How does a battery decide when to charge and discharge?
The evening rush. The battery started the day full and is now at 34%. Two cars arrive at once.
The controller decides how much to give now and how much to keep for the next hour.
The questionWhat does the controller weigh, minute by minute?
A composed day. The battery discharges at the peaks, refills between them and overnight, and never drops below its floor.
Four rules of a typical controller
- Discharge when the chargers need more than the grid connection offers.
- Refill whenever demand is below the connection, using the spare capacity.
- Keep a reserve for the next expected peak, so the evening rush does not find an empty battery.
- Follow prices where useful: refill more when electricity is cheap, for example at night.
Forecasts make it better
A controller that knows when the busy hours come, from past days, holidays or traffic, can keep the right reserve. One that also knows tomorrow's electricity prices can refill when energy is cheap. The prices are explained in Energy and grid integration, stop 05.
Check your understanding
3 questions. Answer all of them to complete this stop. Each answer explains itself.
When does the battery refill during the day?
Any spare capacity of the connection can refill the battery.
Why does the controller keep a reserve?
Planning for the evening rush avoids running out at the worst moment.
What helps a controller choose when to refill?
Knowing demand and prices ahead lets the controller refill at the right time and price.