Choosing a Battery and a ESC

 Battery

                      The easiest option when it comes to the battery is to buy a premade one. When buying a battery, you need to know the voltage range your ESC can handle. It is often referred to as the number of "S" and "P" of the battery pack. The S is the number of cells in Series, and the P represents the number of cells in parallel. As a common example, we have the 10s2p battery pack meaning 10 cells in series and 2 in parallel. The most used cells in this category is the 18650 size Li-ion batteries (18mm in diameter and 65mm in length).

These batteries have a nominal voltage of 3.7V and 4.2V when fully charged, so 10 of them in series will give 37V nominal (some manufacturers often mark 36V), and 42V when fully charged. Two cells in parallel however doesn't affect the voltage, but increases the battery's capacity and current capabilities. The cell above is the famous Samsung 30Q rated for 3000mAh, two of them in parallel will give 6000mAh. This battery can also provide 15Amps continuous, so two in parallel will give 30Amps continuous. So the current rating is also important when buying a battery pack. If this current rating is low, the board will slow down during hard acceleration and possibly shut down when going uphill. This is know as "Voltage Sag" (when the battery struggles to provide the required current to reach the power necessary to move the board). The range of the board is directly related to the capacity of the battery. Other factors such as the rider's weight, the riding style (fast or slow) and the local relief (vertical elevation of the area, hills...). Going fast or uphill will suck up more power. So definitely aim for higher capacity batteries if your are a heavier person or live in a hilly area, of course it's at a higher price and possibly a bigger battery pack but really worth it.

                                  However, if you want to build your own,  read the step by step guide Here. Knowledge of Li-ion battery is required in order to successfully build a battery pack and know that Li-ion Batteries are a fire hazard, so do not mishandle them. You are not necessarily saving money by building your own battery pack (unless you already have the required tools), but building your own will allow you to design it in your liking and basically get you intended specs (capacity, current, size, weight, shape, etc...).

ESC

The ESC is the brain of the electric skateboard. It receives signal from your remote control, and sends the battery energy to the motor proportionally to the signal's magnitude. There are single and dual ESCs for single and dual motor drives. However, you can use two single motor ESCs and connect them in parallel to the same battery and run them on a dual motor drive. It is a bad idea to use two motor on a single motor ESC.

My favorite single motor ESC used to be the Enertion Focbox (F.O.C box or Field Oriented Control box). It ran FOC mode efficiently and was based on the Vedder Project. 

Unfortunately, the single Focbox was discontinued and a dual version of it was released (even better). Unfortunately, Enertion closed doors not very long ago. No need to worry, there are even better motor controllers from Vedder on the Trampa website.

If these of options are an overkill or above your budget, you can opt for the cheaper version of the VESC (Vedder Electronic Speed Controller) from diy electric skateboard.