Electric Bike Batteries
Batteries are electrochemical and they have their own personalities, few battery packs are identical in their behavior. 2 people can buy the same e-Bike model at the same time and have completely different experiences with their batteries. The differences between budget & well-made e-Bike batteries are significant. As an example, many of you at one point or another may have opted for a cheap generic battery over Duracell and realized that the economy is a false one for you and a waste of materials.
No matter what the lab tests say there is no replacement for the dynamic testing of end-users.
The electric bike industry has been waiting for your interest to become significant enough to allow more effective battery technologies to be offered at reasonable prices. That is starting to filter through and the following are the main pros and cons of the most frequently used battery technologies.
Sealed Lead Acid (SLA)
Pros: medium energy density, maintenance-free, tried, and tested on electric bikes, cheap.
Cons: heavy, battery cells can age quickly and die, no fast charge option, no storage option.
Nickel (NiMh & NiCd)
Pros: medium energy density, fast charge the norm, medium weight, serviceable.
Cons: Need interval discharges and servicing, suffer from memory effect, performance radically reduced in cold weather, no storage option.
If any store tells you that their e-Bike battery ‘is the latest technology’ ask them what that means. If they say ‘Lithium’ ask them which type of lithium (‘ion’ or ‘polymer’ refer to the electrolyte that holds the chemistry, not the chemistry itself so don’t accept those as answers) and what that means to the performance of the machine.
You need to discuss which Lithium chemistry suits your requirements the best, otherwise, you may not get the performance you envisage and unsuitable use of the battery may lead to a shorter life with high replacement costs.
This is where it gets really interesting from now and into the future and some basic knowledge is required for you to understand the role of the differing lithium chemistries.
Energy is released when the ions (in this case lithium-ions Li?) move from the positive anode to the negative cathode through the electrolyte. The anode is usually graphite, the electrolyte is usually a solvent-based lithium salt. The currently interesting and available chemistries are mainly focused on changes to the Cathode material which is usually a lithium-based oxide. On e-Bike batteries, you will currently see the following Cathode Oxides: Lithium Manganese LiMn2O4, Lithium Nickel Cobalt Manganese LiNiMnCoO2, Lithium Manganese Cobalt LiMnCo, Lithium Iron Phosphate LiFePo4.
The exception to the above is Lithium Sulphur Liz which uses a lithium anode and a sulfur solvent as a cathode. The potential for Lithium Sulphur is very exciting because each sulfur particle can hold 2 lithium ions compared to less than 1 ion for most other chemistries.
Pros: Very lightweight, very high energy density, durable, no maintenance, fast charge, can be stored.
Cons: Expensive, can be unstable, cells charge and discharge at different rates.
Pros: Lightest battery available, highest energy density, no maintenance, fast charge, proven high level of stability under extreme laboratory tests, flexible shape, low self-discharge, can be stored if care is taken, wide operating temperature range.
Cons: Most expensive, will suffer if incorrectly stored for a short time, can suffer thermal runaway and pose a fire hazard if charged after a period of incorrect storage or if the BMS has catastrophically failed, charging can be complicated.
Other posts in this series:
Electric bike buying guide (part 1/20)
Electric bike buying guide (part 2/20)
Electric bike buying guide (part 3/20)
Electric bike buying guide (part 4/20)
Electric bike buying guide (part 5/20)
Electric bike buying guide (part 6/20)
Electric bike buying guide (part 7/20)
Electric bike buying guide (part 8/20)
Electric bike buying guide (part 9/20)
Electric bike buying guide (part 10/20)
Electric bike buying guide (part 11/20)
Electric bike buying guide (part 12/20)
Electric bike buying guide (part 13/20)
Electric bike buying guide (part 14/20)
Electric bike buying guide (part 15/20)
Electric bike buying guide (part 16/20)
Electric bike buying guide (part 17/20)
Electric bike buying guide (part 18/20)
Electric bike buying guide (part 19/20)
Electric bike buying guide (part 20/20)