TAKING STOCK – TIME TO LOOK AT ELECTRIFICATION SAFETY
Long ago on 10th December 1997 Toyota introduced the first generation of Prius that went on sale in Japan only with many aspects completed largely by hand from electric motor winding to assembly of the body. The second phase from 2000 to 2003 was sold in selected markets including the UK and featured the first pouch cell battery technology from Panasonic. The technology was not originally created to reduce tail pipe emissions – the primary objective was to build a vehicle with improved fuel economy, much as competitors such as Honda did with the IMA technology, for Japan. The domestic market did not like diesel engines in passenger cars, but a bonus was the ability to sell the technology with subsequent Prius generations into key markets such as California.
The clever parts included a transmission with a generator/motor as well as a traction motor, which allowed the system to use the engine or electric only drive as the system demanded – a parallel hybrid. Many companies were very interested in the transmission technology and undertook licencing agreements or joint ventures. It wasn’t until 2010 that a viable alternative appeared, which came from GM as the Chevrolet Volt, or Vauxhall Ampera as we know it. Of course, it was not able to ‘power split’ in the same way as the Toyota system, with direct drive from the engine to the wheel only possible at elevated speeds.
While hybrid drive existed way before Prius and other Japanese manufacturers were on the very same development path, the idea grew.
Another vehicle which emerged in 1996 was General Motors EV1, which had a profound influence on battery electric vehicles. The battery technology was upgraded in the second phase of 440 units, and it was unashamedly a two-seat commuter car. Honda created a more sophisticated version of the idea as the first Insight, using the IMA hybrid drive technology. The Honda had an aluminium intensive body structure and unique powertrain, whereas the EV1 had a low-tech handmade body with these features:
- Aerodynamic driven exterior form.
- Heat reflective glass to reduce HVAC power consumption.
- The first application of an automotive heat pump.
- Groundbreaking traction motor and high voltage power technology.
Setting things going
All of these vehicles were seen at the time as a ‘side show’, answering a question that few asked. However, EV 1 was to become the bedrock for numerous BEV start-ups, building on the groundbreaking architecture that GM laid down – with direct links to, for example, Tesla. The technology has evolved greatly from those early beginnings, but the use of simulated three phase high voltage power for the traction motor and the reverse transmission from AC to DC for regenerative braking, was born in EV1.
Why did GM try so hard? In essence the battery technology was not in the right place, so to make an effective vehicle all energy losses had to be minimised. Hence for quite a while the aerodynamic driven exterior made from hybrid drive synonymous with ‘Prius’, much to the frustration of Toyota.
The tell-tale of great engineering is the ability to have very sophisticated systems where everything is done for a reason, which is apparently simple to use and repair.
This is what we will explore.
Rate of change increasing exponentially
The rate of change across the electrification subject is break-neck as manufacturers work hard to minimise tax penalties, meet production/import quotas, meet ever-changing demands for reduced or zero tail pipe emissions – and try to make a profit. The result is the after-market and the collision repair business sis on the receiving end of this.
Conversion of existing large investment platforms to electrification, resulting in high voltage systems being installed in all sorts of unusual places.
Creation of dedicated scalable large investment platforms in parallel, pushing cash flow and profitability to the edge.
Ever changing component upgrades to achieve better performance in current production vehicles – yes, that includes the biggest, most expensive single item especially on a BEV, the battery, with no compatibility with previous models.
From a very small evidence base, we can already see a 2012 Nissan Leaf is likely to need a complete battery rebuild and revised cooling system whereas a 2012 Tesla Model S will be mostly intact, but can suffer from catastrophic failure of motors, the traction battery and even the power controller. In other words, reliability trends have not been this make/model specific since the 1970s.
The elegance
Due to parasitic losses from an ever-growing number of 12V body systems, the problem of battery depletion after a few weeks has become something of an epidemic over the past two decades. Add to this the fixation on electronically activated door handles, and the apparently random scattering of high voltage system components, we have a perfect mess.
Part of the solution is to allow the 12V battery to draw from the high voltage battery – if it has one – while the vehicle is parked/stored. This idea is now extended to allow the high voltage battery to draw energy from the 12V battery if required. In other words, setting the drive system to ‘power down’ via the instrument panel does not mean high voltage isolation.
Toyota addressed this very issue, starting with Prius 1. The 12V battery was the master, so if it was disconnected the high voltage battery would be isolated. To add security, a ‘service plug’ on the high voltage battery system ensured isolation could not be bypassed. Now, it could well be advantageous to have the ability to keep the battery control module alive to permit post impact system cooling, but at the point the vehicle needs to have the high voltage pack isolated it should be straight forwards.
Perhaps it’s time to lobby for standardisation of a ‘kill switch’ location, leaving engineers to manage how that works, but ensuring the safety of everyone who needs to work on electrified vehicles. Meanwhile, vehicle specific research has never been more important.
Story by Andrew Marsh
