What kind of batteries do electric bikes use?
Electric bikes use three major battery types, Lead acid, NiMH, and Lithium Ion. The Lithium Ion batteries are significantly lighter than the other two types and last 50-100% longer. For this reason we only deal with bikes and kits that use a Lithium Ion type of battery. The types of Lithium batteries that we use on electric bikes are listed below:
Lithium Polymer
The lithium polymer (LiPoly) battery is definitely the lightest battery option available, making them evermore popular on ebikes and RC planes and helicopters. The LiPoly cells can handle very high discharge currents which works well in these applications. The LiPoly batteries that we supply are contained in rigid enclosures, making them structurally sound to avoid damage. LiPoly batteries traditionally had some bad reviews a few years ago with them being volatile to punctures, creating a fire. This however, has been eliminated in the newer generation of batteries that we carry and are able to withstand punctures and overcharging without the chance of flames. Pretty good advancements for a battery that’s only been on the market since 2006.
Lithium Manganese
Many quality electric bike and kit manufacturers have been using the Lithium Manganese (LiMn) batteries since 2005. They are heavier than the polymer batteries but seem to perform quite well. They have good discharge capabilities holding voltage better over the course of the battery discharge than the Lithium Polymer. This means that the Manganese battery holds its power right until the end of the batteries discharge, while the Polymer has less power towards the end of it’s discharge. We have however, found that in real world conditions (especially Canada), that the LiMn are not lasting as long in lifespan as we would have hoped. This may attributed to the BMS (battery management system) that controls the output of the batteries. If one of these cells fails prematurely, the entire pack is negatively affected. Companys like BionX use a LiMn pack that does not have a BMS and does not have the same failure rate. We have also found that moisture can affect the LiMn packs more so than the Polymer and the Iron Phosphate packs.
Lithium Iron Phosphate
The lithium iron phosphate (LiFePO4) battery is by far the most discussed battery of 2010. Many companies including Black & Decker’s DeWalt brand, GM’s Chevy Volt and others are using the LiFePO4 batteries made by the manufacture A123 Systems. Samsung has released their own mass line of iron phosphate batteries, which are available through the eZeebike line of electric bikes. Most manufacturers are claiming 1500 to 2000 cycles out of a battery, almost double the LiPoly batteries. The LiFePO4 batteries are about as heavy as the manganese batteries and do cost about 15-20% more than the polymers but are probably the most economical in the long run. We hope to see what another year of testing and design will bring us.
Batteries have been the hurdle that electric vehicle enthusiasts have been working on since the first electric bike and car were produced in the 1890′s. We feel that in the last ten years, the amount of human ingenuity and persistence in the area of battery technology has made the electric dream a very feasible reality. There has never been a better time to be involved with such an interesting and sustainable mode of transportation.