BShady wrote:I realized by read the earlier post that when putting batteries in series (like li-fe) the voltage doesn't exactly add up like if each sell is 3.6v add them together it wouldn't give me 7.2v. Why?
It does add just like you'd expect. If you don't get the total voltage you expect after seriesing them then you have a problem somewhere.
I found on eBay a 12pcs 18650 Li-ion batteries rated at 5000mah. I'm looking to replace a 6c 5000mah lipo ( which is 22.2v) I'm think that I only need 5-6 and run them in series which would equal 4.2x5=21. Am I correct?
If they're 18650 then I seriously doubt they are anywhere near that capacity. Most likely the seller is making up the specs. There's a lot of threads about various types of 18650, you cna find out from the seller which manufacturer and part number they are, and probably find a thread here or elsewhere about them. If they can't tell you who made them and what model number they are, you can't verify anything about them without buying osme and testng them yourself, and probably shouldn't buy them.
I think you will want to read a lot more threads about various types of batteries before you decide what to buy to replace your existing pack, because it sounds like you still have a fair bit to learn. It's jsut about all here posted already, but will take searching adn reading to find and learn it.
One side qu: what's the difference between mAh and Ah?
It's just SI units, which are documented a number of places, including Wikipedia.