Electric Vehicle Charging Science
Why charging to 100% is slower and more expensive than you think, and how to preserve your battery life.
The 'Charging Curve' Reality
Unlike a petrol tank that fills at a constant rate, EV batteries charge like a theater filling with people. The first 50% is fast because there are many empty "seats" (ion sites). As the battery reaches 80%, finding an empty seat becomes harder, and the charging speed must slow down significantly to avoid overheating the lithium-ion cells.
The Mathematical Model
Thermal and Conversion Losses:
No charging process is 100% efficient. When charging at home (AC), your vehicle must use an onboard converter to turn the wall's AC electricity into the battery's DC energy. This process generates heat, which is "lost" energy. DC Fast chargers do this conversion outside the vehicle, but still lose roughly 5% of energy through cooling the massive charging cables.
Sustainable Mobility Toolkit
- Fuel Cost Calculator – Compare against petrol costs.
- Electricity Bill Calculator – Understand your household load.
- Vehicle Mileage Calculator – Track energy efficiency per km.
Frequently Asked Questions (FAQ)
Is it cheaper to charge at night?
Many utility providers offer "Time-of-Use" (TOU) rates where electricity is significantly cheaper between midnight and 6 AM. Charging an EV at night can often be 50% cheaper than charging during the evening peak.
Why is the last 20% so slow?
To protect the long-term health of the battery, the Battery Management System (BMS) drastically reduces current as the voltage limit is reached. Most experts recommend charging to 80% for daily use and only going to 100% for long road trips.