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Electric Bike Buyers Guide

Here you can find a list of item that it's really good to look at when buying the electric bike.

Content covered in the buyers guide:

1. Electric Bike Motors
2. Crank Drive Systems
3. Hub Motors
4. E-bike batteries
5. Main problems with e-bike batteries
6. Battery management systems
7. E-bike controllers

 

Electric Bike Motors & drive types


There are various types of electric bike motors available on the market. Two main types which should be distinguished are hub motors and central crank drives. There are significant differences between the hub motor and the crank drives.

Crank Drive Systems
Crank drive is located in the middle of the bike frame, just where the bottom bracket normally sits. Crank drives propel the bike through the chain with the use of the rear wheel gears. It is therefore a very efficient system because it can increase its own torque through the use of wheel’s cassette. In simple words it can allow the bicycle to climb up very steep hills. This system has a great benefits but also an associated with it drawbacks.

The main advantages of the system are the weight which is very often quite high as well as the lack of throttle. Crank drives are normally built as pedelec which only assist the rider during cycling. As a main principle the pedelec requires rider to keep pedalling by rotating the cranks. Crank drive system are also equipped with the torque sensor which identifies when rider puts higher effort on the cranks. Then higher the rider’s effort on the cranks then more power is supplied by the motor. For some people the crank drive is just excellent as it only assists during the ride. For other users it is very frustrating as it requires them to use their own power.

In conclusion the crank drive systems are very efficient and certainly a great hill climbers. They do however mainly work as a pedelecs only and require rider to put their own effort in cycling. Otherwise the motor will not be assisting the rider too much.

Hub motors
It is a completely different drive type from the crank central drive bikes. The motor is located inside the hub which propels the whole wheel independently from the bike chain or cassette. Hub motor bikes can be powered by both pedelec mode and throttle only which means no pedalling is required by the rider. It is particularly great solution for those who prefer more relaxed style of riding but also for those who love to be just assisted in a pedelec mode. With hub drives the rider can very often change the mode from throttle only to pedelec mode at any time. It can therefore suit a wider group of users.

Important to highlight is that within the hub drives there are again different types of hub motors. Some of them can be direct drive only or with the use of the internal gearing system.

Direct drive hub motors
The direct drive hub motors are very reliable and quiet. These however normally have a higher weight due to their size. The hub body is very often quite big. The direct drive motors need to be big in order to generate a sufficient amount of torque.

Geared hub motors
The geared hub motors have a different construction. The hub shell is a lot smaller and the motors weight less comparing to those with direct drive. Inside the hub the electric motor is a lot smaller but it is assisted by the internal gearing system that allows to generate higher torque. The advantages of the geared hub motors are the weight and smaller size. There are also disadvantages of this system. Normally geared motors generate some level of noise. Now those motors that use the steel gears can be really loud but those that use a Teflon gears are very quiet and the level of noise is minimal.

Conclusion
Which ones are better? Probably considering al the aspects of them the geared motors win the battle. Weight in electric bicycles is crucial and those geared motors from reputable manufacturers like 8FUN offer a great performance, reliability and low weight.

Which motor brushed or brushless?
There are also two different types of electric motors. Some of them are brushless and some are brushed. Generally we should try to avoid the brushed motors because of their lower reliability rate. Brushes need to be replaced every certain intervals whereas brushless motors can often run for years without need of any maintenance. Brushless are generally maintenance free and the failure rates on those are very low.  

 

E-bike batteries

Battery on the electric bike is just as important as the motor. Some say that is even more important then the motor as normally batteries are the ones that are more likely to go wrong. The technology in batteries in the recent years has had a huge boom. There were couple of new battery technologies introduced which continuously seemed to improve the performance of bikes.

Types of E-bike batteries
Lead acid battery - The oldest type of batteries and the worst possible choice. Approx life time of the lead acid battery is 120 recharge cycles. The batteries are difficult to recycle and also very heavy to carry. Some of the lead acid batteries have a memory effect which mean lose of battery capacity with the period of time.
Lithium Ion battery - these are a lot more advanced batteries but still not the perfect solution for the electric bike. The advantages of lithium ion batteries are the light weight construction but the life time can achieve approx 500 recharge cycles.
LiFePO4 - Lithium Iron Phosphate battery is also a lithium based mixture however with the iron cathodes. The man benefit of this type of the battery is the longest lifetime. Currently this type of batteries hasn't been used much in the electric bikes due to lower power density than the Li-Ion or Lithium Polymer batteries.
Lithium Polymer - LiMnCo02 - is the most advanced type of the batteries on the electric bikes. These batteries have the greatest power density and the super light weight construction. The life time can achieve as many as 900 recharge cycles which makes them the most popular for the electric bikes
Lithium Sulphur – This is the latest battery technology which is still tested in the laboratories. The big advantage of lithium sulphur batteries is the highest available energy density and extremely low weight. It is estimated that 360Wh battery pack might weight only 1kg. The disadvantage of this type of batteries is still a low number of recharge cycles. Currently on 250 recharge cycles is achievable.

Main problems with e-bike batteries
During purchase of an e-bike majority of buyers is not aware of problems associated with batteries. First of all it is important to highlight that the battery does not belong to the cheapest parts of the electric bike. To be perfectly honest the battery is the most expensive part of the electric bike. Currently replacement batteries on the market cost between £250 and £600 for a new battery pack. The cost of the battery varies and depends mainly on the type of this battery, bike model, its chemistry and few other factors.

The main battery problem is the loss of memory. Actually all the batteries have a memory loss and loose their capacity with the number of recharge cycles. The thing is that some batteries will barely last 6 months and they loose their 50% of capacity. The good battery can last for a period two year period and loose only 35% of it capacity.
In fact majority of good e-bike batteries should be able of doing around 500-700 recharge cycles before they need to be replaced.

Another problem of e-bike batteries is the power delivery. These days it is more common with cheap and unbranded bikes imported from China that have a very poor records of after sales service. Power delivery issue is easy to identify. The motor on the bike simply cuts off when cycling uphill. During climbing the motor normally needs a higher current in order to deliver more power. Then it drains the battery with higher current and those batteries that poorly manufactured simply can not deliver the required current for a longer period of time. It is therefore important to highlight that not every lithium battery is equal and the same. How to distinguish the good one? Those manufacturers that offer a two year warranty on the battery normally offer good quality batteries. As consumers we should however ask what is actually covered.

Battery Management Systems
BMS battery management system in lithium batteries has a role of little computer which controls the battery performance. All lithium batteries in electric bikes are built up with a number of cells which are all connected. Because of the number of cells all of them need a one central computer which controls a power delivery between cells, does the cell balancing and makes sure that the battery does not overheat and delivers the allowed current.
Again it all comes down to the price but majority of cheap lithium batteries is using a very poorly designed battery management systems. It is therefore important to ask the seller what type of battery management system is fitted into the battery. Only those branded management systems from reputable companies such as O2 Micro or Toshiba can give the best performance in power delivery.

E-bike controllers
Controller is the type of the computer which is responsible for power delivery between the battery and the motor. There are various types of controllers which can be programmed in the different way. Some controllers can be programmed as e-bikes (bike operated by twist and go only) or pedelecs (require rider’s input in order to provide assistance). Some controllers can be smarter then other as they can operate both pedelec and e-bike modes. Some controllers can also be re-programmable to run on the different set up. Some controllers also have a de-restriction options which allow to increase the maximum allowable legal speed of 15.5mph (25km/h).


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