ct_engneer:
afremont:
Put a small value, precision shunt resistor in series with the cell and measure the voltage drop across it.In solar battery charging systems every bit of energy is precious. A current shunt is just throwing away energy. Granted that it is a small amount but, if it can be avoided it should be. The use of a Hall sensor would be my first choice. Search ebay and you will find Hall sensors ranging from 5A to 30A .
True, but the first couple of Hall sensors that I checked out used 50mW while operating so you'd have to be careful.