Understanding Electric Bike Battery Chemistry


Staff member
Hi guys! I friend on YouTube named matsv201 recently shared this great information about Lithium batteries (and some on other chemistries near the bottom) feel free to add your knowledge, I found it fascinating :)

Polymer, Cobalt-crome, Carbon and Maganese are all part of the original Lithium-Ion family and Grafine is in the experimental stage, they are similar to Carbon or Polymer, just a little bit better. They all have 3,6 or 3,7 volt and have mostly 150-250Wh/kg (for just the cells)

  • Advantages: High power, God with prismatic cells (square ones), high energy-density (typically 200Wh/kg), cheep for low capacity, fast charge (in theory), Highish efficensy (up to 95%), self contained cells (don't need a packed)
  • Disadvantages: Degrade relatively fast (about 500C in real life), not that cheep, burn really easy (quite dangerous)
  • Usage: Phones, cameras, and thin laptop computers (i can see how someone could put this in a bike to make the battery-pack really slim, but the life span would be really short
Cobalt-Crome: (run of the mill Li-Ion)
  • Advantages: Highish power, High power density (up to 250wh/kg), high efficiency (up to 98%), today one of the cheepest Li-Ion batterys)
  • Disadvantages: Degrades relatively fast (typically 600C in real life), burns easy
  • Usage: Laptop computer and power tool, i guess some E-bikes (probably some electric cars)
  • Advantages: Highish power, Highis power density (typically 180wh/kg), high efficensy, safer the the previews two.
  • Disadvantages: Degrade medium fast (like 800C in real life), a little bit more expensive
  • Usage: Electric cars, professional power tools, some compute
  • Similar to Polymer
  • Advantages: High power, high efficency, durable (3000+C), use less resources, fast charge time (10 minutes 90%), extremely safe, efficent
  • Disadvantages: Low availability, low/odd voltage (2.3V), low energy density (90wh/kg)
  • Usage: Hybrid cars mostly
  • Advantages: Almost no rare materials, theoretically cheep (but not today, probably in 5 years), durable (about 2000C), really safe, high output power, really robust
  • Disadvantages: Low availability, odd voltage (3.25V), high physical volume, slow charge time (typically 60-90 minutes), not that efficient (get warm while charging), low energy density (120wh/kg)
  • Usages: Mostly hybrid cars
  • Advantages: Cheep materials, high energy density (400Wh/kg), low self dishcharge, long shelf life
  • Disadvantages: Low power, hard to get, degrade fast (300C or so), high physical volume)
  • Usage: Science stuff
Thin film lithium (Chemically similar to standard Lithium-Ion):
  • Advantages: High energy density (300Wh/kg), low volume, fast to charge, high power, durable (10 000+C probobly)
  • Disadvantages: don´t exist outside labs, about 10-20 years to market

This is the section about non-Lithium batteries and how the different materials that were used in early generation bikes could be expected to perform.

First generation NiMh:
  • Advantages: Safe charging, needs no charging controller, safe easy to use cells, available, really high mass production, needs no packaging, can be safely used as single cells
  • Disadvantages: High self discharge, low voltage (1.25V), low efficiency (65%), really slow to charge (typically 120 minutes), actually not that cheep to make. Low energy density (80Wh/kg), not durable (500C), bad memory effect
  • Usages: single use battery replacement, older electric cars, older cellphones
Second generation NiMh (usually called ready to use):
  • Advantages: Same as the old ones, but more efficient (about 80%), faster to charge (about 60 minutes), more durable (about 600C or so)
  • Disadvantages: Lower capacity (about 70Wh/kg
  • Usages: Almost only single use replacement
  • Advantages: Safe to use, easy to use, easy to charge, cheep to make, higher power than NiMh
  • Disadvantages: Really toxic, low energy density (~50Wh), really bad memory effect.
  • Usage: industrial applications, Iligal for consumer use in Europe today
Molten salt/sodium batteries:
  • Advantages: Highish energy density (~100-200Wh/kg), safe charge, high durability, mature tech
  • Disadvantages: Low power, hot core, dangerous to handle, can´t make small batteries
  • Usage: Industrial installation for NiCd replacement, some experimental electric car.
Lead-acid battery:
  • Advantages: Mature, relativity safe charge, cheep, available, low disscharge, long shelf life (20+ years), available
  • Disadvantages: Use acid, needs services (if its not service free type) low energy density (40wh/kg typically), degrades fast (500C), toxic
  • Advantages: Really robust, higher energy density then other batteries in the family (80wh/Kg), durable (20 000C) long shelf life (15+years), really mature tech, virtually indestructible (electrically), low material costs
  • Disadvantages: Low power, hard to get, uses a pressure vessel. low voltage (1.5V), high volume
  • Usage: Space and industry
I woad say that that's all battery to keep an eye on. There is Zink and air based battery to, but they have really huge problems in the lab, and I really doubt we will ever see them in real life. Also the test results is often inflated to make this tech better then they really are, party to get funding and partly by incompetence. Regularly I see lithium-air in the tech press posted as 2000 wh/kg, that is just totally false. Its often confused because the negative side have a capacity of 600 or so Ah per kg, but both negative and positive sides is needed to make a battery. The positive side is the same as in all other batteries with 200 or so Ah per kg, making the total package probably 180 Ah or so, I would guess making a real battery around 500 or so Wh/kg, just slightly more than Li-Sulfur batteries. So basically the thin film lithium batteries will probably steamroll the the Lithium-air in 15-20 years.
Hey Court,
Thanks for posting this! One of the best concise outlines on modern battery technologies I've come across. Keep it up, loving this kind of information. It's always good to be reminded on what is possible today, next week, next year, and what is not likely possible.