The S and the P stand for Series and Parallel. So, a 3S1P 1000mAh pack has 3 cells in series, making a 11.1v 1000mAh battery (assuming its a Lipo pack). A 1S2P 2000mAh pack would have 2 cells, but they would be put into parallel, which does not increase the voltage, but would double the capacity. This would mean that it actually had two 1000mAh cells in the battery. So, a 4S2P pack actually has 8 cells, and in this case, each cell has 2100mAh. It has two sets of 4 cells in series that are then put into parallel. I wish I could make a diagram, because it is so much easier for me to explain it that way. Anyways, I hope that this answers your question. A 4S2P pack will act just like any other 4S pack, its just that it actually has 8 cells inside it.
Beware Australian Buyers of on Screen discount vouchers on this site. Hobby King may flash a discount to purchase this item for $82.15 on the right side of the screen. The offer makes you think you are getting a discount. However they claim the price offered is in USA dollars (not Indicated) and the buyer assumes this price discount is in AU dollars. That seems logical being that you are on the Australian Website with Australian Pricing... When you go ahead with the transaction you won't see a discount at all as the Currency conversion will negate the discount.. So in Short its a SCAM to make you think you are getting a special price when in fact YOU ARE NOT!. Very Deceptive and sneaky and I have reported this to the Australian Competition and Consumer Commission as a concern. I have Provided Howard on the support desk a screen shot of the discount offer showing that it does not show the discount in USA Dollars, but he refuses to make the adjustment and apply the discount promised...
Please be aware of this should you get this offer, as you will NOT get any discount off the listed Australian Price.
I have given Hobby King the opportunity to address this problem and apply the discount, but they have chosen to send silly E-Mails that make no sense at all. I have had no choice but to report them and advise others not to fall into this trap... Real shame as I have had good purchase results from them in the past..
I bought this battery for my traxxas slash to upgrade from my 7 cell nimh batteries & WOW...WHAT A DIFFERENCE!!!!!!!! (keep in mind that the stock esc cannot handle this many volts) this battery has great power & runtime for a great price! I was afraid of lipos because of the fire hazzard so I went with these life batteries & I'm very pleased! you'll need a lifep04 compatable charger, I use the thunder AC6 & it works great!