This was all discussed before, as I recall the consensus was the system integrator of a DIY setup would need to label a new setup. If your setup predates the rule change it might not be required, but labeling could be applied, or it might be necessary. The easiest thing would be to label the ebike, has anyone done this? There were some basic specs for the label.
Unless they specifically say there's a retroactive application to products made before the date of the bill's activation, it might be considered unreasonable for it to affect all the products already in existence.
The label is easy for an officer to check for, while dyno'ing the motor for output power is not easy. This will likely result in a label check and no further inspection unless something really egregious happens, then they will impound and do whatever testing they wish.
Remember that the 250W systems are made primarily for other worldwide markets, and those markets often have 250W limits, so there is no factor of two in their margins (and it is common for 250W systems to exceed this by a factor of two or more during some conditions). I suspect they can be dialed to 350W in software, but beyond that they are running out of something like heat dissipation or battery maximum current so they can't get to 750W. Their torque control algorithms may also be jerky and uncomfortable or even unsafe at the 750W continuous level. At some power level a throttle is a better control input than the jerky AC input from a pedal torque sensor.
Perhaps the largest flaw in this new regulation is the Class III (28 mph) requirement to be pedal controlled, some interpret that to mean there cannot be a throttle while others interpret that to mean the throttle can only go to 20, or that the throttle only works when you are pedaling. Some of these "pedelec" bikes have a pushbutton that acts as a throttle for low speeds for walking assist or for getting going such as is convenient on a recumbent.
It is very common for an ebike to have both pedal sensors and a throttle.
This bill was driven by manufacturers wanting to sell ebikes and wanting them to have access to the bike lanes and trails so they can advertise that and sell more bikes. It was also a "legalization" of the many 28 mph ebikes they were already selling, which they generally put "for offroad use only" stickers on to keep them "legal". It is profit motivated.
Much of the propaganda that is put out about these new rules doesn't match the text of the rules, as I recall, so one really has to go to the real rules to review what is there, and they are not all that easy to interpret as DMV definitions of words are often a bit different than you expect. I should probably go back and reread them, but in fact they have had little impact except to sell more expensive high end ebikes.
Here's the text of the new bill amending the Vehicle Code: http://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=201520160AB1096
Here is the text from the above link relating to the class definitions:
312.5. (a) An “electric bicycle” is a bicycle equipped with fully operable pedals and an electric motor of less than 750 watts.
(1) A “class 1 electric bicycle,” or “low-speed pedal-assisted electric bicycle,” is a bicycle equipped with a motor that provides assistance only when the rider is pedaling, and that ceases to provide assistance when the bicycle reaches the speed of 20 miles per hour.
(2) A “class 2 electric bicycle,” or “low-speed throttle-assisted electric bicycle,” is a bicycle equipped with a motor that may be used exclusively to propel the bicycle, and that is not capable of providing assistance when the bicycle reaches the speed of 20 miles per hour.
(3) A “class 3 electric bicycle,” or “speed pedal-assisted electric bicycle,” is a bicycle equipped with a motor that provides assistance only when the rider is pedaling, and that ceases to provide assistance when the bicycle reaches the speed of 28 miles per hour, and equipped with a speedometer.
(b) A person riding an electric bicycle, as defined in this section, is subject to Article 4 (commencing with Section 21200) of Chapter 1 of Division 11.
(c) On and after January 1, 2017, manufacturers and distributors of electric bicycles shall apply a label that is permanently affixed, in a prominent location, to each electric bicycle. The label shall contain the classification number, top assisted speed, and motor wattage of the electric bicycle, and shall be printed in Arial font in at least 9-point type.
Note that it does NOT say that a class 1 or 3 ebike cannot have a throttle. It only requires pedaling for assist. So a "test for pedaling" combined with a "throttle" would apparently be legal for classes 1 and 3.
It also says After 1 Jan 2017 manufacturers and distributors of ebikes must apply a label. It says nothing about kit manufacturers or DIY builders, though it is possible and even likely that a DIY builder could be considered a manufacturer. They also specify Arial font minimum 9 point.
