How to choose a battery for an electric bike conversion kit ?

The battery is the heart of your electric bike kit. That why it is the most expensive component of the kit.

Contrarily to a lead battery, a lithium battery is a complex product which requires thinking before purchasing.

You will find in the following paragraphs, the basic information to select the battery which corresponds to your needs and to differentiate a “good” battery from a “bad” battery.

Several elements matter during the selection of battery for an electric bike conversion kit. The most important criteria are :

  • budget
  • kit power
  • autonomy needed
  • geometry of the bike frame and battery positioning
  • weight limitations

 

The budget :

As you know, a lithium battery has a high price range. The price of a lithium battery depends on the quality of its cells and on the BMS which compose it, but also on its capacity and voltage.

With an equal cells quality, battery price will be proportional to its capacity : A 15Ah battery costs around 50% more than a 10Ah battery.

More the voltage increase, more the constitutive elements of the battery increase. A battery 48V 10Ah will be more expensive than a 36V 10Ah battery.

So you have to define your needs in power (choice of the quality of the cells), in maximum speed (voltage choice), and in autonomy (capacity choice).

 

The power of your kit :

To give the possibility to anyone to get a conversion kit, we offer several batteries technologies, qualities, voltages and capacities.

During the choice of your battery, please have a look at the technical product specifications especially at the continuous discharge intensity available.

If for example, we take a bottle battery 36V 9Ah, its continuous discharge intensity is 15A, which means that the battery cannot be used on electric kits of more than 400W.

Please follow our preconisation on battery choice at the bottom of each kit page.

 

The autonomy you need :

On that matter, we invite you to read the corresponding chapter by clicking on the following link : estimation of the autonomy of your electric bike conversion kit.

 

Geometry and positioning of the battery :

We offer several geometrical formats of batteries adapted to every bikes and uses.

For a city bike, batteries with a double bicycle rack are interesting because the battery can be locked on the lower rack, leaving the upper rack available for a basket or a baby seat. This solution is also interesting for front wheel motorizations in order to get a better balance of the weights.

For bicycles with a triangular frame (Mountain bikes, hybrid bikes, road bikes) used on roads and forest roads, the position of the battery on the bike frame will import to reach a better balance on the bike.

For mountain bikes used on specific courses (trail, bike park…) we advise you to place your battery in an EVOC backpack with a dorsal protection EC certified. This solution will allow you to protect your battery in the case of a fall and to protect it from vibrations in order to keep a light and movable bike.

 

Frequently asked questions :

 

What are the differences between a 36V battery and a 48V battery?

More the voltage of your battery increase, more your motor will work faster.

On a same motor, using 36V then 48V generate maximum speed rise of 5 to 10 km/h and increase the available torque by 10 to 15% depending on the motor.

Is a 48V 20Ah battery more powerful than a 48V 10Ah battery?

In average an electric bike need that a battery able to handle discharge current between 20A and 30A.
As you can see in our “battery” offer, some of our 10Ah pack accept 20Ah max whereas other accept 40Ah max.
This is directly linked to the quality of the cells.
 
However, when we take two entry level range of packs, each supporting 20Ah max (15Ah continuously) and by linking them in parallel, the new 48V 20Ah pack built this way will accept a discharge intensity of 40A max (30A continuously).
It is this technique that some sellers use offering 48V 20Ah batteries at a very appealing price and accepting high discharge intensity even is the cells are low quality cells.
This type of installation in parallel has a harmful effect producing the quick aging process of the cells, there will be an energy transfer from the most charged cells to less charged, so it results in a contamination of the “good” cells and a premature aging of your battery.
 
Be careful with this type of products for which effectiveness in the long run is not as good as it seems. .
 
We advise you to take two 48V 10Ah batteries of a good quality instead of a 20Ah offering you the results but with lower quality cells.
Another advantage of this solution is that you can take only one battery for short trips instead of always transporting a heavier 20Ah battery.
The capacity is directly proportional to the weight, a 20Ah battery will be two times heavier than a 10Ah battery.