I was able to borrow some Xero 18650 3500mAh batteries for a quick test ( Capacity ) .
As delivered the resting voltage on all cells was 3.48v ( Perhaps a little on the low side )
I put all 8 batteries through my charger and they all came out ( after resting ) @ 4.15v
My initial discharge test was @ 1Amp .
With a resting voltage of 4.15v the battery voltage under load ( 1A ) quickly dropped to 3.8v and about 5 minutes latter was at 3.75v . ( Under load )
This initial discharge returned some 2779mA discharged to 3volts .. ( Not really close to 3500mA )
My second discharge was at 0.5A
This time I put the battery in a older Xtar Charger to try an top it up ( 2 batteries ) and the power supply for the charger died .
Well , I had another Xtar charger with a larger power supply so I borrowed the PS from that and topped up the batteries ..
One came of ( after resting ) at 4.19v and the other was 4.17v ..
So taking the 4.19v battery :
At 0.5A discharge the battery sagged ( under load ) to 4.02v
Discharging to 3v returned 2937mA , still quite shy of the 3500mA printed on the label .
I get the feeling the batteries are discharged to 2.5v to make the claimed capacity .. ( I will do a quick search )
From the seller :
Capacity (Ah): 3.5 Ah Max (3500 mAh) Min (3350 mAh)
Nominal Voltage (V): 3.6 ~ 3.7 V
Charging Voltage (V): 4.2 V
Charging Current (Ah): 1.47 Ah (1470 mAh)
Cut-off Voltage (V): 2.5 V
Energy (Wh): 12.5 Wh
Energy Density (Wh/L): 745 Wh/L
Max. Discharge rate ©: C Rating 2.5C (Recommended Max current 10 Amp)
Pulse current (Ah): (5-6 sec.): 15 Ah
Weight (g): 48 g (+/- 0.5 g)
Diameter (mm): 18.6 mm (+/- 0.03 mm)
Height (mm): 68.5 mm (+/- 0.3 mm)
Protected: YES (Seiko MOS-FET)
Top (positive side): Nipple top
Model: XERO 18650 GAP (NCR18650GA Cell)
Assembled for XERO PTY LTD Australia (Cell & PCB MOS-FET Made in Japan)
Yeah , 2.5v is the cut of voltage ..
A lot of devices will cut off before that ( depending on application ) , especially if safety is of concern ( RC transmitters for example ) .
Do most flashlights (1 × 18650) turn off @ 3v , probably .
These are not my batteries so my testing ends here ..
Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….