External Battery

[OneWheel]

Would this work with the Airwheel X8? http://www.ebay.com/itm/Portable-Power-Bank-External-Backup-Battery-For-electric-self-balancing-unicycle-/121540482737

[checho]

yes I think it will work to some degree.

However this is not the same as having 2 batteries in parallel, since it is charging the pack over the charging port which goes though the BMS, it will help extending the range of your ride.

But it will not help much to provide instant additional power for example when going up a hill, it will help a little.

For sure it will provide more than 2 Amps of current since that is the rating of most chargers, the amount of amps will be limited by the BMS of your airwheel, since it is a charging port most likely it will not go above 5 Amps, so it will help but will not provide the same number of Amps as if it was connected in parallel with the existing battery pack.

A better solution but more complicated is to connect the pack in parallel to the battery pack, but then you have to figure out how the bms is charging the batteries to protect the batteries, we do not know if the battery pack on the add has a bms or not, most likely it does not since it is not on the add. therefore you would have to figure out how to use the bikes bms with the other pack  or forget the bms in exchange of simplicity but a shorter battery life.

Having the pack in parallel with prevent voltage drops and it will help on hills, it will also keep both batteries with equal voltage.

Preventing voltage drops increases safety since it is easier for the motor to balance you, a voltage drop occurs when the batteries are partially discharge or when the motor ask for more energy like on a hill and the batteries can not supply the needed energy.

having a pack connected over the charging port it will trickle charge so it will also extend the range, however when riding fast you will be spending the energy at a faster rate than the charging port can supply so if you have a trip which many small stops it will help, but a single trip non stop you will run out of battery at a faster rate so you will end up with a discharge internal battery, and an external battery that still has plenty of charge , so you would have to wait until the batteries balance each other which could be a significant wait.