The Best Batteries Make The Best E-Bikes
We believe the best batteries make the best e-bikes. So what exactly makes for the best battery? Historically, ground-breaking technical advancements in batteries have come at glacially slow rates. Today’s batteries have much in common with the Sony’s first commercially available lithium ion battery released in 1991. However, even incremental improvements can still yield significant performance benefits for e-bikes. It really is just a matter of time.
One of the easiest advances for consumers to see is the increased capacity of batteries, which is measured in ampere-hours (Ah). In practice this is generally accomplished by changing the active material, which stores the lithium ions, or by engineering the construction of the battery to include more active material. Capacity translates directly to energy — measured in watt-hours (Wh) — by multiplying (Ah) by the voltage (V) of the battery pack. For a given e-bike, greater capacity (and therefore energy) equals increased riding range, like having a bigger gas tank in your ICE vehicle (you still drive, bruh?). But bigger batteries carry an increased cost and weight.
Traditionally, the 18650 cells inside e-bike battery packs have been standardized at 18 mm diameter and 65 mm long. These are the same type of cells used in everything from e-cigs and flashlights to power tools and Tesla’s. Bike brands that say they are using a “Tesla Battery” just mean they share the same cell size. They don’t have the same software or pack designs.
Another method for increasing capacity is simply to make the cells bigger. The new emerging standard are 20700 cells which are 20 mm in diameter and 70 mm in length. Karmic Bikes is fully committed to incorporating these next generation cells into our products. We see the ability to offer a battery pack that uses only 26 cells that will provide the same range as other e-bikes with batteries that contain 40 cells or more. Our total pack size will be smaller even though the individual cells are slightly larger. Additionally, fewer cells means an overall lighter weight and less chance of one cell failing and rendering the whole pack useless. This is the future of ebike technology.
So what’s next? One concern, especially with increasing the capacity of a battery, is safety. The more capacity (and, hence, energy) being stored, the larger the mess would be should something go wrong. We’ve seen this before with recalls of laptop batteries to the more recent Samsung Note 7. Significant research and resources are being poured into making batteries safer. One technology being investigated is solid state electrolytes. Currently (ha!), lithium ions are transported between the positive and negative electrodes via a liquid electrolyte and the electrodes are separated by a thin, porous, plastic membrane. Batteries fail when this membrane gets punctured and a short circuit forms between the electrodes. A solid state electrolyte would conduct the lithium ions and create a thicker physical barrier that would minimize the chances for a short circuit.
Beyond traditional lithium ion, other chemistries, such as lithium air and lithium sulfur, are also being investigated which promise greater capacity per weight and volume which would make batteries lighter and smaller. While these are many years off in terms of commercial availability, Karmic Bikes always keeps an eye out for future technologies to ensure we have the best batteries which will make the best e-bikes. Bringing them to market at the best price is a topic for another post.
-Tim
