The figure on the left shows how the LTC4070 can also be used to regulate series-connected battery stacks. Two LTC4070 devices are used to charge two batteries in series with a single resistor setting. The GND pin of the top device is simply connected to the V_CC pin of the bottom device. The right-hand circuit shows a photovoltaic application for the LTC4070. In this application, transistor Q1 has been added to further reduce the already low quiescent current of the LTC4070 to achieve extremely low battery discharge when the PV cells are not charging the battery.