Calculating Battery Watt-Hour Rating

To estimate the range on a board, you first need to know how much power the battery can store. We can figure this out by calculating the battery's watt-hour (Wh) rating. By comparing the watt-hours of different packs, we can easily tell which one will provide more range. Unfortunately, board manufacturers don't always provide the Wh for their boards on the product page. Luckily we can calculate this ourselves!

Esk8 batteries are almost always comprised of smaller cells (usually 18650 or 21700) in different configurations. The important info about the configuration is how many cells are in series and how many in parallel. Putting batteries in series increases the voltage while more in parallel increases the amperage. More information can be found here. The number of cells in series/parallel is captured in a format like this: 10s2p or 2p10s. The number before the "s" is the number of cells in series while the one by the "p" is number in parallel. So the 10s2p has 10 cells in series and then two of those in parallel for a total of 20 cells (10 x 2). 10s2p is the same as 2p10s, just different ways of writing it. The 12s3p has 12 cells in series and then 3 sets in parallel for a total of 36 cells (12 x 3).

Calculating voltage first, we take 3.6v (standard cell voltage for fast discharge) and multiply that by the number of cells in series. This number is the total voltage of the battery pack (putting cells in parallel doesn't change the voltage).

Next we need to figure out the amp-hours (Ah) for our pack. This can be calculated by multiplying the Ah in each cell * parallel count. The amp hour per cell is based on the battery model that the pack uses (a common one is the Samsung 30Q). If you Google the cell name with "amp hour rating" you'll find the right value. See the examples below for calculating and make use of the calculator that we've included at the top of the post.

10s2p 3.0Ah (Samsung 30Q cells)
10 series * 3.6v = 36v
3.0Ah * 2 parallel = 6Ah
36v * 6.0Ah = 216Wh

12s3p 3.0Ah (Sony VTC6)
12 series * 3.6v = 43.2v
3.0Ah * 3 parallel = 9Ah
43.2v * 9.0Ah = 388.8Wh

Other resources:
https://dkwan.com/how-to-convert-to-watt-hours/
https://dkwan.com/how-to-estimate-range/