Difference between Lithium Polymer batteries of varying capacity and cell amount

Question

I was looking to purchase a LiPo batteries online for a side project. Upon shopping around, and reading up on LiPo batteries, I have a fair understanding on what the numbers/letters on the battery packs (i.e mah,S,C, etc).

However, I noticed a wide variety of battery packs on sale, ranging from a 5000mah 3S LiPo battery pack to a 4500mah 4S and 5000mah 6S LiPo batery pack. My question is, is there any rule of thumb when it comes to mah ratings and the number of cells in a battery pack? For example, given the examples above, I would assume that the 5000mah 3S refers to the entire (3 Cells) capacity of the battery pack, with the same applying to the 6S battery pack. However, why then is the 6 cell pack more expensive than the 3 cell battery pack?

If I were to divide the mah rating equally among the number of cells in a battery pack, the 3cell pack would have 1666.67mah per cell, which is FAR more than the 833.33mah per cell in a 6cell battery pack.

OR, am I mistaken and the 5000mah refers to each individual cell in a battery pack, therefore the 5000mah 3S battery pack would have a total of 15000mah, and the 6S battery pack would have 30000mah in total, which would make it's higher price justified.

Could someone clarify this please?

Answer 1

What you are missing is the voltage. You're paying for energy storage, not for mAh. If you put n cells in series, the mAh does not change, but the energy stored is n times as much, because that's how much more voltage you have. Since they're in series the current (mA) through each is the same.

Some batteries are rated in W-h (watt hours) which is directly proportional to the energy stored (1 W-h = 3,600J),