Battery Tender 4 AMP Battery Charger and Maintainer - Automotive Switchable 12V or 6V Smart Automatic for Cars SUVs and Trucks - Lead Acid, AGM, Gel, & Lithium Battery Charger - 022-0209-BT-WH

I have been using this battery tender on my boat for quite some time. My batteries always stay fully charged thanks to it. The tender maintains the batteries even through the cold winter. Come spring time i'm confident in taking my boat out onto the water again. Additionally I have never worried about overcharging the batteries because this tender has built in safeguards against it. It's been a solid purchase and I would recommend it for Boats, lawn equipment and anything else Having a 12 volt battery system.

This 4 AMP battery charger works great! It’s super easy to use. You really don’t need the instructions for the most part. It’s a very good value for the money.

I have 6 of these for my 6 cars which I use when I travel. They just work great. No more dead batteries when I return home

Perfect size for our use. Cold weather we need to make sure vehicles are good to go. Medium price for unit. Easy to use. Can read it without glasses

A really nice charger that can charge a wide variety of batteries. Four amps gets the job done quickly without risking battery damage, and the charger can be left in ‘float’ mode (which is automatically engaged once the battery is fully charged) indefinitely without fear of battery damage. There are more expensive chargers which are all dressed up to look more modern and sophisticated, but to my mind they offer nothing more than this charger. Highly recommended.

This Battery Tender has been working great thus far. I primarily use it to keep my RV Batteries charged when stored throughout the winter months. I will occasionally use it for my lawnmower battery. I docked it 1 star simply because it wouldn't charge a Lithium Motorcycle battery. I connected it and after powering on the Tender, it automatically selected AGM. I tried to manually switch it to Lithium, but it wouldn't switch. After doing some Google research, I found that many people have issues getting the Tender to charge Lithium, even though it clearly says that it can charge it. It may have charged it on the AGM setting, however I didn't want to risk it on such an expensive battery. This Tender works great for most applications, but if you're looking to charge Lithium, I would go with a Lithium specific charger for it.

Lite weight

Although the specifications for this product say that a fully dead battery cannot be charged, that this product just maintains charge. I did charge a dead car battery twice. It takes a special procedure, but no extra hardware.The reason that it does not work to simply plug in the Battery Tender, set battery type to AGM (normal car battery), set voltage to 12V, and then attach and charge when battery is dead is that the Batter Tender protects you from connecting the wrong way around to the battery by looking for some non-dead voltage from the battery, so that it can double check that you connected the black negative cable to the black negative battery terminal and the red positive battery cable to the red positive battery terminal. If the battery is dead, it cannot double check you and will pretend for a few minutes to charge the battery, followed by the upper-left blinking light of charging stopped.How to charge dead car battery using just Battery Tender:(1) Disconnect car battery positive red terminal from car electrical system by loosening the clamp and removing the cable. The Battery Tender for me failed to charge to 12V with the car connected, because the car electronics drew more power than the 12V Battery Tender electronics could supply in the case of low battery power.(2) With Battery Tender battery cables not connected yet, plug in the Battery Tender.(3a) Set battery type to AGM (normal car battery).(3b) Set voltage to 6V. This is key. Battery Tender does not double check correct polarity for 6V and will push current no matter what.(4) Attach negative black Battery Tender cable to negative black battery terminal.(5) Attach positive red Battery Tender cable to positive red battery terminal, which remember you have already disconnected from the car's electrical system.(6) Double check and triple check steps (4) and (5) to be absolutely sure you connected black to black and red to red. If you get this wrong, unspecified bad things will happen. This time the Batter Tender will not double check you.(7) The Battery Tender will indicate charging with solid upper right green light.(8) About 4 hours later the Battery Tender charging solid upper right green light will go off, and lower right solid green light will indicate full charge to 6V. Do not believe it. The battery voltage is 6V, but it is still lacking amps, and the slightest load will drop the voltage back down below the level that the 12V charging below will succeed.(9) After about 12 hours the Battery Tender will still indicate the same fully charged 6V, but by now enough additional power has been added to proceed confidently.(10) Disconnect the Batter Tender from the car battery.(11) Unplug the Batter Tender until the lights go out.(12) Plug the Battery Tender back in.(13a) Set battery type to AGM (normal car battery).(13b) Set voltage to 12V. This is key. Battery Tender having charged the battery to 6V will now be able to double check that when you connect it to the car battery that you are doing it the right way around.(14) Attach negative black Battery Tender cable to negative black battery terminal.(15) Attach positive red Battery Tender cable to positive red battery terminal, which remember you have already disconnected from the car electrical system.(16) Double check steps (4) and (5) to be sure you connected black to black and red to red, but now the Batter Tender will double check you.(17) About 4 hours later the Battery Tender charging solid upper right green light will go off, and lower right solid green light will indicate full charge to 12V. Do not believe it. The battery voltage is 12V, but it is still lacking amps, and the slightest load will drop the voltage back down below the level that car start will succeed.(18) After about 24-30 hours the Battery Tender will still indicate the same fully charged, but by now enough additional power has been added to proceed confidently. 12 hours is nowhere near enough. A day is a really long time, but remember that the Batter Tender was never intended to charge, just maintain, so it's output amperage is low. Although it will in time accomplish a battery charge, it will take a long time. Do not rush this step.(19) Disconnect the Batter Tender from the car battery.(20) Taking electrical safety care that you now have a live, powerful car battery, connect the car electrical system cable to the red positive terminal of the car battery.(21) I had to wait about 10-20 minutes before my car would respond. I think that some capacitors had to take time to charge before the car's electrical system was well again.(22) I first pushed the button for just the car's accessory mode to let all the systems reset themselves. The center console did some initial loading that it does not usually do.(23) Turn off the car, then start engine. All should be working for the moment, unless your radio thinks that with the power off for so long that it has been stolen and asks for an authorization code to work; your car dealer should be able to help you there; I did not experience this.(24) Drive the car for a half-hour or so to give the alternator time to top off the car battery.