Ninebot ESx External Battery Adapter

This handy adapter allows you to easily wire an internal battery into the external battery port of any Ninebot ES model scooter. As described in our Ninebot Modular Battery Mount post, the cylindrical internal batteries are cheaper than the official pod shaped external batteries even though they have the same capacity. They are therefore a great option for an external battery (modular or otherwise) on a budget.

Don't own a 3D printer? Purchase a Ninebot ESx External Battery Adapter to help support our future projects.

Our early testing suggested that internal batteries couldn't be wired into the official external battery port so we simply wired our modular external batteries in parallel with the internal one. As many have pointed out, this was questionably safe due to the large voltage difference between the two batteries. Our latest tests have proven that it is in fact possible to wire an internal battery through the external battery port. The official external battery port is connected to the internal battery through 2 N channel MOSFETS allowing the speed controller to regulate the power flowing from the external battery into the internal battery. Despite this, the speed controller firmware only balances out the two batteries when they are charging. For a modular battery setup, it is therefore necessary to wire a charging plug (barrel connector) in parallel with the power leads of the external battery and plug it into the charging port of the scooter when a new battery is swapped in. The fresh external battery then begins to slowly and safely balance out its voltage with the internal one.