Abstract: A battery charger including a plurality of battery charging sections which are connected in series and a charging current source, said charging section includes at least a first branch and a second branch which are connected in parallel, said first parallel branch includes an electronically controllable bypassing switch, said second parallel branch includes terminals for receiving the positive and negative terminals of a battery and a one-way electronic device which are connected in series, said bypassing switch has a very low impedance when activated or turned-on and a very high impedance when deactivated or turned-off, wherein said one-way electronic device is characterised by a very low-impedance when current flows from said charging section into said battery terminals and a high-impedance when said bypassing switch is activated, the battery in the charging section in which said bypassing switch is activated is substantially isolated electrically from the charging current, the other charging sections and t