18650B Built-in Micro USB Rechargeable Lithium-Ion Battery. 3.6V - 3500mAh Charge. Win. Repeat. The SF18650B is a Lithium Ion-protected 18650 battery with MICRO-USB charge capability. This allows the user to conveniently charge the battery using any USB power source such as a USB wall charger, computer/laptop, power bank, or automotive USB port using the included MICRO-USB to USB cable. PRC