Ebike batteries explained? How to calculate battery range, charge and get the most out of it

Manufacturing costs of lithium battery is continually decreasing due to increased order sizes & new technology. Reports indicates that a 50% cost reduction of lithium battery manufacturing cost is feasible if high demand growth is sustained. Having said that at the moment Lithium batteries usually is one of the most expensive parts of the e-bike.  Unsurprisingly, we want to max out the battery’s lifespan as much as possible. 

The Battery Range & reality for eBike commuters

One of the main features of any e-bike you’ll find on the market is the maximum range that the e-bike can travel in a single charge. Manufacturers present figures based on their test results and do have a desire to state best case scenario most of the times.  The actual range depends on numerous factors such as power level selected, rider weight, terrain, tire pressure, weather conditions and battery state. Most people, myself included, rarely go more than 20 miles at a time without stopping (32 km). In fact, according so some recent studies done in Berlin about traveling to work, seems like half of all commuters in the city travel less than 6.2 miles (10 km).

 

cyclists

Battery Lifetime?

Like the batteries in your phone and your laptop, the capacity of the lithium batteries found in e-bikes powering the motor depreciates over time and with use. Overtime, the cells in the battery lose their ability to charge to their full capacity, and thus reduces battery performance.  You may ask but why and how? Well,  ebike battery consists of 3 main parts: Anode (the negative charge), Cathode (the positive charge) and a separator between them, normally a liquid which conducts Ions. When you charge a battery, you are forcing a whole bunch of lithium Ions into Anode (negative charge), which could be compared to absorbing water into a sponge. When you cycle your e-bike, these Ions flow from Anode (negative) to Cathode (positive), generating electric current. Over time, by stuffing the Ions in and out of the anode and cathode, you begin to damage the 'sponge', so it can't hold as many Ions, therefore the battery efficiency goes down.

On average Lithium battery technology should hold around 1000 full re-changes which is usually between 2-3 years. However, have in mind that this also depends on correct use, regular recharging & correct storage.

E-bike Battery Care – Partial Charging

There’s an old false myth that lithium batteries should be charged as rarely as possible, which is also known as partial charging.  Developing a "memory" was a problem with older nickel-cadmium (NiCad) batteries. These NiCad batteries if discharged and recharged at same state would "memorize" the charge cycle when the recharging is normally initiated and later would start suffering from student drop in voltage at that battery energy point.

In fact, that's where the whole "discharge the battery entirely” myth come from.  Exhausting lithium-ion batteries as per old myth can speed up their deterioration. Also, If the battery sits in a completely discharged state for too long, it may be difficult for it to be energised/charged. With that in mind, you can and should try to keep your battery topped up. We recommend charging after getting home or bringing your charger to work and keep a full charge before every commute, to ensure your battery charge doesn’t fall below 25% before it’ gets recharged

Ebike Battery

When you’re not on a ride, place it at dry place (between 15°C and 25°C) or in simple words – Room Temperature. Lithium-ion batteries don’t like to be stored in hot or cold environments, and prolonged exposure to moisture can inevitably ruin them too. Therefore, keep your battery indoors during cold weather and avoid storing them in direct sunlight.

 

BMS & Battery Charger

BMS stand for Battery Management System and is in every battery pack.  Truth is, Lithium batteries are relatively difficult to manage because they have a very non-linear discharging & charging curve and that’s where BMS comes into play. It continually monitors and coordinates your battery electrical current and temperature when cycling or when charging. As you may already guess, your charger and BMS has to communicate with each other due to this non-linear charging curve to safely charge and not overcharge the battery. Therefore, please use your battery charger which has been specifically designed for that battery pack and BMS.

BMS protects your battery from:

  • Over-current
  • Over-voltage (during charging)
  • Under-voltage (during discharging)
  • Over-temperature
  • Under-temperature

 

E-bike Tyre Pressure Guidelines

Your bicycle tires have rolling resistance, sometimes also called rolling friction. This is a force resisting the motion when a wheel rolls on a surface. The bigger the force the more energy will be wasted, consequently this includes the increased Wh energy per mile required from the battery. To avoid losing these precious watts, try to keep this friction to a minimum with your tyre pressure guidelines. Road tires typically require 80 to 130 psi (pounds per square inch)

As a guideline a 700 x 23c tyre on the road with a 55 kg cyclist should start with 100psi while a 90 kg cyclist should run closer to 120psi. Check the manufacturer recommended pressures for more specific guidelines. 

bicycle tyre

Measuring Battery energy and calculating battery range?

Capacity is usually measured in Amp hours (Ah) or Watt hours (Wh). They're both effectively measuring the same - Battery Energy Capacity.  For example, battery with a 5.2Ah capacity theoretically is capable of supplying 1 ampere for 5.2 hours. If you multiply 5.2 Ah x 36v (your motor voltage) you get capacity in Watt Hour (Wh), which in this example is 187 Wh.  Watt Hour is more accurate measurement of energy that Ah because it takes into consideration your motor. The range from this battery capacity energy for your bike will depend on your cycling style, terrain and weather conditions as well as motor efficiency. Varying on the ebike, your travel speed, and how electric assist mode is set, that Wh number is typically somewhere between 8 and 20 Wh per mile.  Having said that, to simplify it is considered that on average basis 12Wh is used per mile, therefore based on average cyclist or average estimates 187Wh divided by 12Wh would give you a 16mile range (25km range per charge) on average conditions.

how to calculate ebike battery range 

Disclaimer. Nothing on this site constitutes legal advice or gives rise to a solicitor/client relationship. The below information is for entertainment and educational purposes only.