Hey everyone! I'm not new to Arduino, but it's been a few years since I last worked with it. Recently, I had the idea of monitoring the current and charge of my Ryobi drill battery, which doesn't have a charge indicator like the newer models. Is it possible to use the battery to power an Arduino and have the Arduino monitor the battery's charge and current draw during use? If so, how can I accomplish this? I've looked at many current monitoring sketches online. Still, they don't consider that the Arduino is monitoring the current from the battery that also powers the board while being used for other purposes, like my drill.
You can use a current sensor like the INA219 or ACS712 to measure the current drawn from the battery.
Is what you care about how much battery life is left? Because that will change depending upon temperature, discharge rate and condition of the battery.
Battery life is usually estimated by measuring battery voltage. You can do that with a resistor tree connected to an analog input on the Arduino.
I would think that an Arduino draws so little power relative to the capacity of a drill battery that you'd have to either wire up an external load or wait a very long time to get an idea of the performance curve.
During use of what? The charger, I hope! Yes, monitor the current. When the initial current from the charger changes to be much less, then you know the battery is charged.