The battery is one of the defining aspects of any EV (electric vehicle) and by and large it determines the weight, range, and cost of the vehicle. For these reasons an understanding of the various battery types is more than a little useful.

Types of Batteries:

While there are a lot of chemical combinations that have been made into useful batteries, in practice there are basically four rechargeable types readily available in sizes suitable for e-bikes. There are Lead Acid (PbA), Nickel Metal Hydride (NiMH), Nickel Cadmium (NiCad), and Lithium-Ion (Li-Ion) or Lithium Polymer.

   • Lead acid has been the standard for EVs for a long time. The cost is low and the chemistry well understood: charge the lead acid battery whenever you can, never leave it in a flat state, expect only 60-70% of the rated amp-hours, and be glad if you get 200 cycles in a deep discharge environment. Probably 50% of all e-bikes sold around the world still use lead acid battery packs, but their days are limited.

     As we all know, lead is extremely toxic and harmful to the environment. Some purveyors of lead-acid batteries cite the DOE statistic that 97% of the lead is being recycled. This is somewhat misleading, as the whole truth is 97% of the lead in a lead acid battery is recycled IF it’s one of the millions of batteries out there that actually makes it to a recycling facility. This is outdated battery technology and many companies still have much inventory on hand and face it, it’s inexpensive and keeps their costs down. Consider carefully for this and many other reasons, before buying an e-bike with a lead-acid battery.

   • Nickel Cadmium was the old standard for rechargeable consumer cells in the familiar AA, C, 9V series. They are known for robust characteristics, a good cycle life, and high discharge capabilities. They are still widely used in cordless power tools, R/C toys and similar applications that demand large currents, but for nearly everything else NiCad's have been replaced by Nickel Metal Hydride (NiMH) and lithium batteries.

   • Nickel Metal Hydride is quite similar to Nickel Cadmium, but with a higher energy density and a safer environmental record when disposed of in landfills. This is the dominant rechargeable battery type in digital cameras and other consumer products that offer user replaceable cells.

   • Lithium batteries power almost all consumer electronics that have a plug-in charger these days because they can store about 3 times more energy than NiMH. Lithium technology is superior because it has a number of important advantages over competing technologies (and is the only battery we use in the VoltRider™):

        1. They're generally much lighter than other types of rechargeable batteries of the same size. A typical lithium-ion battery can store 150 watt-hours of electricity in 1 kilogram of battery. A NiMH battery pack can store perhaps 100 watt-hours per kilogram, although 60 to 70 watt-hours might be more typical. A lead-acid battery can store only 25 watt-hours per kilogram and takes 6 kilograms to store the same amount of energy that a 1-kilogram lithium-ion battery can handle. That's a huge difference.

        2. They hold their charge. A lithium-ion battery pack loses only about 5 percent of its charge per month, compared to a 20 percent loss per month for NiMH batteries. For prolonged storage, best to maintain a 40% charge level.

        3. They have no memory effect, which means there is no concern of “battery memory” when applying unscheduled charges, no scheduled cycling is required to prolong the battery's life, and you do not have to (or want to) completely discharge them before recharging, as with some other battery chemistries.

        4. Lithium-ion batteries can handle hundreds of charge/discharge cycles.

        5. Lithium battery maintenance follows a simple rule: Frequent full discharges should be avoided when possible – so keep it topped up! A lithium-ion battery should provide 500 full discharge/charge cycles but may well provide 1,500 or 2,000 half cycles. So charge the battery more often, or use a larger battery, or carry the charger with you and take advantage of 'opportunistic charging'. Reducing deep discharge cycles significantly increases performance over the lifetime.

        6. A general note: heat is the enemy. Keep the lithium-ion battery cool (e.g. avoid storing in a hot car).