Battery Management System

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Zero's Battery Management System (BMS) consists of a proprietary board within the battery case to manage the cells.

2016 BMS with potting

The same board model seems to be capable and used for both single-brick (XMX Platform) bikes and power pack (SDS Platform) bikes, given software configuration changes. The board appears to be OEM-designed and has revision numbers that indicate progression over time from the 2013 model line.

Power Note
This is the one power drain on the vehicle when it is completely turned off with no charging, but it draws a very minor amount of power like a "sleep" mode.
Warning Warning: The board is entirely solid state and not designed for fixing, only replacement.
Any damage to this board will disable the motorcycle.
Warning Warning: The board has full battery voltage inputs to it at all times.
Take extreme care to avoid connections that could short, arc, or ground.
Before accessing the BMS, first turn the bike off and disconnect charging.
This ensures that the contactor is open and you do not interact with the BMS while it performs a cel balancing operation.
Location (SDS Platform / Monolith)
Behind the lower front face of the battery behind the front forks/wheel.
Remove the lower front body plastics and the front battery face to access the unit.
Location (XMX Platform / Power Tank)
Each separate brick has its own BMS inside the armored casing.
The long brick has one BMS module inside the armored casing.
The BMS has changed layout over the years to match the monolith (particularly for long brick architecture) and increased in physical robustness and protections.
TODO identify those revisions and describe them.
The board is mounted with rubber vibration dampening.
The board is layered with a very thick coating ("dam and fill potting") to protect the components from moisture and shock damage.
The rubber pads covering reset buttons and LED indicator lights (for 2015+ models) have dielectric grease coating (CP70 datasheet) those components.
  • The covers are not there to make it waterproof, only to keep the dirt out of the grease.
  • MY13 bikes had no grease. MY14 bikes had a different grease that did not age well, and CP70 is worth applying to both MY13 and MY14.
  • Maintain that coating and do not pressure wash the front of the battery casing to avoid damaging this board.
If the BMS stops working (no indication from the lights, no response to reset), the appropriate, non-warrantee-risking thing to do is take it to a dealer and they'll likely replace it under warrantee.
But if a dealer visit is difficult or there's an emergency, a visual inspection might inform what's going on (naturally, a bike that doesn't work feels like an emergency; use your judgement).
Basically, uncover the BMS and look for burned out components.
There is a large pin connector which may be loose, which would explain a loss of power to the BMS. Apparently this is very difficult to work with but can be re-attached carefully.
Don't loosen the BMS mounting without a very good reason - it's always connected to battery cell voltage by some pins on the side that run into the batter pack so a spark there might be damaging.
If you are going to lift off the BMS, take extreme care with the fasteners and dampeners to not drop them into the battery casing.
You'll also need to restore each and every fastener and dampener because the BMS mount prevents vibration damage.
The mobile app can extract BMS logs, but it is a very slow and error-prone process compared to MBB log extraction.
The front of the board has a diagnostic port for a live debugging connection.
A cable to access the serial connection of the diagnostic port is described here

BMS Articles