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Articles on Electric Vehicles

October 7, 2015
Paul Gipe

Charging Time: Nissan Leaf on Level 2

To use the Nissan Leaf effectively both in intracity and intercity use, it is wise to know how long it takes to charge to different levels of the the traction battery's capacity. This is particularly true for intercity trips where wait time become critical to the total time spent on travel.

The Nissan Leaf is a Battery Electric Vehicle (BEV). To "fill up the tank" on the Leaf requires plugging the car into a source of electricity and allowing enough time for the car to charge.

Our 2015 Nissan Leaf can store 22 kWh of energy that we can use to drive the car. Another measure of the traction battery's storage capacity is Gids, a unit name after an early EV pioneer. Our Leaf, when new, was capable of storing 292 Gids.

The car reports that it can take up to 4 hours or more from the low-battery warning to a full charge at 220 V. This is misleading as it doesn't account for the actual current used to charge. We've found that the car can be fully charged within 3.5 hours at 240 V on a 40-amp circuit. This is called Level 2 charging. However, this too is misleading as explained below.

Quick charging at 400 VDC is an order of magnitude faster than Level 2. However, Quick Chargers are only found commercially and are not used for home charging.

We use a ClipperCreek HSC 40 for home charging. The HSC 40 is designed for a 40-amp circuit. On such a circuit, an EV can charge up to 32 A continuously. Our Leaf's onboard charger can charge up to 27.5 Ah, or well within the range of the HSC 40.

After acquiring and installing LeafSpy Pro, I measured the charging of our Nissan Leaf on our home circuit. LeafSpy uses data from the car's CANBUS that the dealer uses to service the car and reports the data to an app on a smartphone. The app works amazingly well--even on my Blackberry!

I've posted two charts of two charging sessions. Both report similar findings. The car charges at its maximum capacity--6 kW to the traction battery--for 2.5 hours before it begins tapering the charge. During the taper charge, the charge level drops off dramatically.

This is important to know if you don't have much time to charge or you want to limit the amount of time charging, say, when you're on an intercity trip. You can raise the traction battery's State of Charge (SOC) 60% within the first two hours and 80% in two and one-half hours. That is, if you want to only wait while the car is charging at its maximum rate, you need wait no more than 2 to 2.5 hours. Why wait for the car to finish charging when it is only charging at 1 to 2 kW or even less.

The examples here are most applicable to charging at an RV Park on a 240 V, 50 A circuit with a Jesla portable charge system, an EVSE (Electric Vehicle Supply Equipment) in the jargon of the trade or at a 240 V home charging station on at least a 40 A circuit. "Your performance may vary" if you don't have these conditions.

For example, assume you arrive at an RV Park with 20% SOC. Also assume that the RV Park has a NEMA 14-50 receptacle and you have a Jesla EVSE with you and that you need 60% SOC to get to your destination. In two hours you can raise your SOC from 20% to 80% then drive to your destination with 20% remaining as a reserve. Similarly, if you arrive with only 10% SOC, you can charge for 2.5 hours and reach 90% SOC.

The two accompanying charts are slightly different. The first shows the SOC as reported by LeafSpy. The second shows the SOC as a percentage of the Gids available relative to the Gids available when the car was new (292 Gids). The latter chart is more relevant as it is the total amount energy store in the traction battery that moves the car. The SOC itself doesn't tell you how much energy is available, only the percentage of charge remaining.

The second chart also displays the tapering charge, which isn't needed all the time. When you're in a hurry, as on a road trip, you don't need to tapering charge.



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