View source for BMS/Precharge

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[[wikipedia:Pre-charge|Precharge]] is a [[BMS]] pre-ride startup function to charge the main power bus before closing the contactor.
: The BMS has a precharge circuit for ensuring that the [[Main Contactor|contactors]] can close without causing damaging current spikes to the [[Gen2/Motor Controller|controller]] or other components.
: Precharge is necessary because of capacitors in the controller; connecting sets of capacitors electrically requires care to match voltages because of the rate at which capacitors will charge and discharge to each other to balance potentials.
: See [[Precharge Theory]] for a detailed explanation.

;Operation
* When the motorcycle is keyed on, precharge supplies a low amount of power (fused at 10A) to the controller-side main bus.
* Voltage should climb above 85V within 4-5 seconds of powering on.
* At this point, the BMS measures the voltage on both sides and decides to close the contactors.
* If this process fails, precharge will stop and then the voltage level will decay.
*: You will likely see error code 25 for a precharge error on the dash (when error codes are selected for display).

{{Warning|The precharge circuit is not isolated from the [[Gen2/Motor Controller|controller]] or [[Gen2/Accessory Charging Port|accessory charging port]], and can be damaged if a large transient current is induced from an outside source to a de-energized motorcycle.}}

;Precharge Failure
: A recent (mid-2016) firmware update improves the robustness of the precharge logic especially when used with accessory charging systems that are permanently connected to the vehicle.
:: If while starting the bike, the sequence completes before the contactor closes, the green run light for the motorcycle will flash until the contactor does close.
: To address a failed precharge on startup:
# Key the bike off if after several seconds, the contactor has not shut with an audible click and the green run light is still flashing.
# Wait 2 seconds (ensuring the dash indicator goes fully dark) and then key the bike on again.
#: This should allow precharge to get a boost from residual charge from the last precharge startup cycle.
# Repeat a few times if necessary. If the contactor never shuts, check the logs and any error codes.
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[[Category:Function]]