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The Evolution of Electric Bike Battery Technology

Posted by Rommel Lim on

The Heart Of The E-Bike

Your battery is the heart of your electric bicycle. Over the years, the electric bike battery has undergone a lot of evolution. As early as the 1890s, electric bicycles have been documented in many U.S. patents. In December 31, 1895, Ogden Bolton Jr. was granted a patent for a battery-powered bicycle that has a 6-pole brush-and-commutator DC hub motor mounted in the rear wheel. There were no gears and its motor could get up to 100 amperes through a 10-volt battery. A couple of years afterward, in 1897, Hosea W. Libbey designed an electric bicycle that ran on a double electric motor. The motor was invented within the hub of the axle of the crankset. The design was later imitated and replicated in the late 1990s by Giant Lafree electric bicycles.

During 1898, a rear-wheel drive electric bicycle that used a driving belt on the edge of the wheel, was patented by Matthew J. Steffens. In 1899, a patent by John Schnepf showed a rear-wheel friction “roller-wheel” style drive e-bike. Schnepf’s invention was later on re-examined and improved in 1969 by G.A. Wood Jr. Wood’s invention utilized 4 fractional horsepower motors, connected through a system of gears. Late in the 1990s torque sensors and power controls were developed. Japan’s Takada Yutky submitted a patent in 1997 for a similar device. Vector Services Limited made and sold an e-bike named Zike in 1992. The bicycle had NiCd batteries that had to be built in a frame member and had an 850 g permanent magnet motor. Inspite of the Zike, in 1992 only a few commercial electric bicycles were sold.

A few of the not so expensive electric bicycles used large lead acid batteries while the newer models, in general, used NiMH, NiCd and Li-ion batteries that provided denser capacity and lighter batteries. The performance changes and in general there is an increase in speed and range of later types of batteries. Electric bicycles use rechargeable batteries, electric motors and controllers. Battery systems in use comprise of sealed-lead acid or SLA, nickel cadmium or NiCad, nickel-metal hydride or NiMH and lithium-ion polymer or Li-ion. Batteries are different depending on the voltage, total charge capacity (amp hours), weight, the number of charging cycles before degradation of performance and the ability to handle overcharged voltage conditions. The energy costs of running electric bicycles are not huge but there might be considerable costs for battery replacement. The battery pack’s lifespan depends on how it is used. Shallow recharge/discharge cycles will extend the average life of the battery.

Improvements on The Battery

The key to an electric bicycle’s usefulness is range. Range is a factor of motor efficiency, efficiency of driving electronics, design, terrain and weight of the rider and the bike and battery capacity. A few manufacturers like the American E+ and Canadian BionX provide the option of regenerative braking. The motor functions as a generator to slow down the bicycle before the brake pads engage. Some experiments use fuel cells for batteries. Other experiments involve super capacitors to add or replace batteries for cars and a few SUVs. E-bikes designed in Switzerland in the late 1980s for the Tour de Sol solar vehicle race had solar charging stations but they were later fixed on roofs and connected to feed to the electric mains. The electric bicycles were then charged through the mains just like the way it is done today. Electric bicycle batteries were made mainly by the bigger companies. Many small and medium companies however are using innovative methods to create more durable batteries. With the use of state of the art, and custom built automated precision CNC spot welding machines 18650 battery backs were made and are pretty common do-it-yourself electric bicycle makers.

New technology from Tesla has been brought to e-bike batteries. With Tesla’s advanced technology, e-bike batteries that last as long as the e-bike itself are now possible. A battery life of more than 10 years is now made realizable. Battery cell technology brings batteries capable of more pedal-supported range. The battery is expected to come out in 2018 all thanks to Tesla. Recent changes at the leading battery cell makers Panasonic, LG, Sony and Samsung has made Tesla revolutionize batteries for electric bicycles. The cells of the new e-bike batteries are like penlight batteries commonly used at home. When you connect these cylindrical shaped cells, you get an electric bike battery along with an integrated technology like the BMS or Battery Management System. The need for a new battery technology started with Tesla’s Model 3 electric car. The car needed a much extended range with smaller weight and dimensions. At first cell makers thought that adding capacity to the 18650 cells was the answer. They were able to add more capacity but it simply just was not enough. With this, the 21700 cell was born.

The Future

The 21700 battery cell was first made known to the public at Eurobike last September 2016. It was mentioned during a press release by BMZ, Europe’s biggest battery maker. BMZ boss Sven Bauer explained to Bike Europe that the new cell will revolutionize electric bicycles. The 21700 is simply a cell with a new format. Instead of a 18650 cell size, 18 mm in diameter and 65 mm height, the 21700 measures 21 mm in diameter and 70 mm in height. The bigger size provides a greater output, up to 4.8Ah. Having this capacity extends the current 500 cycles to 1500 cycles to 2000 cycles. With 2000 charging cycles, one gets a prolonged lifetime from the battery. This is very important as sales on electric bicycles, especially mountain bikes are rapidly increasing. Smaller batteries with 1500 to 2000 charging cycles with 700Wh are going to be the new standard in 2018 according to GM Mo-Hua Yang of Taiwan-based battery maker HiTech Energy.

The evolution of electric bike batteries has really come a long way since the late 1800s. Electric bicycle batteries have changed with electric bicycles and with the needs of electric bicycle rides. Who knows what the future might bring for this simple but amazing technology.

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