My wife owns a Samsung NX-300 camera and I wanted to use it for longer periods without needing to charge batteries round and round. Unfortunately, this camera can use its microUSB port only for charging – it doesn’t work without a battery and doesn’t charge when powered on. So I had to create a dummy battery.
First, I measured dimensions of a real battery and created a model in Onshape with prepared slots for contact pads (link to my project):
I added contact pads made from a piezo buzzer (thin conductive and solderable metal) and connected them to my power supply.
The nominal voltage of these batteries is 7.4V so I set this voltage but nothing happened. I tried to increase the voltage a little bit but without any effect. There were some small number of mA flowing but nothing serious.
Li-ion batteries use to have a temperature sensor to avoid overheating so I measured the resistance between middle pin and negative pin and it was around 1MegaOhm. I added a 1MOhm resistor between these pins and suddenly my camera started working.
I tested power consumption during recording on several voltages and the power input was still about the same.
On 7V it was showing empty battery but still working. I was brave enough to test even 13V input and it worked but I wouldn’t recommend to use this for a long time. 9V is pretty close to the battery voltage and adapters are easily available. At the end I added a barrel jack connector for my adapter and the job was done.