The use of batteries in photovoltaic systems differs from the use of batteries in other common battery applications. For photovoltaic systems, the key technical considerations are that the battery experience a long lifetime under nearly full discharge conditions. Common rechargeable battery applications do not experience both deep cycling and being left at low states of charge for extended periods of time. For example, in batteries for starting cars or other engines, the battery experiences a large, short current drain, but is at full charge for most of its life. Similarly, batteries in uninterruptible power supplies are kept at full charge for most of their life. For batteries in consumer electronics, the weight or size is often the most important consideration. This section provides an overview of the critical battery characteristics or specifications, including battery voltage, capacity, charging/discharging regimes, efficiency, etc.