It is now historical fact that 100 miles/ 160km range was only attractive to a minority of car buyers because they could not buy and park a second car for the long range that almost all of them needed sometimes. The BMW i3 partly bridged the gap by offering a get-you-home range extender. Now all serious mainstream pure electric car manufacturers are offering at least 200 miles/ 320km range by the rather primitive approach of stuffing in twice the amount of battery and taking heavier trading losses as they gamble on battery prices tumbling. The subcompact C Category car with over 30kWh of battery is becoming the norm.
Certainly battery costs are dropping steadily thanks to redesign, such as silicon anodes with higher capacity cathodes and the building of gigafactories. It is even possible that small cars will become cheaper in pure electric form than equivalent internal combustion vehicles within five years just as that is already true for golf cars today.
However, there could be a temporary shortage of safe, large lithium-ion batteries with acceptable performance as they appear in buses, ships and much else besides and the car demand is by no means uniform in nature. It spans from those that will buy very cheap Chinese city cars with short range to the heavy duty autonomous city taxi cars being designed. We therefore see a place for many approaches and even a niche for a modernised form of the old battery trailer approach as now proposed by EP Tender in France using a petrol generator or, when viable, a fuel cell or post-lithium battery. It would give 500km extra range and be rented on demand. It has a top storage box and will not knifejack. However, it will not obtain more than a small niche in the market in our opinion. As many will lack the parking space, it should perhaps be delivered on demand and that has a cost. It could be a useful adjunct to the autonomous unmanned taxis likely to dominate cities as private cars, autonomou s or not, are increasingly banned or discouraged. Other valuable niche approaches of various sizes include gas turbine jet engines (MACK, a Chinese car etc), rotary combustion engines (Diamond Aircraft etc) and on-board fuel cells (Toyota, Honda, Hyundai, Nicola etc - though most are heavily backing other options too). Mainstream range extension is currently two and three cylinders four stroke internal combustion engines - nothing cleverer - and pure electric cars are coming in fast.
The Proposed Service
EP Tender's analysis is founded on extensive real life data of trips in the US published in this research. It shows that a vehicle with 100 miles range can satisfy 100% of the needs of 9% of the population only. But, if an alternate solution is available during two "adjustment" days (for long distance trips), then 19% of the population is 100% satisfied. The figure jumps to 30% satisfied with 6 alternate days. With a 200 miles EV, 75% of the population can satisfy 100% of their needs with 6 alternate days only.
So, with EVs having a range of 100 to 200 miles, the usage of EP Tender from 2 to 6 times in the year can satisfy 100% of the needs of 75% of car users. And a corollary to this conclusion: carrying a much heavier and much more expensive energy storage on board the EV (battery or REX) is an overkill, making it non-competitive as compared to ICE vehicles, and requires unsustainable subsidies.
Another angle with similar conclusions comes from a research published in August 2016 in Nature Energy. We have extracted the chart on the right, showing the statistical distribution (from real usage data) of the energy demand per day of a car, assuming it has an electric powertrain.
A battery of 19 kWh (Zoe is 22 kWh) satisfies 87% of driving days of the whole population in a year. Adding 20kWh, to reach 40 kWh, satisfies 9% more days. Adding another 20 kWh, to 60 kWh, satisfies 1.5% more days, while going to 80kWh will satisfy another 0.5%, etc. In other words, the marginal utility of a larger battery is massively decreasing, while its cost and weight remains linear, with a major impact on the base platform as well.
We have here a further confirmation that a range of 100-200 miles (batteries of 30-60 kWh) will remain the optimal balance between marginal cost and marginal utility.
The remaining 2.5% to 1% must be satisfied by other means, which is the purpose of EP Tender.
The powertrain modularity we are proposing is a way to increase massively the number of electric miles driven by the whole population, at an affordable cost, and with a much accelerated rate of EV adoption.
Credit and top image: EP Tender
Source: Electric car range winners and losers
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