I came across a new problem, and this time the subject was a laptop. My mission was to repair an ACER Travelmate 2200 laptop that wouldn’t charge and run on AC power. It would run fine on battery, but when you plug in the AC adapter, it does nothing. It keeps running on battery power.

The problem gets weird when you turn off the laptop. Suddenly it charges the battery. Once the battery is fully charged, you can turn it back on and keep working. However, it would be annoying if you had to do turn off the laptop every time and wait for the battery to recharge.

There is a simple explanation for this, but I didn’t think of it immediately. The AC adapter I was using was not a genuine ACER brand. It was a Toshiba adapter that had the same DC plug. But that’s not the (only) reason why it didn’t work. Even though the adapter supplied the correct voltage of 19V, it didn’t supply the required current. ACER needs 7.1A, and Toshiba only supplies 3.65A, and newer models only 6.1A. For ACER to charge the battery and work on AC power at the same time, you need the exact same current or more. It doesn’t work if the current is less than what’s required. And it’s not recommended to use an adapter from another brand anyway. You should only use genuine parts for your laptop to avoid more problems.

The owner of the laptop lost the original ACER cable and found a replacement, but the Toshiba adapter doesn’ supply the same current. So, for anyone out there who has the same problem, please make sure that your laptop’s AC adapter provides the correct voltage (V) AND current (A).

You can find the required voltage and current details on the bottom side of your laptop.