About Batteries

In April 2011, we visited "Hangzhou Li'an Beyonder Power" in Hangzhou, China. This company, in operation since 2007, supplies the batteries for our Superson electric bikes. This was a very informative trip and we are grateful to "Beyonder Power" for providing some of the information that we have used in the following section. It was exciting tour the factory and take a look at some of the systems which the manufacturers have in place to make the batteries and test the performance of the batteries under stress, heat, cold, humidity and other conditions. Zeb, our six year old, also benefitted from the experiance (he was given to remote control helicopters containing Li-ion batteries also produced in the factory). It certainly made us realise that Li-ion batteries are more complex and technical than the old lead acid batteries!

Why do we use Lithium-ion batteries?

Lead-acid batteries, Nickel Metal Hydride (Ni-MH) batteries and Lithium-ion batteries have all been used as power packs in the electric vehicles. Lead-acid batteries are an older technology used less and less for E-bike applications, due to the heavy weight, large size, relatively short life of the battery and hazardous nature of the materials they contain (lead and sulfuric acid).

 

In comparison, Lithium-ion batteries are a better solution for e-bike applications, because they have a higher energy density and longer cycle life than lead acid and Ni-MH batteries, some where between 500 - 1200 charges (depending on a range of factors such as weight of the rider, riding conditions, storage conditions etc) compared to about 300 charges for a lead acid battery or 400 charges for a Ni-MH battery. The table below compares the performance of these three battery types.

 

Characteristic

Lithium

Ni-MH

Lead-acid

Working Voltage

3.7V

1.2V

2.0V

energy density (Wh/kg)

130-200

60-90

30-40

Cycle life (cycles)

500

400

300

Capacity self discharge rate (% per month)

5%

30%

10%

Memory effect

none

40%

none

Energy efficiency (C discharge/C charge )

99%

70%

75%

Weight comparison for the same capacity

1

2

4

Size comparison for the same capacity

1

1.8

3.5

Reliability

high

low

high

Source: Beyonder Power 2011

 

Types of Lithium Batteries

There are a number of different types of Lithium Ion batteries used for e-bikes, the two main types being Lithium Phosphate (LIFe-PO4) or Lithium Manganese Oxide (LiMn204). Our bikes which have either a rack mounted battery or a battery in the middle of the bike, use both these kind of batteries.

Lithium Polymer batteries, derived from Li-ion batteries are also used for some battery types (such as on our seat post mounted conversion kits). The difference between battery types is generally to do with how they are made and what they are made of. Wikipedia gives a good definition and description of each battery type for those who want more detail.

Advantages and disadvantages

Each battery type has advantages and disadvantages of a fairly technical nature, summarized below.

Lli-polymer battery cells have following advantage: they are the lightest battery available, highest energy density, no maintenance, fast charge, proven high level of stability under extreme laboratory tests, flexible shape and low self discharge. However, at the moment, being newer products, they are still relatively expensive to produce and can have issues to do with cycle degradation and charging.

Lithium manganese oxide (LiMn2O4) is used for e-bicycle applications, because of its relatively low price, safety and stability, but has the disadvantage of having reduced cycle life in high temperature. It has been in mass produce for more than 3 years, and is a relatively mature technology.

LiFePO4 has become a "best-choice" material for commercial Li-ion batteries because of its large capacity and high power for applications such as lap-top, power tools, e-bicycles and e-cars and other vehicles.

 

LiFePO4 batteries have hybrid characters: as safe as lead-acid battery and as powerful as lithium ion cells. But the consistency of the product, due in part to the relative newness of the product, and its low temperature performance can be disadvantages. It also costs more to produce than some other Li-ion types.

 

Charging the battery

Sometimes when people buy a new bike, we get a phone call saying the charger isn't working or the battery isn't charging or alike. Frequently it turns out to be user error on the part of the new bike owner. So here is some simple 'how to charge a battery' instructions!

  1. Connect the battery to the charger, ensure the output terminal of the charger and the input terminal of the battery are firmly connected.
  2. Next plug the charger into the powerpoint, the indicator LED will illuminate RED and the indicator LED will change to GREEN when the battery is fully charged. Note: if you have a 16amp (long range) battery and charger, there is an ORANGE stage between the red and green stage. The 16amp chargers also contain a fan (hence the noise).
  3. When the battery is fully charged, disconnect the charger from the powerpoint before disconnecting the charger from the battery.
  4. Your battery should now be fully charged. To check how charged your battery is, with out putting it on your bike, you can use the display on the battery itself by turning the key to the operating position and pressing the indicator button on top of the display. This display will light up showing 3 bars for fully charged etc.

Batteries we sell by type

Type Amps Use Weight
Lithium polymer small 8 smaller Volto foling bikes 2.2kg
Lithium polymer block 10 seat post mount wheel kits 2.7kg
Li-ion standard rear 10 rear rack style battery bikes and wheel kits 3.6kg
Li-ion standard 10 Standard middle type bike battery 3.8kg
Li-Mn long range 16 rack style battery long range wheel kits and Cruis-ee bike 5.7kg
Li-polymer long range 16 long range middle type bikes 5.4kg

 

Commute in a suit!

 

Looking after your battery

Information provided by the manufacturers for looking after your Li-ion battery:

Storage, maintenance and transportation

If you are not using the battery and the battery needs to be stored for an extended period, it should be kept in a dry and ventilated area and the battery should be charged a minimum of every two months. If the battery is left for long periods in a discharged state, it will permanently reduce the capacity of the battery.

The battery and charger should be kept in storage in a clean, dry and ventilated place, and should be away from excessive heat and open flames.

Optimumstorage conditions for the battery are temperatures -2035 degrees, relative humidity:565

The battery should be boxed for transport, and protected from intense physical shock, severe vibration, impact, direct rays, or water logging.

Check regulations regarding the transportation of Li-ion batteries with the airline/ courier/ carrier before transporting.

The charger should be disconnected from the battery when in storage.

Optimum storage conditions for the charger: temperature -2055 degrees , relative humidity:565RH

Operation and safety instructions - batteries

Never short circuit the discharge or charge terminals of the battery.

Never charge the battery by discharge terminals or discharge the battery by charge terminals.

Keep the battery away from fire and excessive heat. Never put the battery into a fire.

To avoid damage to the battery, never subject it to intense physical shock or severe vibration or impact.

The charger should be disconnected from the battery when the battery is not being charged.

Optimum operating temperature range when charging: 0~45 degrees

Optimum operating temperature range when discharging:-2045 degrees

Humidity while battery is in a working state:≤80% RH

Keep the battery away from children.

When the battery is not in use for an extended period of time, remove the battery from the bike for storage.

Never disassemble the battery without permission.

Operation and safety instructions - chargers

Never put anything on top of the charger.

Keep the charger away from liquids. Do not get it wet.

Never disassemble or refit the charger.

Do not use the charger in a thunderstorm.

Use only the special charger supplied by our company. Do not use another charger to charge the battery.

Never twiddle the charger or battery while charging.

Do not use the charger in an unstable, dusty or excessively damp place.

Avoid using the charger in direct sunlight.

Keep well ventilated when the charger is operating.