What is the difference between a normal lead-acid car battery, and a deep cycle battery (used for solar backup power)?
Although both of these are lead-acid batteries, the car battery is designed such that it provides a huge amount of current for a short period of time, needed to get the engine going during ignition. The alternator then provides all the power the vehicle needs, meaning this battery might never ever be drained by more than 20% of its total capacity. However, a deep cycle battery provides a moderately large amount of current over an extended period. This enables it to be get discharged to very high percentages (such as 70%), over and over again. To be able to carry this out, it has thicker plates than the normal lead-acid battery.
