If the Bosch 12V battery does not accept charge that does not always mean that the cells are damaged.
Sometimes the system that manages the battery simply gets stuck and you only need to reset it so that it works again. I experienced that with my own Bosch battery, when the charger stopped recognizing it but these three methods successfully revived it.
To restart the battery, you need to use another working Bosch 12V battery to jump-start the dead one. Take a second battery that is in good shape and able to receive charge. Place the batteries on a workbench before starting the process.
How to Reset a Bosch 12V Battery: 3 DIY Methods
Before making any connections, find the positive and negative terminals on both batteries. When the terminals are identified, take some short cables with ring contacts to connect the two batteries together.
Connect the positive terminal of the good battery to that of the dead one using a red cable. Then connect the negative to the negative using a black cable. Make sure that the ring contacts sit flat on the terminal of the batteries, so that there is good electrical contact between them.
The connection between the two batteries must last around 15 seconds. In that time the good battery passes a bit of voltage to the other, which can restart its circuitry. Carefully watch the cables during the process, and if they start to smoke or warm, disconnect everything immediately.
After that time has passed, remove the short cables from both batteries using plier. From that moment, the dead battery gets enough voltage so that the charger notices it. That indeed helped for the battery that I used.
The second method is basically the same, except that it uses a 12V battery of another brand instead of another Bosch unit. I took a DeWalt 12V lithium-ion battery for this example, because that was what I had. Any 12V battery works, if it is fully charged and in good condition.
The positive and negative terminals on DeWalt batteries are clearly labeled on the contact side. The positive terminal marks B+ and the negative B-.
The setup stays almost the same as before. Use a cable to connect the B+ of the DeWalt battery to the positive terminal of the Bosch unit. Then connect B- to the negative terminal of the Bosch.
Leave the batteries connected for the same duration as the first method. The voltage passes, which restarts the BMS of the battery.
For the third method, use a DC power supply instead of another battery. This allows better control of the voltages and currents that you apply to the dead unit. The Wanptek DPS3010U power supply is needed for that restart process.
Set the voltage of the power supply to 12V and limit the current to 1A. Get a reading of 12.00V and around 1A before connecting anything to the Bosch battery.
From the power supply, connect the positive cable to the positive terminal of the Bosch battery. Then connect the negative cable to the negative terminal. The cables of the power supply have alligator clips, which makes them easier to attach to the terminals compared to ring cables.
After connecting, the reading on the power supply shows that current goes into the battery. It started at 0.136A and settled at 0.120A, when the battery electronics started to receive the charge. The power use was about 1.4 watts.
Hold the connection for the same duration as before.
Disconnect the cables from the poles after that. Use pliers to remove the connections, because the poles were tight and the alligator clips barely came off. By that moment, the dying Bosch battery got its voltage back and the control system restarted.
