what can hurt your electric car's mileage

 

There's a good chance you're looking very closely at various EVs and their estimated range ratings. Before you sign on the dotted line for an EV, new or used, there are some things you should know so you're not surprised by a car's real world range.

© Provided by Roadshow As with combustion-engined cars, estimated energy efficiency of an EV can vary from what's on the sticker, sometimes by a lot more than it varies in combustion cars. EPA

Cold weather 

Cold weather can substantially drop your EV's range. The Idaho National Labs found that an EV can lose 25% of its rated range at freezing temperatures. As an example, that could drop a current 2021 Nissan Leaf from 149 miles of range to 112, in essence setting it back five model years. Going the other way, that study also found that fast charging was 35% less efficient at freezing temps compared to its efficiency at 77 degrees. The newer an EV you buy, the better it's likely to handle cold weather due to improvements in battery management technology, a good reason to assess a used EV carefully before deciding it's a bargain.

© Provided by Roadshow Temperature affects both the energy capacity and voltage level of the type of single cells that are the building block of EV battery packs. Richtek

Heating and cooling

Heating and cooling an electric car's cabin isn't trivial. Unlike combustion-engined cars, which have a vast source of waste heat for warming and belt-driven parasitic accessories to compress refrigerant for cooling, electric cars have to use electricity to do both.

A 2019 AAA study of five models of electric cars found that 20-degree weather can shorten an EV's driving range by 41% when the heater is on, a combination of that draw and the temperature challenges we saw above. On the other end, the AAA study found that range dropped by around 17% on a 95-degree day, largely due to use of the air conditioning system.

EV makers are rapidly innovating in this area to reduce range penalties from keeping comfortable. The Nissan Leaf now uses a heat pump system like you might find in a mini-split HVAC unit in your home, and Jaguar recently won an engineering award for combining such a heat pump with a system that harvests heat from the system that cools the main battery and motor in the I-Pace.

© Provided by Roadshow The Nissan Leaf uses a sophisticated heat pump system, unlike the more common resistive heating technologies that sapped power from early EVs. Nissan

Pro tip: Precondition the climate in your car before you leave while it's still on the charger so the grid does the heavy lifting of heating or cooling.

Stop and go

We're not talking about stop-and-go traffic but the way you make your EV stop and go. Electric cars have regeneration, which momentarily turns their electric motors into generators that charge the battery and slow the car. That's due to the electromagnetic drag required by the regeneration process. Take advantage of it by setting your car to its highest regen setting and doing as much braking as possible by just lifting off the accelerator. It takes some getting used to, but can make a real difference that will show up instantaneously on your dashboard range gauge.

Battery age

This is the main reason a used EV may not be a bargain. First, battery technology is improving rapidly, offering greater storage capacity at the same or lower prices each model year. Secondly, electric car batteries gradually lose capacity as they're used, not unlike every other battery-powered device you own. Combine these two factors -- lower capacity when new, and reduction of that capacity from being used -- and you can end up with a "bargain" EV with real-world range that's only in the double digits. If that's all the range you need, you should certainly consider buying a used EV that costs less than an electric bicycle. Otherwise, don't be cost foolish and end up with a car you hate because you have to worry about its range all the time.