Patent ID: 8294428

Claim:
An electricity accumulating device comprising: a plurality of capacitors connected in series; a plurality of balanced voltage adjusting portions connected to the capacitors respectively; and a control circuit connected to the balanced voltage adjusting portions, wherein the control circuit performs following operations: measuring two voltages (V 1 i and V 2 i, where “i” is 1 to “n”, where “n” represents the number of the capacitors) at different times from each other across each of the capacitors during a non-charge-or-discharge period of the capacitors by using the balanced voltage adjusting portions; calculating an absolute value (ΔVi) of a difference between the two voltages (V 1 i and V 2 i) across each of the capacitors; measuring a first point of time (t 1 ) at which the voltage (V 1 i) is measured and a second point of time (t 2 ) at which the voltage (V 2 i) is measured; calculating a time difference (Δt) by subtracting the first point of time (t 1 ) from the second point of time (t 2 ); calculating a voltage adjustment range (ΔVbi) by dividing the absolute value (ΔVi) by the time difference (Δt) and multiplying a result of said dividing by a specified coefficient (A); determining the balanced voltage (Vri) by subtracting the voltage adjustment range (ΔVbi) from an initial balanced voltage (Vro); and controlling the balanced voltage adjusting portions to make a voltage (Vi) across each of the capacitors the balanced voltage (Vri).