Model # BM3B

Internet # 202710992

Store SKU # 273222

120-Volt Battery Maintainer

$20.48 /each

Frequently Bought Together

Product Overview

The BLACK and DECKER BM3B is ideal for keeping your 6-Volt or 12-Volt battery fully charged when not in use. Simply plug the maintainer into any AC outlet and connect to your battery in any one three ways: Battery clips 12-Volt Dc accessory plug or the battery terminal rings. The BM3B will do the rest of the work, monitoring your battery with the Automatic micro processor, so that you can never over charge the battery.

  • For use with both 6-volt and 12-volt batteries
  • Automatic microprocessor battery monitoring
  • Reverse connection warning and ready indicator
  • 3 ways to connect battery clips, 12-volt accessory plug, and battery ring terminals

Info & Guides

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Product Depth (in.) 
Product Height (in.) 
Product Width (in.) 


Amperage (amps) 
Automatic shutoff 
Battery Test Function 
Battery tester included 
Charger type 
AC or DC 
Cooling fan 
Cord Length (ft.) 
Engine start function 
Product Weight (lb.) 
1.35 lb 
Reverse Polarity Protection 
Voltage Output (volts) 
120 V 

Warranty / Certifications

Certifications and Listings 
1-UL Listed,ETL Listed 
Manufacturer Warranty 

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Customer Questions & Answers

1 Question2 Answers

Customer Questions & Answers

120-Volt Battery Maintainer
120-Volt Battery Maintainer

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This question is from 120-Volt Battery Maintainer
2 answers

May I leave this BM3BC model charger connected and charging for an extended period eg: 6 months?

This question is from 120-Volt Battery Maintainer
Asked by
Calgary AB Canada
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October 2, 2015
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Answers (2)

Asked by
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January 13, 2016
Yes, that is how this charger is supposed to work, it's a "maintainer". However in my experience, the charger will not kick in when it should and will let the battery go dead. I would not recommend this product.
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Asked by
Flagstaff, AZ
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Home Improvement Profile: Professional
October 3, 2015
YES, Mine sits on my ATV months at a time.
2out of 2found this answer helpful.
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Customer Reviews

Rated 4.8 out of 5 by 42 reviewers.
Rated 5.0 out of 5.0 by Great product This is my second charger and they both work great, I like the multiple attachments, I have one on my GoldWing motorcycle and the other on the motor home. February 17, 2016
Rated 1.0 out of 5.0 by Finally threw mine in the trash - battery went dead too many times After finding my battery dead too many times while this charger was connected, I finally threw it in the trash. I tested the voltage at the battery, 11.6 which is obviously low. This charger would charge for a few seconds and then switch into float mode, no longer charging. I should have spent more money on a better product. I don't think it was a bad unit, I have two of these and they have both let me down. January 13, 2016
Rated 5.0 out of 5.0 by Terrific unit I found myself in a situation where I had to store my motorcycles remotely, while I moved cities. At home I used a an ultimate unite that I swapped between 3 bikes, but with a move I had to store the bikes a 2 hr drive away for several months and I had to find an alternative, reasonable cost solution. The ultimate is a great device also but way more costly. I decided to order two of these B&D units as I have always been happy with their products. I researched the background and figured if B&D bought the company that designed these they must be OK. I hooked up two of my bikes with these units and left them for 5 months alone in storage hoping I would not need to buy new batteries when I got the bikes out. When I got back, the green LEDs were illuminated on both units. Turned the keys and both bikes started up like champs. Batteries were strong cranking and kept fully charged. I have since moved the bikes to the new house and these units are on them constantly while we endure winter in the east. really really satisfied with this product. At 20 bucks each I already exceeded the value from them in saving me over $200 cost in new bike batteries. They saved me in this storage and now are holding me through winter. Enough said!! December 6, 2013
Rated 5.0 out of 5.0 by DOES THE TRICK, OR SHOULD I SAY TRICKLE...... Have a car that is sitting in garage now and the battery is slowing being tapped , so I hooked this up and in about 24 hrs. , brought it right back to snuff...I followed the next week and it only took about 4 hrs. to top it,,,,,,.I do agree with others the volt. selector switch is too easily moved from 6-12 volts....but just be careful or tape over it....It's better to slow charge a battery than rapid with higher amps in the long run.....and this is about 1.2 amps..vs.. 4-10 amp units.... December 30, 2014
Rated 5.0 out of 5.0 by Piece of mind having my battery maintainer Bought the 6/12 volt battery maintainer so I would not have to worry if there was enough charge on my battery to start my "classic" car. My car sits in a separate garage and I don't start it every week, sometimes not for a few weeks and at times the car has a hard time starting and I have to hook up the charger or jump it. Now with the battery maintainer, I never have to worry if there is enough juice to start my 1937 Dodge!!!! I wish I would have done it years ago. December 10, 2014
Rated 4.0 out of 5.0 by Battery Trickel Charger I use this charger on my lawn tractor to keep the battery fully charged, especially in the winter. It works well for me, as it is small, portable and has long enough leads to fit from under my carport to the tractor. Best of all, the price is very affordable and it is very easy to use. Mr. T El Paso, TX January 20, 2015
Rated 5.0 out of 5.0 by excellent features for the price every one knows that the extreme cold is very hard on batteries. i've always had problems with my 4 wheelers and tractor batteries going dead over the cold winter months. not this year. keeps them fully charged and ready to start for when snow falls. and we got a lot of snow this year. i never had to jump start a unit. i like that it had 3 different ways for connections. you could actually rotate the unit weekly to charge different pieces of equipment. it was pretty inexpensive so i just bought 3 of them. its a lot cheaper than a $65 ATV battery. February 8, 2014
Rated 5.0 out of 5.0 by Best price for the best battery maintainer This is the best battery maintainer on the market. A good friend of mine recommended it as it is all electronic and does not require a transformer. Also Home Depot had the best price and I picked it up at my local Home Depot. January 3, 2015
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