How to Troubleshoot a Battery Tender

by Chyrene Pendleton
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green spray bottle image by Jim Mills from

Since 1989, Deltran Corporation designed battery chargers based on their charger algorithms used on their nuclear submarines and Bradley Fighting Vehicles in the Middle East. Deltran continues to manufacture the Battery Tender, used to charge batteries in boats, motorcycles, ATVs, RVs, automobiles, tractors and most applications. Troubleshooting your Battery Tender will help you locate and resolve problems quickly, saving you time. According to Deltran, most problems you will encounter come from the electrical connections on the battery posts.

Step 1

Disconnect your Battery Tender, then make a solution in a spray bottle of 1 tbsp of baking soda in a cup of water to clean the electrical contacts of your Battery Tender. You will need to clean the Battery Tender if you see the red LED flashing, or if the red and green LEDs take turns flashing on and off. The flashing LED might indicate a poor electrical contact. Spray a clean cloth with the water and baking soda mixture and clean the charger DC output cable, the battery lead posts, and all exposed charger DC metal parts of the output accessories, including the charger DC output cable connector. Rinse the electrical contacts using clean water and dry them thoroughly with a clean, dry cloth.

Step 2

Allow more time for the battery to charge if the red LED of your Battery Tender stays on longer than usual and the green LED does not come on. This usually means your battery is a large one, which takes longer to recharge.

Step 3

Check to make certain you have AC power going to the electrical outlet you have your Battery Tender connected to if you see no LEDs on. Try connecting to another outlet that you know has power.

Step 4

Disconnect your Battery Tender from the battery, and then connect a voltmeter to the battery terminals to check the voltage if the green LED comes on too quickly when you first start charging the battery. This may mean the battery already has a full charge. Turn on the headlights of the vehicle and check the voltage. If you see a 12.7 voltage reading, this will confirm the battery has a full charge; otherwise, a reading under 12 volts, such as 11.5 volts may mean you have a defective battery.

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