Not recommended by the manufacturer. You can use these (on a budget? I get that!), but intended performance may suffer.
Battery type:18650 Rechargeable with charger
Dimensions: 6.5 cmLength x 2 cm Diameter Material: Li-ion
Charger Input Voltage: 100V~240V 50/60Hz 150mAh
Output: DC 4.2V 600mA
4 x 18650 Batteries w/Charger