Seth Alvo, a mountain biker and YouTube creator behind Berm Peak Express, challenged conventional e-bike battery design with the Bermacell 14S. This 52V battery pack is made for short, fun rides. Using 14 Samsung 18650 cells rated at 3,000 mAh each, the battery delivers 156Wh of power. It’s compact enough to fit inside a 3D-printed case resembling an oversized 9V battery, yet powerful enough for trails and commutes.
Constructing the battery from scratch was a learning experience for Alvo. He wired the 14 Samsung 18650 cells in series using nickel strips and a spot welder to reach 52V. A BMS was added to manage charging, monitor temperature, and balance the cells. There were some early missteps—he initially mislabeled the positive and negative terminals and struggled with heat shrink wrapping—but he eventually used fish paper for insulation and housed the battery in a custom 3D-printed enclosure. The final product is sleek, functional, and easily secured to a bike frame with plenty of strap length remaining.
Testing at Kanuga Bike Park in North Carolina demonstrated the Bermacell’s performance. Paired with a Bimotal e-bike conversion system on his trail bike, Alvo tackled the High Rocks Climb Trail, a 1.3-mile ascent with 500 feet of elevation gain. Using medium power, he completed the climb in 8:17, compared to the 20 minutes it would take on a non-motorized bike. On a second lap up Copperhead Road in boost mode, he finished in 4:37. Even on a third lap powered solely by throttle, the battery performed until finally reaching low voltage after three laps and 1,500 feet of elevation.
Alvo also tested the battery for commuting. After recharging at Kanuga, he rode 7.5 miles to a coffee shop, gaining 187 feet in elevation at an average of 15.5 mph. On the return trip using only throttle, the battery lasted 12.8 miles with 332 feet of elevation before running out. While it didn’t complete the full 15-mile round trip, the Bermacell’s performance is impressive given its size. With road tires and torque-sensing pedal assist, the range could be improved, making it a practical choice for short commutes or quick rides.
At 156Wh, the Bermacell is much smaller than typical e-bike batteries, which often exceed 500Wh for longer ranges. Alvo notes that smaller batteries trade range for reduced weight—a major advantage for mountain bikers prioritizing agility. Its capacity is just over the 99Wh limit for air travel, so Alvo plans a future version that complies with airline restrictions. The compact design also allows creative placement options, such as inside bike tubes or other unconventional spaces, which large standard packs cannot accommodate.
The BMS protects against overcharging and overheating, and the battery handled steep climbs at Kanuga without issues. Charging was quick enough to do during a lunch break, though Alvo admitted some nervousness about plugging in a homemade 52V battery.
