Chevy Bolt EV Can Charge at 55 kW

The 2017 Chevrolet Bolt EV is capable of charging up to 20-percent faster than it does on today’s DC chargers, according to initial results in a newly published report from a Canadian research institute.

The Bolt’s peak charging rate has been the subject of some speculation. General Motors spokespeople have generally said the Chevrolet Bolt EV and its European equivalent, the Opel Ampera-e, are limited to charging at “50 kW.”

Meanwhile, the owners manual says “when using a DC charging station with at least 80 kW of available power, it will take approximately 30 minutes to recharge from a depleted battery to an estimated 145 km (90 mi) of driving range.”

Today’s DC fast chargers capable of supporting a charging current of 100 amps or 125 amps are typically referred to as being “50 kW” because they support up to a maximum charging voltage of 400 to 500 volts. Actual car battery packs are usually designed to use somewhat lower voltages closer to 350 to 400 volts and so actual charging power is normally somewhat less than 50 kilowatts.

There are no publicly accessible CCS DC fast chargers, the type used by the Bolt EV, capable of over 125 amps today in North America although products from manufacturers like ChargePoint and others are expected to become available for installation later this year.

The new report, by the Innovative Vehicle Institute near Montreal, says the Bolt EV can likely charge at up to 55 kilowatts at a current of up to 150A when plugged into future higher-powered chargers.

Bolt EV battery.

When pressed during an interview earlier this year the Bolt’s Product Manager at Chevrolet, Darin Gesse, stated the car would support a peak current of “about 150A” and a peak charging power of “a little over 50 kW”. Those statements closely match the results found in the new report.

According to the new study as well as anecdotal reports from Bolt owners, the car’s charging current can begin higher but abruptly tapers down to near 100 amps when the battery charge reaches about 53 percent full, drops again to around 60 amps at near 68 percent full, and again to near 40 amps at around 85 percent full.

The researchers worked with the Canadian DC charger manufacturer Elmec to modify an existing 125 amp model for testing purposes. When plugged into a Bolt EV, the modified charger falsely claimed to support 250 amp charging in order to see what current the car would request to charge at.

For their initial round of testing on the modified charger, they started a charging session when the Bolt’s battery was 40 percent full and the Bolt then requested 150 amps.

A lithium-ion battery pack’s voltage naturally rises as it gains charge. When charging at 150 amps, the Bolt’s pack would likely begin charging at a rate of about 50 kilowatts when near empty and then gradually rise until reaching about 55 kilowatts before starting to taper down when the pack reaches just over half full as it does today. At today’s chargers the power typically starts near 42 kilowatts and rises to 46 kilowatts when charging initially at 125 amps.

These peak battery charging rates only apply when the Bolt’s battery cells are 68F or warmer. The battery management system slows the charge rate to protect the lithium-ion battery cells as temperatures get colder.

Since the test only performed a simulated 150 amp charge and the charge began with the battery at 40 percent state of charge it is possible that actual peak charge rates could turn out to be higher or lower.


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