Following on from my last post I have been thinking in a bit more detail about how charging our electric car might fit in to an automated energy management system for our home.
I have always thought that to charge the electric car using surplus solar power I needed to have a car charger that could vary the power to the car as the amount of surplus power varied. As the sun came out so there is more surplus power so there is more power available for the car to charge and so the charger would then have to be able to sense the fact that extra power is available and then to switch the signal to the car so that is stepped up its charging rate. Conversely, when the cloud covers the sun so there is less surplus power available and so the charger must step down the charging rate.
If you have no battery storage then this is precisely what is needed to ensure that the car charges only, or mostly, with surplus solar power.
However, by adding a battery storage system the need to tightly control the charging rate to the car is reduced or even eliminated.
If we focus our efforts on always charging the batetry storage with the surplus solar power then we always will have that power available to either use in the house or to charge the car. As the battery system will be able to supply the car charger at full power (15A or 30A) we can then just use the standard car charger without the need for a stepped charging rate. The battery storage system is then always topped up with surplus power whenever surplus is available. Power to the house or to charge the car (same thing really) is always supplied from the battery whilst the battery has power available.
So, at the moment, I don't believe I will need any kind os special car charger in this system. The important aspect of the system will be to have a control system that can always dump surplus solar power into the battery storage and to ensure that the system can always provide power from the battery storage before importing from the grid.
At the moment his is just a set of requirements… I have no idea just yet how to achieve this – if you think you can help then please get in touch either with a comment below or by email/Twitter etc.