Mobile Onewheel XR/GT Hypercharger

A peak inside development of a portable XR/GT Hypercharger. It has been quite the adventure that has culminated in a polished solution for both the XR and GT ecosystems. In the process I also obtained and modified a 18S 6A AC charger (that I’ll be doing another post on) that works hand in hand with this system.

In these images we can see how I went about spot welding the pack together and installed the BMS. There were a number of battery case prototypes before I was happy with the design. The battery pack itself is a 18S1P 5Ah pack with 30A BMS, XT30 male output and has a battery gauge.

The early stages of the system utilised an XT60 for the battery to charger connection but due to the 1uF capacitance on the charger there were large sparks when connecting. As I have a lot of experience in the radio control area I ordered some anti-spark XT90 connectors without much thought on the issue. The designs were modified and the XT90 anti-spark connector was incorporated. This lasted a few connections without sparking before the incorporated pre-charge resistor burned open-circuit putting me back to sparking when connecting.

After a small amount of thought on this issue it was clear these connectors aren’t built for 75.6V(18S). 5.6ohm. (75.6/5.6)*75.6=1020.6W So even for the short time the capacitors are charging, and the pre-charge resistor is in circuit it sees over 1kW peak. For simplicity I decided on using XT30 connectors to have a discrete pre-charge circuit that is connected prior to the bypass circuit. I had some NTC inrush thyristors on hand that are 16ohm/25c so work perfect, if not over kill for the application.

This is a comparison test of the system charging a Onewheel XR compared to the standard home charger.

This is a comparison test of the system charging a Onewheel GT compared to the standard home charger.

As you probably already know, I needed to buy and cut the cable off a Onewheel GT charger for the proprietary GT connector. This is then used to charge the charge pack and a factor in making the system 18S. Charge time of the pack is just over 2h with this charger, ~0.5C rate.

To charge either of Onewheel you select the corresponding cable that alters the DCDC Chargers constant voltage output accordingly. Both are tuned to currents of 5.2A which is the same as the Onewheel GT Hypercharger constant current limit.

The last addition to this system was a wide input voltage usb supply that can supply power to USB A and/or C devices with up to 100W QC4.0 so that you can use this as a massive power bank for phones, laptops, tablets and cameras.