Had a Gardena 18V battery pack that teh charger would not recognize at all. The battery pack had been sitting for many month without use, which caused it to fully discharging. When I dropped it onto a charger, nothing happened; the battery pack remain dead.
My idea was to jump start the dead battery by connecting it to a battery that was fully charged and of the same voltage. I found one of another brand that was working to use as the jump starter.
The first thing I did was to identify the positive and negative terminal on the dead battery pack. There are small symbol next to each terminal that makes it easy to identify each terminal.
I used a DeWalt battery for this demo, as it is a fully charge battery. 18V batteries between 18 and 20 volt will work for this jump start technique.
Jump start methods
I connect the positive terminal of the healthy battery to the positive terminal of the dead battery. I did the same with the negative terminal.
I left the two battery connected to each other for around fifteen seconds. During this time, the voltage from the healthy battery will jump start the dead battery. The charging circuit on the Gardena battery tool will only charge the battery if the voltage of the battery is above a certain level. If it is too low, then the battery will refuse to charge.
Some Gardena battery have a different case and buttons than others.
Saw one model that had an orange button and different styling. As long as the battery read 18 volts, the same process will work regardless of the design of the battery.
Another way to jump start the Gardena battery is with a DC power supply. Set the voltage to the same as the battery and use more control over the power source for jump starting the battery.
Adjust the voltage knob to 18 volts and adjust the current to 1 amp. Current control how much energy that the dead battery pack receives from the power supply. Too much energy at once can damage the battery and prevent it from accepting the charge. Slow and steady yields the best result.
Connect the positive lead to the positive terminal of the dead battery. Connect the negative lead to the negative terminal of the dead battery. Make sure that the battery is correctly connect or the battery will be ruined beyond repair.
With the power supply correctly connected to the battery, the power supply will show current flowing into the battery. The current should jump to around 0.3 amp. Allow the battery to charge for fifteen second as in the other method of jump starting the battery with another Gardena vacuum battery.
Once you disconnect the power supply from the battery pack, place the battery back onto its original charger. The charger will recognize the battery and begin to charge the battery as indicated by the blinking green light. Finally!
Place the battery onto the charger and allow it to charge. The blinking green light indicate that the battery is charging and working back to 100% power. A dead battery that was not recognizing the charger fifteen minute prior is now successfully charging.
