What is a Battery Tender and How to Use One

The Battery Tender Junior is super versatile and extremely budget-friendly. For a low price you get the tender with a pigtail lead that wires directly to the positive and negative terminals on your motorcycle’s battery. It has a two-prong plug that allows you to quickly connect the other end to the Battery Tender Junior eliminating the need to pull the seat or cover to the battery. The main unit is a heavy two-plug adaptor that will work for either 6 or 12 volt batteries, and also includes the plug-in “alligator clips,” red and black positive and negative leads that complete the circuit to the battery. The Junior operates at a light 750 milliamps DC (or .75) so it is a gradual charge. It is a completely automatic process. Leaving it connected for a long period of time will not hurt the battery, but the battery and charger should be checked for normal operation if charging for an extended amount of time.

There are two types of grounding systems, positive and negative. The most common is a negative ground system where you connect the positive (red) alligator clip to the positive (or +) battery post, then connect the negative (black) alligator clip to the vehicle chassis.  You should not connect to the carburetor, fuel lines, or thin sheet metal parts, but rather a heavier gauge metal part of the frame to insure the best connection and grounding. Then connect the AC power plug to the outlet. For the less common positive grounded systems you would connect the negative (- or black) alligator clip to the negative post first, connect the positive (red or +) to the vehicle’s chassis, then plug the AC power in last.

There is a single “Status” light on the Battery Tender Junior which is either red or green, and three primary charging modes. First is “Bulk Mode” which is full charging power, with a constant current increasing the battery’s voltage. The battery for this mode should be from 0% (dead) to 75-80% charged. The second mode is called “Absorption Mode” which is high constant voltage with decreasing current, and battery status from 75-100% charged.  The third mode is “Storage/Float” or “Maintenance Mode” which would be low constant voltage, a minimal charge current, and a battery fully charged at 100%.

The status indicators of red and green tell the story of what’s going on in the Junior tender. If there is neither a red or green light this is an abnormal condition showing the charger is not properly connected. With a red light flashing, it shows there is power available and the computer in the charger pack is working properly. If the red light continues to flash it means voltage is too low (less than 3 volts) or your alligator clips are not connected properly. A steady red light shows a good connection and the charger is properly charging the battery. When the battery gets to an 80% charge, the green light will flash and the battery can then be used if necessary. A solid green light means charging is complete. You are done and it’s time to ride! If you do get an alternating red/green light, however, it indicates the battery may be sulfated or there is a poor connection between the charger and the posts.

One great thing about Battery Tender brand chargers is some of their special features. The Junior is spark-proof, which means no voltage can be developed until it is properly connected. There is also short circuit protection, meaning incorrectly hooking up the terminals backwards will not hurt the battery. As you may know this can be a disaster when jump starting incorrectly, causing sparks and sometimes even an exploded battery! There is also reverse polarity protection that protects the Battery Tender internally against any damage due to hooking it up incorrectly. As you can see, the Battery Tender Junior truly is a really cool tool.

In regards to the time needed to get your battery back to “ship shape,” fully crankin’ status, at the .75 Amps rate it will take approximately 16 hours to get back to 80% capacity. Keep in mind when using the Junior, like the tortoise, it ain’t fast, but it will get your battery there. I used mine to charge my Yamaha Morphous 250 scooter, which was dead as a doornail, and the Junior came through like a champ, especially after trying my friend’s “trickle charger” twice.

You’ll need a battery tender any time you find your bike going “click click click” when attempting to start it up like my Morphous did. If you use the Battery Tender Junior and keep it hooked up on a regular basis, it can save your electrical system as it keeps a steady current to the bike but in a very gentle way. I used it to not only get my scooter back up, but also on my 2003 Honda VTX1300S, and for good measure trickled my 1969 VW sandrail custom buggy, too. No matter if it’s a scooter, motorcycle, lawn mower, or even a tractor, if it has a battery, sooner or later its gonna need some extra juice, especially with winter right around the corner.