Battery technology is ever evolving and recent advances have allowed for some significant breakthroughs in the functionality of electric bikes. New lightweight battery designs have slashed the overall weight of the bike—but do so at a much higher price. Below is a brief overview of the primary battery chemistries used in electric bikes. This list is by no means exhaustive, but it does cover the most common configurations.

Lead Acid batteries are the oldest, and least expensive, option available. Identical to the battery in your car, these batteries are made from lead plates suspended in a wet bath of acid. Originally developed in the 1850’s, lead acid batteries are very inexpensive, but are also extremely heavy. Lead Acid batteries have the lowest energy-to-weight ratio of any electric bike battery. These batteries can be found on the lowest price-point electric bikes on the market, though the low price comes with the highest total weight of any electric bike.

Nickel Metal Hydride (NiMh) were brought to market in the late 1980’s as the first high-performance rechargeable battery. Offering a much better energy-to-weight ratio than Lead Acid, NiMh batteries became a practical solution for the large battery packs needed for electric vehicles. More recently, NiMh cells were used for the battery packs on most first generation hybrid cars—significantly driving up the cost of the raw materials that make up the battery. Advances in lithium battery technology have replaced NiMh in the majority of electric bicycles, although it is still available in some models.

Lithium Ion batteries represent the current standard in electric bikes. Packing the best available energy density into an extremely lightweight package, Lithium Ion batteries have fostered a revolution in electric bike design. Due to this new technology electric bike weights have slipped under 50lbs, all while ranges have nearly doubled. Lithium batteries are not without their pitfalls. Due to their construction, most lithium batteries are susceptible to overheating due to over-charging. To prevent this, and to ensure long-term reliability of the battery, each lithium pack should have a battery management system (BMS) installed. Some manufacturers will omit the BMS as a cost saving measure. Lithium batteries can also come in several other chemistries. One, Lithium Polymer, is a flexible cell allowing for the battery to be made in nearly any shape. The other, Lithium Iron Phosphate (LiFePo4), is a relatively new technology. LiFePo4 batteries do not have the same temperature concerns that Lithium Ion do.

The location and integration of the battery is a key feature of any electric bike. Some models hang the battery from the parcel rack, almost as an afterthought, while others mount the battery in the centerline of the frame—or even hidden inside a frame tube. Battery installation is more than just a matter of good looks. The battery represents a significant part of the bike’s weight, and its installation can affect how stable the bike is to ride.