It is not economical to use car batteries to feed into the grid. The batteries are not designed to be cycled that often. It's better to use purpose built batteries.<br>Alinta has a few renewable assets in remote Western Australia and has a gas turbine for this particular reason. They are now going to replace the gas turbine with batteries to reduce their costs.<br>Car batteries and grid/home batteries are similar, but there are enough differences that they cannot be interchanged.