Trickle Charger
Black & Decker® - Battery Maintainer / Trickle Charger
Works as advertised.
GPosted by (Saint Cloud, MN) /
Was this review helpful for you? Yes
5 of 5
Keep em Charged
Black & Decker® - Battery Maintainer / Trickle Charger
My Black & Decker battery chargers arrived on time and I was surprised how light they weighed. I hooked each charger onto my 1934 Ford coupe and my 1929 Ford 2-door Sedan. The hook-up was easy and the chargers work without ant problem. Anyone that has had a problem with one of these units needs to read the instructions first. I've never had a problem with a Black & Decker product.
KPosted by (Hemet, CA) /
Was this review helpful for you? Yes
5 of 5
Very Easy To Use
Black & Decker® - Battery Maintainer / Trickle Charger
I have a truck with many accessories, and I need the best battery to maintain the starting power. The reason I got the battery maintainer is that it keeps the battery at its top voltage all the time. I got the cigarette adapter for ease of not having to open the hood every time I connect the maintainer. I simply open the driver's side window a little bit and connect to the cig lighter receptacle. It works Great, & I'm very happy with it! For the price, It can't be beat!!!
CPosted by (Redmond, WA) /
2007 Ford F-150
Was this review helpful for you? Yes2   people found this review helpful.
Black & Decker® - Battery Maintainer / Trickle ChargerBlack & Decker® BM3B - Battery Maintainer /...    $17.08
55 reviews
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