Riding Data & Regen

Understanding Current Flow

The current fields (BattAmps, MotAmps, I) tell you what the bike is doing. The sign and context determine the state:

The motor those amps are going into

Every current, temperature and RPM channel on this page is a measurement of one machine: a Z-Force motor bolted to the frame, fed three-phase alternating current by a controller, driving the rear wheel through a single belt reduction. Nothing about that layout changed between 2015 and 2026. What changed is the size of the motor, the rotor inside it and the amount of current the controller is allowed to push — and every one of those changes shows up in the log before it shows up anywhere else.

Zero names its motors by a two-number designation: a nominal stack diameter of 75, then a length. Across the 117 model-year specification rows in our manual index there are 6 of them, and the pattern is simple — a longer stack is a bigger motor. Every one of those 117 rows describes the motor as passively air-cooled in Zero's own words, and not one describes anything else. There is no pump, no radiator and no fan on the motor of any Zero in this table, which is the single most important fact for reading a MotTemp trace: the only thing carrying heat away is the case, the air moving over it and time.

The rotor changed in 2016, and Zero wrote it down in one word

The community archive states that Zero moved from a surface-magnet rotor to an interior-magnet rotor for 2016, that the interior design produces less heat for a given output and spreads what it does produce more evenly, and that the changeover was not clean: some models kept the older rotor through the model year. That is a substantial technical claim with no citation on the page. It is also correct, and Zero's own manuals prove it in a single word.

Zero never writes “IPM” or “surface magnet”. It writes a Magnet Configuration line, and in 2015 and earlier that line reads radial flux permanent. From 2016 onwards the same line on most models reads radial flux interior permanent. One inserted word, in 62 statements across the index, dates the change precisely — and the 2016 manuals are the interesting ones, because they print both.

What the motor cannot tell you about itself

Two things a rider reasonably wants are simply not in any manual. There is no published maximum motor speed for any Zero — searching the full text of all 36 in-scope owner manuals for an RPM limit returns nothing at all. And there is no published temperature at which the motor derates, only the behaviour it produces, which the derating section below sets out. The archive fills the first gap with a figure of 6,000 rpm and an argument about winding inductance rather than a measurement; the final-drive section takes that figure apart using Zero's own gearing.

The motor also has to be told where its own rotor is. Both the encoder and the controller hold a calibrated offset angle, and Zero treats that calibration as a serviceable item rather than a factory setting: the owner-manual maintenance schedule lists Drive Motor — commissioning and timing as a periodic check, and the service manuals route it through the dealer Diag4 software with the motorcycle on a stand and the rear wheel spinning under its own power. The FST procedure adds a tolerance that tells you how tight the setting is: if the newly measured offset differs from the stored one by more than five degrees, the manual says do not return the motorcycle to service. A motor that has been unbolted and refitted without that step is not finished, whatever the belt tension says.

The controller, and the number that really caps MotAmps

The motor controller is the only thing on the motorcycle that decides how much current reaches the motor. It takes direct current from the pack across two terminals, switches it into three alternating phases across three more, and holds the phase current to a ceiling written into its own configuration. When you see a MotAmps trace flatten off at the same value ride after ride, that ceiling is what you are looking at — and Zero publishes it, in amps, on the specification page of every owner manual it has ever printed.

Reading it out of all 36 in-scope owner manuals gives 103 controller lines and 10 distinct ratings between 420 A and 900 A. Grouped by platform, they form a ladder that maps exactly onto the hardware changes riders already know about.

Gen2 is a Sevcon. Gen3 is not, and Zero says so by omission

On the S, DS, SR, DSR, FX, FXS and FXE the controller is a Sevcon. Zero does not advertise that in the specification chapter, but it says it twice elsewhere. The diagnostic trouble code list in 22 manuals contains three codes named after the supplier — 31 Sevcon CAN Error, 33 Sevcon Error Turn Off, 48 Sevcon Startup Disable — and the Motor Controller Replacement procedure in the S-platform service manual is written in two variants, headed Size 4: and Size 6:, which is Sevcon's own size nomenclature for the Gen4 family. The archive's controller table asserts exactly that mapping, uncited.

The MY2017 step in that ladder is the one worth pausing on, because three independent specification fields move in the same model year. The phase current rises on both variants. The final drive changes belt family and sprocket counts, as the final-drive section below shows. And the archive records, separately, that the motor shaft went from keyed to splined at the same point, which is why a 2016 motor and a 2017 sprocket do not fit each other. We can confirm the splines exist — the FST service manual has you inspect the motor shaft splines for damage — but no manual in our index documents the changeover itself, so the date remains a community claim on a page that has been right about everything else we could test.

On the SR/F, SR/S and DSR/X there is no Sevcon. Not “a different Sevcon”: across every FST manual in the index the string appears zero times, the Sevcon-named fault codes are gone, and the fault list is renumbered into a different vocabulary entirely. Meanwhile the Sevcon codes are still in the FX and FXE manual as late as MY2025. The two architectures ran side by side for years, which is why a single “what controller does a Zero have” answer is always wrong.

From 2024 the ceiling is a firmware setting, and Zero prints both numbers

The clearest evidence that the phase-current ceiling is configuration rather than hardware arrives in the MY2024 manuals. The same motorcycle, with the same motor, is specified twice — once for each licence category it can be sold under — and the two specifications differ in the controller line. Zero even uses the word: firmware-limited.

How the controller gets rid of its own heat

CtrlTemp is not measuring air. On the Gen2 platforms the controller is bolted to a separate finned heat sink with thermal compound between the two faces, and the service manual is emphatic about it: a layer of thermal grease must be applied, spread with a small roller, and the manual describes the correct thickness by appearance — white, but with the grey of the metal still showing through. Too little leaves gaps; too much stops the joint closing when the bolts are tightened. Either way the controller runs hotter for the same current, and the only place that shows up is CtrlTemp climbing faster than it used to on a ride you have done a hundred times.

On the FST platform the split disappears. Up to MY2021 the controller sits on a carrier; from MY2022 the service manual's section is titled Motor Controller with Heatsink and the mounting torque changes with it. The five power terminals stay five throughout, on both architectures — two for the pack and three for the motor phases — which is why the FST power-pack procedure, which comes out past the controller, calls for five new controller cable seals and five new O-rings.

Look up your own machine

The answer to “what is in mine” depends on the model, the model year and, from MY2024, the licence category the bike was sold under. Rather than print 117 rows, this reads the same generated index the tables above use.

Regenerative Braking

Regenerative braking is one of the key efficiency advantages of electric vehicles. When you release the throttle or apply brakes, the motor becomes a generator:

Temperature Management

Heat is the enemy of battery life and component longevity. Your logs track multiple temperature points to ensure everything stays within safe limits:

What derates, and how the log shows it

“Derating” on a Zero is not a fault and not a single mechanism. It is a thermal strategy that reduces available power so that a passively cooled powertrain can keep running, and Zero describes it in the same words in every manual from MY2014 to MY2026: the powertrain cannot be operated indefinitely at high power and high rpm without reaching its thermal limitations, so the motorcycle reduces speed and power until it reaches a state it can sustain. The FST manuals add, pointedly, that the indicator coming on does not mean anything is malfunctioning — it means the strategy is working.

What the manuals do not give is a threshold. There is no temperature in any of them at which derating begins. What they give instead is something better and almost universally overlooked: a second top speed. Every Zero specification page prints an estimated top speed (max) and an estimated top speed (sustained), and the gap between them is the manufacturer's own statement of how much the thermal strategy takes away. It appears on 59 of our specification rows, across 7 models.

Retracted: this page used to say Zero publishes no numeric motor temperature

Those bands change how the archive's motor table reads. It puts “normal” at up to 100 °C. Zero's own dash still shows white — its unremarkable colour — up to 118 °C, which is 18 °C higher, and does not go red until 118 °C. A rider using the archive table would conclude their motor was in trouble at a temperature Zero considers ordinary.

Two fault vocabularies for the same two components

Zero does name the stages — it just never numbers the temperatures. The Gen1 and Gen2 diagnostic trouble code list carries four powertrain-thermal codes, two for the motor and two for the controller, each split into Stage 1 and Stage 2. That is where the archive's column headings come from: the vocabulary is Zero's, the numbers are the community's. On the FST platform the list is renumbered and the stages collapse into single codes whose description is the action rather than the severity.

The final drive, and the speed nobody measures

There is no gearbox. Every Zero in this reference is specified as Clutchless Direct Drive: the motor shaft carries a toothed pulley, a single toothed belt runs back to a much larger sprocket on the rear wheel, and that one reduction is the entire transmission. It has two consequences for the log. Motor speed and wheel speed are locked in a fixed ratio, so MotRPM is a proxy for road speed with no gear to guess at. And the belt is the only mechanical component between the motor's torque and the road, which is why belt tension appears in the maintenance schedule at the same interval as safety items.

That MY2017 row is the same model year the controller current rose and, per the archive, the motor shaft went splined. Three specification fields and one community claim all point at a single drivetrain revision rather than three coincidences — which is a useful thing to know before assuming a part from a 2016 bike fits a 2017 one. Belt tension, alignment and wear are their own subject and have their own page: the drive belt reference covers the tension bands by model year, including the ones our own spec data used to get wrong.

What the gearing says about motor speed

No manual gives a maximum motor speed. But a fixed reduction, a sprocket count and a tyre size are enough to work it out from the top speed Zero does publish, and doing that across 70 model years is the only way we have of testing the archive's 6,000 rpm ceiling.

Across 31 Gen2 model years the answer lands between 5,187 and 6,330 rpm, which brackets the archive's figure closely enough that it is very probably a real number for the machine it was written about. The SR/F and SR/S do not fit it: their gearing and their 200 km/h (≈124 mph) maximum imply about 7,581 rpm, roughly 26% past it. So the ceiling is not wrong so much as dated: it describes the Sevcon-era motor, and the archive page it sits on was last edited before the SR/F reached customers. Repeating it as a fact about a modern Zero is the error, not the number itself.

Motor alignment is not two steps

The motor is not simply bolted to the frame. Its rear face carries jack screws that set its position relative to the swingarm pivot, and that position is what keeps the belt tracking straight. The archive documents the adjustment in two lines — loosen four screws, turn the silver nut — and both lines are true. They are also nowhere near the whole job.

Typical Efficiency by Model

These figures are not community folklore — they are computed from Zero's own numbers. Every row is nominal pack kWh × 1000 ÷ rated range km, taken straight from the model-year spec sheets in the owner manuals. Zero's “city” range is the EPA UDDS cycle; “highway” is its sustained high-speed figure. Where a model spans several manual years the spread is shown.

Key Riding Log Fields

These are the Gen1/Gen2 MBB field names — the S, SR, DS, DSR, FX, FXS and FXE. They also survive on the 538XX firmware variant, which decodes pack voltage, battery current, SOC, RPM, temperatures and a real odometer. Read the caveat under the table before you go looking for them in a Gen3 file.