Seth Alvo, a mountain biker and YouTube creator behind Berm Peak Express, decided to take on the status quo of big e-bike batteries. His creation, the Bermacell 14S, is a 52V battery pack for short, fun rides. Built with 14 Samsung 18650 cells, each 3,000 mAh, this battery has 156wh of power – small enough to fit in a 3D printed case that looks like an oversized 9v battery, but powerful enough to tackle trails and commutes.
Building a battery from scratch is no small task, especially for a first timer like Alvo. He sourced 14 Samsung 18650 cells, each 3.7V, and wired them in series with nickel strips and a spot welder to get 52V. A BMS was added to regulate charging, monitor temperature and make sure each cell was balanced. It wasn’t perfect – Alvo mislabeled the positive and negative terminals and his first attempts at heat shrink wrapping failed. He settled on fish paper for insulation and put the whole thing in a custom 3D printed enclosure. Despite the hiccups the final product was a sleek, functional battery, small enough to strap to a bike frame with plenty of extra strap to spare.
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Testing the Bermacell at Kanuga Bike Park in North Carolina showed its capabilities. Alvo paired it with a Bimotal e-bike conversion system on his trail bike and rode High Rocks Climb Trail, a 1.3 mile climb with 500 feet of elevation gain. In trail mode (medium power) he finished in 8:17, faster than the 20 minutes it takes on a non motorized bike. The battery was cool and full after the first lap. For the second lap he switched to Copperhead Road in boost mode and finished in 4:37. Even on the third lap he rode solely on throttle without pedaling and the Bermacell powered through, but finally hit the red zone (low voltage) after three laps, 1,500 feet of elevation.
After the bike park, Alvo tested the Bermacell’s commuting practicality. He recharged at Kanuga and rode 7.5 miles to a coffee shop, gaining 187 feet of elevation at 15.5 mph. The return trip, all throttle, pushed the battery to its limits, 12.8 miles with 332 feet of elevation gain before it died. The battery didn’t make the full 15 mile round trip but was impressive for its size. Alvo said with road tires and torque-sensing pedal assist the range could be better and it would be a great option for short commutes or quick rides.
At 156 watt-hours it’s much smaller than most e-bike batteries which are often over 500 watt-hours for longer ranges. Alvo points out a smaller battery sacrifices range but saves weight, a big deal for mountain bikers who value agility. The Bermacell’s capacity is just above the 99 watt-hour limit for air travel so Alvo plans a future version under this threshold for plane-friendly portability. The compact design opens up creative possibilities – Alvo envisions batteries shaped to fit inside bike tubes or other unconventional spaces, something larger, standardized packs can’t do.
The BMS ensures overcharging and overheating protection and the battery survived Kanuga’s steep climbs without issue. Charging was quick – Alvo charged it during his lunch break at Kanuga – but he was nervous plugging in a homemade 52-volt battery.
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