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1.2 Amp Portable Car Battery Charger/Maintainer Compatible with 6 and 12-Volt AGM, GEL and WET Auto/Marine Batteries

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  • Compact 1.2 Amp Maintainer ideal for topping off charge
  • Compatible with AGM/GEL/WET 12V battery systems
  • Integrated safety features including reverse polarity protection
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Product Details

About This Product

The Black + Decker Battery Maintainer/Charger is designed to keep your 6 Volt and 12 Volt batteries at optimal capacity year-round. It's perfect for vehicles that only see seasonal use, including RVs, specialty vehicles, antique & classic cars, marine deep cycle batteries, motorcycles, ATVs, snowmobiles, personal watercraft and more. Keep it plugged in during the off-season, ensuring your batteries will stay topped off without ever being overcharged or damaged. It comes with two different connector sets, including battery clips and battery terminal rings.


  • 1.2 Amp Battery Charger/Maintainer compatible with 6- and 12-Volt AGM, GEL and WET automotive/marine batteries
  • 2 easy ways to connect (battery clips, or o-rings) for maximum convenience
  • Compact, impact-resistant polymer housing with integrated mounting bracket for easy mounting and storage
  • High-frequency charging that automatically switches between charging mode and float mode monitoring
  • Low-voltage compensation ensures maximum performance when used with extension cords
  • Click here for more information on Electronic Recycling Programs
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Product Information

Internet # 202710992

Model # BM3B


Dimensions: H 9.62 in, W 2.81 in, D 5.06 in


Product Depth (in.)

5.06 in

Product Height (in.)

9.62 in

Product Width (in.)

2.81 in


Amperage (A)

1.2 A



Charger type

AC or DC

Cord Length (ft.)



No Additional Features



Product Weight (lb.)

1.35 lb



Voltage Output (volts)

120 V

Warranty / Certifications

Certifications and Listings

ETL Listed, UL Listed

Manufacturer Warranty


Questions & Answers

Q:can the bm3b be used to charge and recharge lithium polymer batteries?
by|Jun 21, 2021
2 Answers
Answer This Question

A:  It should, this charger usually acts as a trickle charge. It works great on car and motorcycle batteries

by|Jun 22, 2021

A:  Mine won't charge anything. It had a fracture in a solder joint on the circuit board. Additionally, when I received mine, the polarity colors on the battery pigtail were reversed, and I had to correct that.

by|Sep 16, 2021
    Q:Can I use this to maintain the battery charge for a portable generator that I use when there is a blackout...n electricity in my house?
    by|Dec 2, 2019
    2 Answers
    Answer This Question

    A:  Yes, It's a battery maintainer. Works very well .

    by|Dec 4, 2019

      A:  Yes, Just as long as this battery is 12Volt.

      by|Dec 3, 2019
        Q:Can this be used on Lithium Iron Phosphate (LiFePo) batteries? Same question for Lithium Ion batteries.
        by|Jul 18, 2019
        3 Answers
        Answer This Question

        A:  No, lead acid batteries only.

        by|Jul 20, 2019

          A:  This battery maintainer is designed for 6/12V lead acid batteries. It was not designed for Lithium Batteries.

          by|Jul 19, 2019

            A:  I would not use thus charger for those batteries

            by|Jun 22, 2021
            Q:Does this recondition batteries while charging? (by reversing sulphate buildup)
            by|May 28, 2019
            3 Answers
            Answer This Question

            A:  No, This unit does not have recondition function. Try our line of large battery chargers that have this feature.

            by|May 28, 2019

              A:  The information that came with the re-charger does not say anything about this build-up. An alternative solution is using lithium-ion, a battery that prefers a partial charge to a full charge. However, Li-ion is more than double the cost of lead acid. Although more expensive, the cycle count is said to be cheaper than that of lead acid because of the extended service life. To be honest, I never gave it a thought.

              by|May 28, 2019

                A:  I don't think it does

                by|May 28, 2019
                Showing 1-4 of 26

                Customer Reviews

                4.2 out of 5

                • 4.2 out of 246 reviews
                • 79% recommend this product
                Filter by:
                Showing 1-10 of 246 reviews
                Works like a champ
                Use this on my stored convertible and it has been working great for 4 years.
                  • Recommended
                  I have had other brand trickle chargers that are more expensive and have failed. I have two of th...
                  I have had other brand trickle chargers that are more expensive and have failed. I have two of these and one larger maintainer, they work great. Always ready to run. I have used the permanent leads on each car, but there is also a set of battery clips and a cigarette lighter adapter that can be used as well. There is also a warning indicator to keep it from being connected wrong.
                  • Verified Purchase
                  • Recommended
                  1 found this review helpful
                  Cost effective maintainer
                  Bought one of these last winter when my daily driver started cranking kind of slowly. Unfortunately I don’t take long drives and so the car alternator never had a chance to charge the battery fully. I’ve been using this trickle charger for a year now and it seems to be doing the trick. Now my battery is at five years and my wife’s is at six. Hoping we can get through one more winter with judicious use of this charger.
                    • Recommended
                    My Jeep likes to drain the battery and she doesn't get driven often so needed something to keep t...
                    My Jeep likes to drain the battery and she doesn't get driven often so needed something to keep the battery charged between trips. Works great!
                    • Verified Purchase
                    • Recommended
                    4 found this review helpful
                    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!!
                    • Recommended
                    16 found this review helpful
                    Worked for 6 years, then died on me
                    Not a terrible charger. used for a motorcycle for a while. now will blink green for a minute and then switch to the solid red "swap terminals" light. Terminals are connected to the correct polarity. tried on other batteries, same result.
                    Response from BLACK+DECKER® SupportAug 4, 2022
                    We appreciate your feedback on the BM3B and are sorry to hear about the issue you are having with your product. Please email us at wecare@sbdinc.com and reference ticket # 5093842. We look forward to hearing from you.
                      • Recommended
                      Died in less than 2 years
                      Just died in only 18 months. Always in the garage, keeping a brand new red top battery full. Hadnt checked on it in a few weeks, and now battery is dead, no lights or charge on this thing.
                      Response from BLACK+DECKER® Support Aug 12, 2022
                      We appreciate your feedback on the BM3B and are sorry to hear about the issue you are having with your product. Please email us at wecare@sbdinc.com and reference ticket #5185546. We look forward to hearing from you.
                        Dangerous and costly
                        This piece of junk destroyed my battery. Nothing like the products of the past.
                        Response from Social MediaFeb 22, 2023
                        Hello. I appreciate your feedback on the Charger and I'm sorry to hear about the issue. Your satisfaction is our top priority. Please contact support at WECARE@sbdinc.com and reference ticket (#6568133) so we have all information available from your review. I look forward to hearing from you so we may assist you with a solution. Thanks, Maria BLACK+DECKER Social Media Team
                          Works fine on aircraft battery
                          Works as advertised. No problems. Nice long power cord to reach the outlet without extension cord.
                            • Recommended
                            Work great for me for years!
                            I bought one to keep hooked to my parked vehicle while I rotate driving my vehicles every few months. I have not had dead battery issues since. They crank my starter rather aggressively every time. I also bought one for my ATV after another brand quit working. I’m not sure what is happening to other reviewers. (The ones who rate anything other than the product don’t count.)
                              • Recommended
                              Showing 1-10 of 246 reviews