Truck operators in the future are going to have to look at their truck charging infrastructure and work out what works best for them, and one of the decisions is about AC/DC charging for trucks.
A lot of smaller trucks, those involved in pick-up and delivery tasks, will be able to get by using simple AC chargers where batteries around 100 kWh can be charged up in around five hours or overnight. If you can get away with an AC charger for a transport task, there is an advantage, they are a substantially cheaper to buy and install than the more powerful DC chargers. If a 22kW AC charger costs $2,000 – $3,500, a 22kW DC charger will cost closer to $20,000.
As vehicles get bigger, the batteries get bigger and the operator needs higher power levels which can be provided by DC Charging systems. These DC chargers start at around 20kW, but can go as large as you need. There are 600kW DC chargers available in the Australian market if you need them.
“The current standard charging plug is called Combined Charging System 2 (CCS2), and it can handle around 350kW, so you could buy massive chargers, but you are still limited by the capacity of the plug,” says Alex Bowler, Business Development Sector Manager for bus and truck at JET Charge.
“In many instances, the vehicles have a maximum charge rate anywhere between 100kW to 250kW to protect the batteries, so you are still looking at a two or three hour charge time on some large batteries around 450 kWh. This is a long time if you don’t have a lot of downtime in your duties, but it’s more than enough for most of the bus operators we work with.”
Most DC chargers do not have batteries included in their design, they are converting the AC power from the grid into the direct current needed to recharge the battery. However, some specialist models do have integrated batteries, which are constantly being topped up from the grid, and can discharge quickly. These are useful when you have a limited electrical capacity, but still need to charge at high powers.
“The charge rate is dependent on a lot of different elements and can be constrained at a number of different points in the charging system,” says Alex. “The vehicle can constrain the charge rate to protect the batteries, or the size of the cable you are using can limit the total current.
“When using a high power charger, charge rates are generally constrained by the voltage of the battery system in the truck and the amount of current you can get through the cable between the charger and the battery. This is why its important to consider how your vehicle and charger will work together before you buy them and bring them to your depot.
“Current bus systems have around 600 to 700 volt battery architectures, and we are starting to see cars coming out with 800 volt or higher battery architectures. As the voltage goes up, you can get more power into the battery for a given current.”
New charging standards are being developed, like the megawatt charging standard, but at the moment they are all in the research and development stage. When these appear, the charging systems will be able to get much bigger and charge at faster rates.
