One of the ongoing issues which is holding back electric truck development is the battery technology available. This is a fast-moving field and new technology is appearing all of the time. This development is crucial, as the way to make them economically viable is for the batteries to be lighter and able to hold more charge, giving the electric trucks more range.
New battery technology seems to arrive about once every three months, but there have not been any quantum leaps in energy density in batteries suitable to be fitted in trucks in the recent past.
“Up until about July last year we had a lot of increases in battery density,” says Joe Di Santo, SEA Electric Sales Director ANZ, who works out of the SEA Electric headquarters in Dandenong in Victoria. “From our understanding the next wave of improvement is still about 18 months away. This means we will have a stability in our product. What we now have is what we will continue to have over the next 18 months.
“At that point we can expect to get more energy into that box and increase the density. We are going to stick with what we’ve got and, instead of doing R&D projects, we can start to pump out some really big numbers of Hino 917 electric trucks.
“Most of our customers understand that buying these trucks is like buying a laptop. Do you want to wait 18 months to get the next technology? At this time, most of the purchases are quite strategic. They have a real marketing initiative behind them, they’re there to promote the transition to new technology.”
Essentially, SEA’s core market is the simple 200km and back to base type application and then recharge overnight. A 20 per cent improvement in battery density would only move the range out to 240km, so this is not a major game-changer for potential buyers.
The technology which is likely to move the market in electric trucks forward is the advent of fast charging. SEA has introduced a fast charging option with its latest trucks. The fast charging system is now available and simply needs a three phase power outlet.
With this kind of technology onboard, the idea of ‘opportunity charging’ comes along. Fast charging the truck up in the driver’s lunch break or while loading can deliver a longer range and improved productivity.
Driver Behaviour and Electric Truck Development
One of the first things anyone will notice when driving an electric truck is just how fast it will accelerate away from a standing start. This was certainly the experience of this driver taking one of the SEA trucks out of the Dandenong facility for a test run. Gentle pressure on the accelerator will give you gentle acceleration, but push it to the floor and the driver’s body is pushed back into the seat by the G-force.
This intense acceleration is because the full torque from the motor is available right from zero rpm all way to cruising speed, unlike the typical torque curve on the standard diesel engine.
This is one of the issues that operators are seeing when they monitor driver behaviour on their electric trucks. The temptation to accelerate fast is difficult for the drivers to resist. Drivers used to diesel trucks around the city are used to banging hard on the accelerator and then banging hard on the brake.
This kind of behaviour is not desirable in either diesel or electric trucks. Controlled and gentle acceleration is good for fuel consumption in a diesel, but in an electric truck it can use up precious watts and restrict range. Similarly, when it comes to fast deceleration in an electric truck, the use of regenerative braking, instead of service brakes, sees power being put back into the battery, as well as saving brake wear.
From the driver’s seat this regenerative braking feels like the effect we have come to expect from a good engine brake or transmission retarder. The trucks slows up pretty quickly, and a lot faster than this sort of truck would expect from the exhaust brake, normally fitted with a diesel engine.
As the driver takes their foot off the accelerator regenerative braking starts. The first touch of the brakes sees the regenerative braking become more aggressive. Only further pressure on the brake pedal brings in the service brakes. The latest SEA models also use the exhaust brake stalk on the steering column to activate aggressive regenerative braking.
“We have got to try and detune the acceleration and make it a little more progressive, it might give us an extra five per cent in range,” says Joe. “It’s a culmination of different things and we are still in the research stage. We are looking at taking away the ability for the driver to become inefficient.
“Even when our vehicles go over 80km/h, the equilibrium between speed and wind resistance is quite profound on the performance of the vehicle. We are talking to customers and asking if it would be OK to limit them to 80km/h, because you could get another five to ten per cent in range.
“These are all the little things we are starting to pick up and I think we have done our analysis of this and will have something ready before April.”