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Phoenix Rising
Phoenix Electric SUT
By Tom Bartley. The rumors of the demise of Phoenix Motorcars have been greatly exaggerated. Plagued by early orders that weren’t really there, battery pack performance problems, and traction motor inverter/controller hiccups, Phoenix Motorcars was down but, indeed, is rising once again. The current business plan calls for 200 vehicles to be delivered into demonstration projects to show the operational feasibility of an all electric Sport Utility Truck (SUT). During a recent visit to their Ontario, California facilities I got an inside look at a company poised to do business. I didn’t count the exact number of SUTs parked around the lot and inside the buildings, but 200 seems like a pretty good estimate. If you remember this SUT was touted for high speed highway travel fully loaded with a range of over 100 miles. Hooray for another electric vehicle that offers real performance to alter the generally accepted golf cart public image of electric vehicles!
The large volume order of 100 kW UQM electric traction motors made headlines when it was canceled. Phoenix has a new supplier for a less expensive higher power 125 kW electric traction motor with matching inverter/controller. The energy storage pack is still based on lithium titanate battery chemistry, but now they have three different cell suppliers (perhaps Altairnano, Mitsubishi and Kokum) and do their own “pack” design and assembly.
The Battery Pack
Altairnano promotes the quick charge capability, safety, and wide temperature of operation as the advantages of this particular lithium ion battery technology. The military shot holes in it to verify its safety and the thermal runaway temperature has been pushed up to over 240°. Phoenix talks about a 10 minute full quick charge in addition to the other charging modes. The energy density matches today’s nickel metal hydride packs, somewhat less than other li-ion chemistries, but something had to give.
The flat prismatic cells are grouped together in modules that are structurally supported, but otherwise open to the air for maximum cooling effect. The flat metal electric interconnects offer low inductance and minimal resistance, something really important for the extremely high current quick charge. The whole assembly is nicely designed to fit in a composite “tub” that conforms to the space in between the frame rails just ahead of the rear axle traction motor.
Manufacturing Production
Some serious manufacturing thought went into the production assembly procedure. The vehicles arrive as gliders without engines or transmissions from an Asian supplier. Each SUT glider sits on a roll around cradle while the wheels are removed and the dashboard is removed for access to the required modifications to prepare the car for the battery and electric drive system. The battery pack mounts between the frame rails just ahead of the inverter/controller and traction motor that drives the rear differential. Reportedly, one person can complete an entire assembly in 32 hours. A front wheel drive option was considered, but rejected when the component and assembly costs started to rise.
Fast Charge Energy Loss
A note about efficiency and quick charging: A full 50 kWh charge in 10 minutes requires a 300kW power source, something that may be hard to come by without a very expensive power supply and an agreement from the local power company. One option is to slowly charge a separate battery pack that can dump its energy into the vehicle pack in 10 minutes. Here is my concern: the round trip energy efficiency of a good battery is 85%. For two batteries it drops to 72%. If I add the resistance of the conductors, connectors, and switches inside each pack, the resulting efficiency is probably close to 50%, where half the energy is thrown away as heat. Speaking of heat, with charging currents over 400 amps during a quick charge, it is like having over 100 hair dryers generating heat inside each pack. Getting rid of that much heat without causing premature aging of the cells and electrical connections is a real challenge. My congratulations to the battery management system if it can really do it. Otherwise it would be wise to plan normal operations for middle of the night slow low energy rate charging.
Adjustable Braking Energy Regeneration
One nice control feature is a driver selectable level of braking regeneration. Normally, for maximum efficiency in recovering braking energy and saving brake pads, full regeneration is applied upon releasing the accelerator at the highest speeds. However, it seems this is a problem in stop-and-go highway congestion because the deceleration occurs too quickly and the accelerator has to be reapplied to maintain the vehicle position in the stream of traffic, thus defeating the energy recycle savings. The driver selectable level of braking regeneration lets the driver select a deceleration to fit the traffic conditions.
Return Trip
I hope to return to Phoenix next month for a test drive. I’ll report on the “feel” of the control system.
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