1. The problem statement, all variables and given/known data Suppose we have a circuit represented, which is used for charging an accumulator from a.d.c supply of e.m.f, E1 and internal resistance, r1. If the e.m.f of the accumulator is E2 with an internal resistance of r2, then the equation for the charging current is what? In this question, I want to know how to derive the equation for charging current in an accumulator. 2. Relevant equations I know that there is equation that goes like this: E = V + v E = IR + ir E = I(R + r) I = E/(R + r) But am not sure the above equation relates to my question in any way. Am optimistic that there are other equation that will be fit enough for this my questions. 3. The attempt at a solution E = V + v E = IR + ir E = I(R + r) I = E/(R + r) but I don't think that this my working is correct or is fit for the question. Any help?