If you have several gadgets of electronics projects laying around, your probably have a set of various rechargeable batteries including Li-Ion, NiMH, NiCD and of course Pb. And probably you have noticed that there are so many brands and various capacity around in the market – especially Chinese versions that can be doubtfully trusted. One way to clear things out is to sacrifice one charge and test them.

One and reliable way to measure battery capacity is to discharge fully charged battery with known current. If connecting discharge circuit to Arduino – you can get full lab of testing batteries. This way by sending log data to PC you can get a nice charts of discharging current and full capacity. Without going too deep you probably know that different batteries can drain different sources during various discharge phases. Lets say at the end of discharge you may notice that electrical current may be too low for your project and maybe your should choose different one. And of course you can always write true battery A/h with marker and guess no more. Check out this Arduino based Battery capacity tester.