From Unofficial Zero Manual
This describes any riding situation where the relationship between throttle input and power is diminished.
- The rate of power onset with throttle input is reduced.
- The limit of power at full throttle twist is reduced.
- Potential Causes
- The direct cause is typically current limiting by the MBB and/or controller.
- Low battery voltages at low SoC can trigger current limiting.
- Power (kW) = Current (A) × Voltage (V)
- So, a given power demand will require more current at low voltage than at higher voltages.
- The MBB and/or controller typically impose current limits on the main power bus for performance models (SR, DSR, FX, and FXS) at SoC below roughly 40%.
- Very low voltages (below 96V?) will trigger significant power reductions.
- Cold battery temperatures can trigger current limiting, since internal resistance rises at low internal temperatures.
- High battery temperatures can trigger current limiting directly.
- The MBB will limit current to reduce internal heating of the battery.
- Often, very hot ambient temperatures can reduce the battery's ability to cool itself while riding, which makes this condition easier to trigger.
- Potential Solutions
- For low battery voltages, charge the bike to get more/full power.
- For low battery temperatures, riding at slow speed while monitoring battery temperature can raise its temperature until the condition clears.
- For high battery temperatures, successive year builds of the battery typically offer lower lower internal resistance.
- Basically, a newer bike will be more robust against current limiting conditions by not heating up as readily.
- From EMF:
- ... higher internal resistance of the battery at colder temperatures causing current limiting, ... It can be a little disconcerting when this happens right as I am trying to overtake slower vehicles.
- You can even see that in the logs.
- You'll see entries
discharge current limited (XX%).
- That tells you the percentage the power (=battery current) has been limited to, because of the high voltage sag due to higher internal resistance because of the cold.
- Right behind that you will read a
- this one tells you which cell was the weakest and caused the limitation and with what voltage.
- The limitation of power is directly related to topspeed, as you need more power the faster you ride.