How Does ‘Phantom Drain’ Affect EV Batteries?

Paul MilnerApril 15, 2022

Electric vehicle range is one of the most important aspects for any driver or fleet manager to consider when adopting EVs. It is imperative when it comes to planning the logistics behind daily vehicle routes and charging schedules, as a lower range will mean shorter, inefficient routes and more frequent charging needs.

EV fleet managers will also have to consider the various situations and factors that cause batteries to drain faster or inhibit efficient charging. Extreme temperatures is one of these factors. For fleets operating in extremely hot or cold weather conditions, battery capacity and charging speed can be negatively affected. These effects can be permanent and lessen an EV’s range over time.

EV drivers are now noticing another phenomenon, called phantom drain, affecting their battery performance and fuel efficiency.

What is phantom drain?

Phantom drain, also called vampire drain, occurs when energy is lost from a battery when the vehicle is not in use. It was first observed in a study conducted on a 2013 Tesla Model S which showed that on-board electronics contributed to a range loss of up to five miles when vehicles sat unused and unplugged for 18 hours or more.

Why does this happen? There are multiple contributing reasons. Basically, when EVs are turned off, they are still using standby power to run features such as power locks, battery climate control and third-party apps. Most EVs have a small lead-acid battery which is responsible for powering some essential functions, but the main vehicle battery still suffers phantom drain from other sources.

While five miles of lost range might not pose much of a threat, the constantly advancing technology and third-party applications in EVs hold the potential to drain even more battery power going forward. This drain from energy-intensive technology in combination with external factors like extreme weather can amplify the overall decrease in battery performance.

What does this mean for EV drivers?

Phantom drain can have serious implications for fleets that use their EVs infrequently. This is easy to understand when you imagine how it would be if ICE vehicles lost a gallon of fuel to evaporation every day that they sat unused. Over the course of several months or a year this would quickly add up to a substantial amount of excessive fuel consumed.

To combat this, many drivers will leave their vehicles plugged into charging ports until they are ready to be driven. This tends to muddle EV charging data at an event level, however. Many small charging events keep vehicles topped off, but for business purposes they should be aggregated into a single charging event representing the total amount of energy consumed during the vehicle’s time plugged in.

EV drivers and fleet managers can take some preventative measures, however. Turning off any nonessential features, or even switching your vehicle to energy-saver mode, can be a good first step. Additionally, keeping your car warm whenever possible can be a huge help in preserving battery performance. Extremely low temperatures are a major culprit for weakened battery capacity, so keeping cars in a covered garage can help prevent batteries from exposure to freezing temps.

All in all, phantom drain should not be a deterrent for those considering switching to EVs, nor should it be a major cause for concern for fleet managers. As lithium-ion batteries continue to evolve and increase in capacity, this slight loss of energy should become even less of a threat.

If you’re interested in learning more about how Utilimarc can help you make the most of your EV performance and charging data, schedule a live demo with our analytics team.


Paul Milner

Senior Analyst

Paul Milner is a senior analyst at Utilimarc. He studied mathematics and philosophy at the University of St. Thomas in Minnesota. Working at Utilimarc for nearly ten years, he helps find the stories and solve problems within complex data sets. See more from Paul


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