Ninebot ESx External Battery Adapter

thingiverse

This versatile adapter lets you quickly connect an internal battery to the external battery port on any Ninebot ES model scooter. As mentioned in our [Ninebot Modular Battery Mount](https://www.thingiverse.com/thing:3702069) post, internal cylindrical batteries are more affordable than official pod-shaped external batteries despite having equal capacity. This makes them a fantastic option for an external battery (modular or otherwise) on a budget. Our initial testing revealed that internal batteries couldn't be connected to the official external battery port, so we simply wired our modular external batteries in parallel with the internal one. Many have pointed out that this was potentially hazardous due to the significant voltage difference between the two batteries. **Recent tests have shown that it is indeed possible to connect an internal battery through the external battery port.** The official external battery port is linked to the internal battery via 2 N channel MOSFETS, allowing the speed controller to regulate power flowing from the external battery into the internal battery. However, the speed controller firmware only balances out the two batteries when they are charging. For a modular battery setup, it's essential to wire a charging plug (barrel connector) in parallel with the power leads of the external battery and connect it to the charging port of the scooter whenever a new battery is swapped in. The fresh external battery then begins to gradually and safely balance its voltage with the internal one.