Battery

Robot Operation

• DO NOT plug/unplug battery while either power switch is in the on position.
• DO NOT attempt to power the robot with a discharged battery.
• DO NOT leave battery plugged into robot overnight or when not in use to prevent over accidental over discharge.

Charger Operation

LED Pattern	Meaning
Red/Green Flashing	BMS Connected; Battery Terminals Disconnected
Quick Red Flashing	Charge Cycle Beginning
Solid Red	Constant Current (SoC < 85%)
Red Flashing	Constant Voltage (SoC > 85%)
Solid Yellow	Equalize Stage
Solid Green	Charge Cycle Done/No Battery Connected

• When connecting or disconnecting the battery from the charger, ALWAYS connect/disconnect the data cable first then the power cable.
• DO NOT unplug the power cable if charger indicator is not green.
• DO NOT use any charger other than the one provided with Cassie.
• DO charge in an open and well ventilated area away from bystanders.

Battery Damage Guidelines

Battery damage includes, but is not limited to:

• Short circuit
• Drop, crush, shock, vibration, or piercing
• Temperature in excess of 60 C°
• Exposure to fire or submersion in water

If a battery begins venting or catches on fire, evacuate the area and call the fire department.

Battery fires can be extinguished using the same fire extinguisher as for a traditional combustible fire. DO NOT use a Class D extinguisher as these are meant to extinguish Lithium metal fires and will not be effective.

Best Practices

In order to prolong your battery life, please refer to the following tips.

• Depth of discharge is an important factor in the cycle life of your battery. Repeated deep cycles to 0% will negatively impact the lifetime of your pack, as will repeated shallow cycles to above 90%.
• Storing your batteries at or below room temperature will limit self discharge and increase cycle life.
• Your battery will lose charge per day from powering the battery management circuitry, so exercise caution storing batteries for extended periods. A fully discharged battery that is stored for more than a few days, or a fully charged battery stored for long periods may be unrecoverable. Battery revisions have improved the self-discharge according to the list below. The battery status checker script will indicate if the pack is first or second generation (make sure to download the newest version here
  • First generation pack (Cassie 001-003): ~4% per day, ~25 days to fully discharge
  • Second generation pack (Cassie 004-007):
• Leaving the battery plugged into the charger will not keep the battery "topped off." To charge the battery, it must be unplugged and plugged back into the charger.
  • Batteries should be unplugged from the charger when fully charged. Because of leakage current through the charger, self-discharge will increase while it remains plugged in and "shelf-life" will significantly decrease.

We recommend as best practice to have a sign out sheet for each battery you have where the state of charge and date is recorded each time a battery is used. Then when a battery is discharged below 50% it is placed on the charger, and when it has been longer than a week or so since it was used, the battery charge is checked and charged accordingly. Below are links to example policies and sign out sheets.

Battery Storage Policy

Battery Checkout Sheet