Batteries for solar system back-up come in three main types, Lead Acid, Lithium or Tubular Lead Acid. Uses flat plates (basically a car battery) and is very cheap. It only has a life of about three years so no serious solar system installer uses them. Lithium. Very popular as they are small and light. They are actually made by welding many small batteries together although they are very reliable. They have a life of between five and ten years. Their light weight means they fit neatly on a shelf and they are ideal for transport with many scooters using them Tubular Batteries. Actually a type of lead acid battery but modern tubular batteries have a life of over twenty years with a manufacturer warranty of five years. We prefer them and fit them to all Zeat solar systems. A true “fit and forget” option. Their only drawback is that they are quite large and heavy so are usually installed on the floor. Their weight can be something of an advantage as a thief would probably get a hernia trying to carry one away. Shame !