Little demand for DC charging

Azure Dynamic, which produces the batteries for the Ford Transit Connect Electric, doesn’t believe there is yet a significant market demand for DC charging.

All charge and discharge cycles affect battery charge capacity over time. Valence, which supplies batteries for Smith Electric Vehicles, predicts 3% to 4% degradation for every 600 cycles (ie two years of daily use). Battery capacity fades gradually.

Ian Goodman, chief executive at LifeBatt, which produces batteries for Ashwoods hybrid vehicles, says customers should understand battery life in terms of their individual needs. Smith, for instance, says its batteries should retain 80% charge after eight to 10 years.

“That’s just quoting battery specs however. It makes more sense to say that a battery should handle 100,000 miles, for instance, at 100 miles per day; after that it may handle 80 miles a day.

In fact, if the user never does 80 miles in a day, they won’t notice the difference. Manufacturers should explain this stuff to the public better.”

Goodman says current batteries could be engineered in mileage increments to fit in the same package but it isn’t cost-effective for manufacturers to do so.

“NCAP testing in particular is very expensive for EV batteries, because there is insufficient experience in the industry yet to know appropriate ways of testing for guaranteed results. We are working towards industry standards, but the industry has yet to decide what size plug to put on a vehicle – goodness knows how long it will take to agree passenger safety standards.”

The rigours of testing and volume production mean new battery technologies will be slow to market. Lithium ion will probably dominate the field for the next five years but there are technologies in labs now with huge potential.

“There are new electrolytes which will open up performance,” says Paterson. “Annode technologies such as silicon alloy could increase energy density and be cheaper. On the cathode side, traditional chemistry will only take us so far.

“There are blue sky projects such as lithium sulphur which will offer 300-400kWh a kilo or Lithium Air which could offer five times the energy density.”

Huge potential of Lithium Air

Currently Lithium Air doesn’t exist outside the lab, but it has huge potential. “We are 15-20 years away,” says Paterson.

LifeBatt thinks metal air technologies could deliver faster than this.

“None of the existing vehicles use current cutting edge technologies,” says Goodman. “We think Lithium Air will come in in the next five to 10 years.”

One of the areas of contention over EVs in fleets is residual value. CV operators such as TNT have written their EVs down aggressively, expecting them to run on for two or three years further, and for the battery itself to have a residual value at the end of the vehicle’s life.

The used market remains unconvinced of the residual value of EVs, however, based largely on concerns about battery life.

Axeon is involved with various projects to investigate the second life for batteries and cost-analysis around recycling or disposal.

Paterson says: “We have not been running them long enough to fully understand the economics of degradation. However, it may be more sensible to recycle them than to put them into a second life as capacitors.” nd the challenges

Battery management

Modern lithium-ion batteries have intelligent management systems which monitor and manage performance. This battery management system (BMS) is the next biggest cost in the battery pack after the cells, accounting for 10% of the total.

The BMS does several things: it provides a safety mechanism to protect the battery from significant over-heating by limiting access to power until the battery has cooled; it
regulates the balance of charge between cells and modules; and it communicates between the vehicle, the battery and the charging unit.

“The weakest cell in the pack determines performance,” says Axeon’s Paterson. “So the BMS can move energy around between cells to give average performance.”

He says that the cost of developing BMS will drop faster than cell prices once we reach volume production.

Many batteries today are modular in design, with more power being added simply by adding another cell pack.