hi, just brought a few battery's (18650's Li-ion) for a project brought them from china im pretty sure they are not counterfeit as they seem to be heavy, another one i brought seemed very light i guess that one has a much lower capacity.

anyway just wondering how to work out the capacity of it, im wondering if i could work out the capacity of it by the charging rate? im charging it at 500ma, so if it takes 6 hours to charge can i assume its roughly 3000mah battery? or can it only be worked out on the known current discharge rate? thanks