By Pietro Perlo
The recent developments of the bus industry have led to impressive advancements: batteries with two different chemistries have been demonstrated to be capable of retaining 90% of the capacity after 10,000 deep cycles in ultra fast charge up to 400kW1. While the high robustness under several tenths deep cycles is a rather consolidated characteristic of several LTO commercial batteries, the current state of-the-art relies on a new level of system integration offering a radical change on the expectations of road transport. The battery pack is highly thermalized with all cells immersed in a temperature controlled flowing liquid. 12,000 electric buses are running worldwide with over 1 billion km without inconvenience using battery packs with those characteristics. About 1,000 of these are in operation in London2, where two people only maintain the full fleet against the usual 50 people necessary to maintain an equivalent fleet of diesel buses. E-buses developed with batteries priced 700$/kWh would be operated at the same cost of diesel and CNG buses, while e-buses with batteries price 150$/kWh would be cheaper even if the diesel would be free3. Clearly we are facing a situation per which conventional buses will soon become obsolete. Many large cities starting from London will not consider any more conventional buses simply because e-buses cost less with much less maintenance.
Behaviour of battery cells installed in modern buses in service in London (1000 buses) and other three EU member states. Prediction of 8.2 year life expectancy under ultra fast charge (Charging power 400kW, 10Minutes for 66kWh system average charge, each charge between 20kWh to 50kWh) .
Urban EVs installing a 20kWh battery pack could run 100km per charge per each 50% DoD charge. After 10,000 charges the vehicle would have run 1 million km with the battery pack still retaining over 90% of its original capacity. Alternately, the vehicle could be fast charged 3 times a day per 3300 days (10 years) and run over 1 million km maintaining the battery pack at 90% of its original capacity. With a conservative 50% DoD fast charge with respect to what battery technology offers today the perspective is that battery pack after over 1 million km could retain its original performance.
1 http://www.microvast.com/index.php/news/info/70, https://live.ft.com/Events/2016/FT-IFC-Transformational-Business-Awards?=&v=4984103785001
2 Richard, Zhou, High Performance Battery Systems For Emerging Heavy Duty Mass Transit Applications, IDTECHEX Conference, Santa Clara, 17 November 2016.
3 Matt Horton, Maximizing Range & Democratizing Zero-Emission Electric Buses at IDTECHEX Santa Clara, 17 November 2016. Presentation of Proterra inc. the largest US bus manufacturer.
Source: Prof Pietro Perlo
Top image: Wikipedia