Specifications

Part number: B420 YS1550-3S-XS

Discharge connector: XT60

Balance connector: 4-pin JST-XH

Rated parameters
Dimensions	20 x 45 x 90mm
Continuous Discharge	108.5A
Capacity	1550mAh
Nominal Voltage	11.1V
Charge	1-3C
Weight	165g

Derived parameters
Energy Capacity	17.21Wh
Energy Density	375.4J/g

Observed parameters
Dimensions	21 x 43 x 92 mm
DC Internal Resistance	~8mΩ
Capacity	~1400mAh

Photos

From the manufacturer:

Test Results

Continuous discharge:

Vaping profiles:

Test results yield an average of 1400mAh per pack. Accordingly, I assert that these packs are roughly 10% over-rated with respect to capacity.

Observations

The packs tested heated to ~29°C and swelled visibly after a minute at 10A constant discharge.