WATTS INNOVATIONS PRISM R.P.A.S., Flight Manual

Page: 133 / 141

PRISM FLIGHT MANUAL
133
In the Event of Over-Discharge of a Battery Pack (Low Voltage during flight), the pack
should be removed from duty until it can be determined if any significant damage was
inflicted to the internal cell chemistry. If the Voltage dropped below 3 V per cell under load,
irreversible damage would have occurred. The extent of this damage must be determined
before the pack can be used again.
Over Discharge will result in an abnormally warm and swollen battery pack and should be
dealt with in the following manner:
• Let the pack rest long enough for the cells to return to normal temperature.
• Connect the pack to the battery charger and log the individual cell voltages, individual
cell internal resistance and overall pack voltage.
• Charge the pack at a low c rate (0.2 C) to minimize any damage caused by the over
discharge.
• Once the charge has completed, log the individual cell voltages, individual cell internal
resistance and the total amount of charge that went into the pack.
Observations
• Observe the individual cell voltages are all similar
• Observe the Internal resistance of each cell is within acceptable level (less than 10 m
Ω
)
• Determine what percentage of the battery capacity was used
Test
• Discharge the battery through the charger at 4 amps to 3.3 V per cell under load
• The cells should measure 3.7 V each when the discharge is complete
• Calculate the percentage of total battery capacity used during the test
• The percentage used should be roughly 80% of the total capacity
• If the percentage used is higher than 90% then the pack has suffered irreversible
damage and should not be used for flight operations
10.8.3 UNSCHEDULED MAINTENANCE