Some thoughts on 2016 and later .. namely when does Zero switch to a high voltage system.
Two engineers at Zero recently have given interviews where they've strongly indicated they're not looking at high voltage systems.
The first is an interview with
Abe Askenazi, Zero's CTO.
Most powersports equipment is based around Field-Effect Transistor (FET) technology, which peaks around 130 volts. When you go to higher voltage, you have to go to Insulated-Gate Bipolar Transistor (IGBT) technology. The car guys are at 300-400 volts, which incidentally the Harley-Davidson Livewire is 300 volts. But at the level of power that a motorcycle makes, the difference is not that impactful. It’s also a safety issue: Our manufacturing is pretty high-end, but we don’t have automotive levels of safety, and we can’t guarantee that every dealership is going to have high-voltage safety systems in place. The standard for powersports and industrial equipment such as forklifts is 102 volts, which if you screw up will shock and hurt you, but isn’t fatal. If you get shocked with a 300-400-volt battery, you’re dead.
The second are interviews Luke Workman has conducted with both
Motorcycle.com and
gizmag, during a Zero factory tour. Note the same photos supplied with both articles. Luke is better known in the EV community as liveforphysics.
So why not go up to a higher voltage that would work with the existing charging infrastructure? "If we went to 300 volts, it would hurt you on every front that matters," says Zero's Senior Battery Specialist Luke Workman. "We'd have lower efficiency, lower power, higher cost, higher drive train heat – and in terms of life safety for the guys that are working on these things, you go from a nasty tickle … to dead. The majority of electric vehicles that are using higher voltages are doing so simply because they've been designed using legacy equipment. You'll see a lot more EVs going low voltage in the future."
So why do we want high voltage anyway? Two things: higher power motor controllers and DC quick charging.
1. Higher power motor controllers
The Zero SR and Brammo Empulse use the Sevcon Gen 4 Size 6, one of the largest "low voltage" motor controllers. They're pretty quick! But there's always someone who wants more power .. like Luke. For larger bikes or regearing for higher speeds, both of these applications will need more power, as well as better cooling.
For more power, the answer traditionally has been to go higher voltage. Energica, Mission, Lightning, Brammo's RR bikes all use these ~350V high power motor controllers. Sevcon, Curtis, and Kelly all top out at around 50 kW with their ~100V AC motor controllers. Zero seems to have more clout with suppliers nowadays; can Zero convince Sevcon to build a larger low-voltage Gen 4? Or use two smaller motor controllers? Or maybe someone - Zero in-house? - will build a higher power low voltage controller?
2. DC quick charging
Presently Zero's bikes are ~100V and 110 Ah for the ZF12.5, or 135 Ah for the Power Tank model. In order to get a 30 minute 80% charge on Zero's present bikes, Zero will need about 200A DC. For a larger bike - suppose they built a six or eight brick pack at the same voltage - they would need 300 to 400A DC to get the same 30 minute 80% charge.
CHAdeMO presently supports only up to 125A, though the spec supposedly
can be extended up to 200A. SAE CCS supports up to 200A already, and may be able to be extended up to 400A. Existing chargers may not support voltages this low or currents this high. And - after the short-lived CHAdeMO adapter for the 2013 bikes - they need to make sure DC charging is bulletproof and works every time, all the time.
In the meanwhile, Zero is taking an active role in trying to push adherence to fast charging standards. "We're on the committee for the IEEE P2030.1 DC fast charging standard," says Zero's Head of Electrical Engineering Kenyon Kluge. "Our goal is simply to push for compliance with the spec that already exists."
This is a long-term play on Zero's part IMO. Any steering pressure Zero can apply as part of the IEEE committee (which I believe has some input into both the SAE and CHAdeMO charging standards groups) will take years to resolve .. and in those years, perhaps the old incompatible chargers will be taken out of service, and the charging networks will grow to a point where DC QC travel is realistic.
