Ive been designing a battery using these cells, after calculating the length of the battery I realized it was directly proportional to the watthours of the battery! heres some math, the cells are 18mm diameter, so to calculate the length of your battery you multiply 18 by the amount in parallel and then the amount in series to get an overall length, batteries like that are too long for my liking so I half them and put them next to each other, so you length is now halved. for example; 12s 7p battery; (18X12X7)/2 = 756mm. watt hours = voltage times amp hours so (12X3.6)X(7X2.5) = 756WH! 10s3p. 18x10x3/2= 270. 10x3.6x3x2.5 = 270 so a simple equation for calculating watthours is Wh=9xSxP. This only works for cells with a nominal voltage of 3.6 and ah of 2.5 like Samsung 25Rcells. This is just a cheeky shortcut, when your building a battery youll still have to calculate total voltage and amphours and whatnot
But a 25r is 18.33mm = 769,86 
But it’s a funny “trick” anyway 
1 Like
I really need to give up plastic rulers and invest in a damn caliper 
well I guess the length and what hours may not be directly proportional but that final equation still works aha. Wh=9xSxP
1 Like
Also amp*voltage = wh 
amperes multiply by voltage gives watts. so amphours x voltage gives watthours, sorry if I wasn’t clear with my abbreviations