Several weeks ago, we received reports from two customers in New York that their battery packs produced smoke while installed on their 2nd generation Dual+ boards. Neither customer reported any fire or flame, injury, or property damage in either incident. We recovered both boards in person within 24 hours of each incident and began our investigation immediately. Based on our analysis, we have concluded the cause of the incidents was a short-circuit in the battery electronics. This short circuit was caused by water entering the pack due to a quality control issue in two areas of the manufacturing process.
Both batteries initially responded as designed to the short-circuit by displaying an error and disabling the board from being ridden. Shortly after, the short-circuit produced heat inside the pack, and the fire-retardant enclosure worked as designed to contain the damage.
The exterior damage to the first pack was confined to a single welt 2 cm in diameter. The second pack had a similar welt along with damage around the power button. Both packs ejected soot and smoke, but the boards were otherwise completely undamaged. In fact, both were completely rideable when new batteries were installed.
Further examination of the single recovered battery pack indicated that the cells sustained damage from the heat generated by the short-circuit. However, they remained structurally intact and did not enter a thermal runaway condition or explosively vent.
We have concluded the two quality control issues were in the manufacturing process of the water-resistant enclosure seal and the sealant applied to the electronics. These combined to allow water to enter the pack during riding and cause the short circuit. We were able to reproduce these conditions in test packs and achieve results that matched both reported incidents.
To address these, we are both improving our quality control processes as well as testing new sealing materials. This is, of course, in addition to the existing hardware and software layers of safety, onboard data logging and fault classification, and the use of fire-retardant materials and automotive-grade lithium cells.
We are now working on an updated schedule to resume shipping boards as well as a plan for our customers who already have 2nd generation boards. In the meantime, we ask that you continue not to ride or charge your 2nd generation board.
We’re thankful for every member of our incredible rider community. Have a great Thanksgiving holiday.