Batteries are another big component of building an e-board. They are daunting because of the inherent risk of ‘blowing up’ your new system.
In general, there are two main types of battery used in electric skateboards, Lithium Polymer (LiPo) and Lithium Ion (Li-Ion). Both types are dangerous and can cause fires if misused, but both types also provide enough power and are fairly customisable. LiPo is seen as a cheaper and more convenient option while Li-Ion is seen to be more expensive but more reliable and longer-lasting.
There are a few specifications of the battery or batteries:
- Voltage (Volts – V)
- Capacity (Milliamp hours – mAh)
- Discharge rate (C)
Voltage can be described as the potential electrical force in a battery.
There are a few things to clear up when relating this to electric skateboards and batteries.
The voltage can be given a value in volts e.g. 37V, or it could be described as the number of cells connected in series e.g. 10S.
These are the same thing, a 10S system is one that runs at 37V.
This is because all lithium cells (cells are the individual components that make up a battery) produce a so-called nominal voltage of 3.7V and connecting them in series (rather than in parallel) multiplies the voltage. So, 2 cells connected in series (2S) will create a battery with a voltage of 7.4V (2 x 3.7), and 10 cells connected in series (10S) will create a battery with a voltage of 37V (10 x 3.7).
Finding the right voltage for your system – your speed controller and motor should have a max voltage which you do not want to exceed. Most motors for electric skateboards range between 6S – 12S, the higher the voltage the more electrical force. Too many volts and you could end up damaging your components.
The amount of energy stored in a battery is its capacity, and for electric skateboards and hobby batteries, the capacity is usually measured in milliamp hours (mAh) or amp hours (Ah).
1000 mAh is equal to 1 Ah. So, if you had 2 batteries, one with a capacity of 5Ah and the other with a capacity of 5000mAh, their capacities would be equal.
The higher the rated capacity of a battery the longer it will last. In relation to electric skateboards, there are two considerations to remember when choosing a battery and its capacity. One is the weight and the other is the size. As the capacity of a battery increases so does the size and weight, and when adding them to an electric skateboard you ideally want to carry as little weight as possible and make sure you keep enough clearance between the board and the ground.
The C-rating you see on the batteries is the rate at which the battery discharges. You can use the C-rating to work out the batteries maximum output current. It is simply – [C-rating] x [battery capacity] = [peak current output]. So, a battery with a C-rating of 30 and a capacity of 3000 mAh would have a maximum output of 90,000 ma or 90A (30 x 3000). What does this mean?
Well, it’s not recommended that you draw current from the batteries above the given C-rating. So check that the motor you want to get doesn’t have a max amperage above the maximum discharge rate of your batteries.
For example, if we use the above example of the maximum battery output of 90A and we know our motor has a max current rating of 80A, this battery will be adequate to power the motor.