How does an electric motor drive the wheels?
The car pulls away from the driveway without a gear change and almost without a sound. Only a soft hum is audible outside.
At the first junction it accelerates smoothly from standstill, with full pull from the first metre.
The questionWhat happens between the battery and the wheels, and where does the hum come from?
The traction battery delivers direct current at high voltage. A DC/DC converter lowers the voltage to charge the 12-volt battery.
Select each part to see what it does.
Few parts, little loss
The path from battery to wheel has few parts, and each converts energy with little loss. The electric motor itself works with an efficiency of over 90%.
The core components are the battery, the electric motor, the and the thermal management; the feeds the motor, a the 12-volt battery, and an converts alternating current from the grid for the battery. The motor delivers its full torque from the start, so one fixed gear is enough for most applications.
Magnets or coils
Electric car motors fall into two main types. A permanent-magnet synchronous motor offers more power density and efficiency, but costs more and uses rare earth elements. There are alternatives without them:
- Induction motors use only electromagnets and need no rare earths.
- Synchronous motors with coils on the rotor create the magnetic field electrically instead of with magnets.
Each type has its own advantages and drawbacks.
A sound by law
Because an electric drive is so quiet at low speed, the EU requires an acoustic vehicle alerting system, . It must generate a sound from start up to about 20 km/h and when reversing, so that pedestrians, especially blind and visually impaired people, notice the car. AVAS has been mandatory for all new hybrid and electric cars since 1 July 2021.
Check your understanding
3 questions. Answer all of them to complete this stop. Each answer explains itself.
What does the inverter do?
Converting AC from the grid is the onboard charger's job, and watching the cells is the BMS's. The inverter feeds the motor.
Why do most electric cars need no gear changes?
A single reduction gear is enough. The motor's wide speed range does the work a gearbox does for an engine.
Why must new electric cars in the EU make a sound at low speed?
AVAS compensates for the missing engine sound up to about 20 km/h and when reversing.
- Inverter Power electronics that turn the battery's direct current into alternating current for the motor, and back when the car regenerates. Glossary
- AVAS Acoustic vehicle alerting system: the sound EU law requires from electric and hybrid cars up to about 20 km/h and when reversing. Glossary
- Onboard charger The converter in the car that turns AC from a wallbox or public AC charger into DC for the battery; its rating limits AC charging power. Stop 04 Glossary
- DC/DC converter The stage of a DC charger that turns its internal DC voltage into the voltage and current the car asks for, moment by moment. Charging hardware, stop 02 Glossary
- Power electronics Semiconductor circuits that convert and control electrical energy: in the car mainly the inverter for the motor, in a DC charger the rectifier and the DC/DC converter. Glossary
- ADAC: Elektroantrieb und Elektromotor, Aufbau und Funktion (2 October 2023): components, torque, one gear, efficiency, battery temperature, gross and net capacity. https://www.adac.de/verkehr/tanken-kraftstoff-antrieb/alternative-antriebe/elektroantrieb/. Checked 13 Oct 2026.
- ADAC: Elektroantrieb und Elektromotor, Aufbau und Funktion (2 October 2023): components, torque, one gear, efficiency, battery temperature, gross and net capacity. https://www.adac.de/verkehr/tanken-kraftstoff-antrieb/alternative-antriebe/elektroantrieb/. Checked 13 Oct 2026.
- ADAC: Glossar Elektromobilität: battery management system, cell-to-pack, DC/DC converter, inverter, onboard charger, state of health, motor types. https://www.adac.de/rund-ums-fahrzeug/elektromobilitaet/elektroauto/glossar-elektromobilitaet/. Checked 13 Oct 2026.
- ADAC: Elektroantrieb und Elektromotor, Aufbau und Funktion (2 October 2023): components, torque, one gear, efficiency, battery temperature, gross and net capacity. https://www.adac.de/verkehr/tanken-kraftstoff-antrieb/alternative-antriebe/elektroantrieb/. Checked 13 Oct 2026.
- ADAC: Glossar Elektromobilität: battery management system, cell-to-pack, DC/DC converter, inverter, onboard charger, state of health, motor types. https://www.adac.de/rund-ums-fahrzeug/elektromobilitaet/elektroauto/glossar-elektromobilitaet/. Checked 13 Oct 2026.
- ADAC: Glossar Elektromobilität: battery management system, cell-to-pack, DC/DC converter, inverter, onboard charger, state of health, motor types. https://www.adac.de/rund-ums-fahrzeug/elektromobilitaet/elektroauto/glossar-elektromobilitaet/. Checked 13 Oct 2026.
- EUR-Lex: Regulation (EU) No 540/2014 on the sound level of motor vehicles, Article 8 and Annex VIII (AVAS). https://eur-lex.europa.eu/eli/reg/2014/540/oj. Checked 09 Oct 2026. © European Union, reused under Commission Decision 2011/833/EU.