How Efficient Are Plug-In Cars? Survey Says…

A number of plug-in hopeful firms have been testing their future products in fleets, keeping a close eye on the data coming back as they prepare for their consumer launches or wider availability. One such vehicle, Toyota’s plug-in Prius has been testing for some time now, and while the results of US and European testing hasn’t been publicized yet, Wards Auto reports that the company has disclosed the results of Japanese testing with some interesting conclusions. With BYD and Chevrolet releasing data from their own plug-in testing, we should have the basis for some interesting insights. Hit the jump for more on the lessons learned and the data gleaned from this testing of next-gen drivetrains.

Toyota has long taken a very conservative approach to both pure plug-in EVs and the lithium-ion battery technology that underpins the current generation of pure EVs. And as a result, their test data shows some interesting usage paterns that might not have been publicized by a firm with more skin in the EV gamble. To wit:

Some 45% of users in the Japan test drove less than 20 miles (32 km) a day, so their daily fuel use was zero, [Toyota Europe engineer Rody El Chammas] says. And because they had a 1.8L gasoline engine on board, they didn’t worry about driving further.

Most drivers of the 200 plug-in hybrids in the Japanese fleet trial used the car for business, and Toyota was able to track results of the daily drives on the same route.

It was no surprise the extremes of cold and hot weather reduced the range of the PHEVs. At 32° F (0º C), range is cut in half; above 77° F (25º C), when the air conditioning kicks in, the range sinks again. But in addition to the effects of weather on the draw of electricity, Toyota also found a “traffic jam” effect.

In good weather on the same route, when the drives averaged 19.4 mph (31.2 km/h), the EV range was about 4 miles (2.5 km) more than when speeds were averaging 13.7 mph (22 km/h).

Meanwhile, as TTAC has pointed out before, measuring plug-in hybrid efficiency is a huge challenge given that the vehicles are literally “as efficient as you want them to be.” Or, as the Toyota engineer puts it.

Actual fuel savings depends on how far people actually drive their PHEVs. El Chammas says 19 miles (30 km) a day saves 71% of fuel, compared with a hybrid Prius, and at 31 miles (50 km) a day, the savings is 41%.

In Europe, 75% of daily trips are less than 50 km, he says, while in the U.S. 66% are below that and in Japan it’s 90%.

El Chammas says European testing is beginning to show another new challenge, namely making charging infrastructure available and convenient to PHEV drivers. Problems ranging from vandalism of charging stations to non-EV squatting in charging station parking spots have been issues in European testing, he admits. In my own experience with the Prius Plug-In, which was undergoing US testing as part of ZipCar’s fleet, this is proved to be a real and not-inconsequential concern: my own test results were compromised as a result of the Prius not having been plugged in by the previous user.

Luckily for Toyota, it has found that Prius PHEV drivers don’t worry too much about charging, as efficiency is still pretty good without a full charge. But at BYD, which has released data on its Chinese pure-electric taxi tests to GreenCarCongress, they’ve found that rapid charging has yet to make a serious impact on battery life or power. This is significant in the sense that “normal” charging of a pure EV can be incredibly time-consuming, while rapid charging is widely considered to have a negative impact on battery life and power (for example, Nissan says slow-charging its Leaf EV takes 21 hours, while rapid charging will take 10% off of the battery’s life and power by the end of its life). But, reports GCC

BYD said that the most important finding in the e6 fleet testing was that there has been no noticeable energy drop—both driving range and battery performance has been stable in rapid-charging conditions over the 1.73M miles tested.

Of course, that’s based on 50 Shenzhen-based e6 taxis, so divide those total miles by 50 and you find that each has gone an average of 34,600 miles. It’s promising that BYD has not yet found any negative impacts from rapid charging the iron-phosphate batteries, but we’d want to see at least four times that mileage before we declare regular rapid charging to be free from battery degradation issues. Meanwhile,

According to collected data, the per-car-fuel-savings is more than $1,167 per Taxi per month (driving an average of 400 km per day). BYD’s all-electric Taxis are expected to help Shenzhen avoid about 133 lbs (or 60.4 kg) of carbon-dioxide emissions per day per taxi. This is an equivalent of 2,425,060 lbs (or 1.1M kg) of carbon-dioxide pollution saved by this fleet in the first year.

Unfortunately, BYD leaves a couple of key variables un-fixed, such as the carbon rating for electricity in Shenzhen, as well as an average kW-per-vehicle-mile-traveled number. As a result, the Shenzhen taxi data is less than entirely illuminating. If anything, the most interesting number is the nearly 250 miles per day that the fleet apparently averaged. On the other hand, that number is just a little bit suspicious as it’s exactly the manufacturer range rating BYD gives for its e6.

Luckily BYD redeems itself by releasing some far more revealing data from its Los Angeles-based test fleet of F3DM compact plug-in hybrid cars.

BYD also reported on its F3DM fleet which BYD launched in its first US tests at the Housing Authority of Los Angeles (HACLA). The F3DM can travel more than 40 miles (64 km) all-electric but can be engaged to act as a Hybrid-Electric (HEV) to extend its range up to 300 miles (483 km). The HACLA fleet has now accumulated ~10,430 miles (16,785 km) all-electric and 14,430 total miles (23,223 km); 4,000 fuel-driven miles when extended range was necessary.

The fleet is achieving an equivalent of 88 mpg (2.67 L/100km) and BYD estimates the per-car-savings—even netting out EV charging and electricity costs—is ~70%. BYD’s dual-mode cars are expected to save HACLA about 37 lbs (16.8 kg) of carbon-dioxide per-day-per-auto when driven to the EV range.

Given that Los Angeles represents one of the more extreme driving environments unique to the US market, this data is quite interesting. On the other hand, the fleet is relatively new and has not yet accumulated enough miles to truly test the long-term viability of the F3DM. Considering that driving impressions of the F3DM indicate that it is a relatively immature product by US market standards, we would want a good deal more data before we even thought about putting money down on a BYD.

Meanwhile, Chevy is carefully collecting data from its Volt customers, and spokesman Rob Peterson says he’s encouraged by upticks in the Volt’s efficiency which are showing up in both anecdotal and customer data. From the December launch of the Volt through February, GM says Volt consumers averaged 800 miles between visits to the gas station, and in March that number jumped to 1,000 miles. Peterson says Volt owners now fill up on gas an average of once every 30 days, and that GM will be sharing more data on the Volt’s usage data going forward.