EV Charging: Reduce Power Loss with the Right Cable Length
When choosing an electric vehicle (EV) charging cable, length, weather, and charger efficiency are important factors to consider. While a longer cable can lead to minor power loss, this loss is generally insignificant when weighed against the convenience it provides. Additionally, external factors like weather conditions and the efficiency of your onboard charger can also influence your overall charging experience. This guide explores the trade-offs of using longer cables, the impact of seasonal weather, and how to ensure you’re charging as efficiently as possible.
Cable Length and Power Loss: A Small Trade-Off
It’s true that as the length of a charging cable increases, so does the electrical resistance. This results in minor energy loss, typically in the form of heat, but these losses are generally too small to cause concern for most drivers. Here are the approximate power losses based on typical cable lengths:
- 10-metre cable (32A, single-phase): Approx. 50-60 watts of power loss.
- 15-metre cable (32A, single-phase): Approx. 85-90 watts of power loss.
- 20-metre cable (32A, single-phase): Power loss can exceed 100 watts under normal conditions.
For most EV users, the convenience of using a longer cable to reach a charging point far outweighs the small amount of energy lost. Whether you’re charging at home or in public, a longer cable ensures accessibility, even if your parking spot isn’t ideally positioned near the charging station.
How Weather Affects Charging Efficiency
Weather plays an important role in how efficiently your EV charges, particularly in extreme conditions. Both cold and hot weather can lead to increased energy use, though the effects differ depending on the temperature range.
Cold Weather
In colder conditions, typically below 0°C (32°F), EV batteries become less efficient and require energy for preconditioning before charging can begin. Charging efficiency can drop by 5-10% as energy is diverted to heat the battery, ensuring it can accept power efficiently. The colder it gets, especially below -10°C (14°F), the more energy is needed to warm the battery, resulting in further efficiency loss.
Hot Weather
In hot weather, generally above 30°C (86°F), the EV’s cooling system activates to prevent the battery from overheating. While this uses some energy, the efficiency loss is generally less than in cold conditions. Extreme heat, above 40°C (104°F), may require even more cooling, but the overall impact on charging efficiency remains manageable.
Onboard Chargers and Their Efficiency
Another factor influencing charging efficiency is your EV’s onboard charger (OBC). The OBC converts the alternating current (AC) from the grid into the direct current (DC) your battery requires. OBCs typically operate at up to 95% efficiency, meaning some energy is lost during the conversion process.
The good news is that many modern EVs are equipped with thermal management systems that help regulate battery temperature. These systems can heat or cool the battery as needed, ensuring optimal charging conditions. However, these systems themselves draw power, so it’s important to be mindful of weather conditions and their potential impact on efficiency.
Check Manufacturer Guidelines for Battery Heating and Cooling
Not all EVs have the same thermal management systems, and the way each vehicle handles extreme temperatures can vary. Some models offer battery preconditioning features that allow the car to warm up or cool down the battery before charging. Always consult your vehicle's manufacturer manual to understand how your car’s heating and cooling systems work, as this information can help you minimise energy loss during charging.
Conclusion: Convenience Over Efficiency
Ultimately, the small amount of power lost due to cable length or weather conditions is negligible compared to the overall convenience provided by longer cables or effective battery management. For most EV drivers, the trade-off between minor energy losses and the flexibility to charge in various locations is well worth it. However, staying informed about how your vehicle's onboard systems work and taking simple steps—like preconditioning your battery in cold weather or parking in the shade in hot weather—can help you further optimise your charging efficiency.
By understanding how cable length, weather, and onboard charger efficiency affect your EV’s charging process, you can make more informed decisions and ensure you’re getting the most out of every charge.
