Deep Cycle vs. Shallow Cycle (Car) Batteries
Back when the renewable energy industry was still picking up steam, people that wanted to go completely off the grid would often have to improvise and make do with car batteries. However, car batteries were never built for this purpose and shouldn’t be continuously drained and recharged (which is what they need to do in a solar panel or wind turbine system).
Car batteries are supposed to be used only for starting and ignition. If you take a look inside one, you will see that they have a large number of thin plates.
These plates have a big total surface area that can facilitate a large number of chemical reactions. When you start your car, these reactions produce the sudden burst of power that is needed for ignition.
Deep cycle batteries on the other hand, have thick lead plates that don’t give much room for chemical reactions. Though they produce less current, they are designed to do so for a much longer period of time.
In essence, car batteries are “shallow cycle” batteries that will quickly burn out when used as storage for renewable power.