Lithium Polymer Batteries(aka Lipo Batteries)
Lithium polymer batteries are now one of the most used type of batteries of this time. They are very popular in the rc world for putting out a lot of power for such a small battery. They make a very good choice for a lot of projects and you find them in most consumer electronics such as cell phones, electric bikes, rc models and more.There are many benefits to them over NiMH (aka Nickel-Metal Hydride)or NiCd (Nickel Cadmium) batteries.
Most lipos you will find are pouch format, compared the standard cylindrical or hard type lithium-ion polymer battery that you would find in a cell phone. The benefits of being in pouches are that they can be manufactured in any shape and size for many projects and offering a very good power to weight ratio hence the use in e-bike applications,rc heli and plane use.
High discharge rates and capacity size are the real big benefits of lipos as you can run hungry powered applicants for much longer while still being able to provide the power it needs without to much sag on the lipo cell or pack.
As time goes by cells in packs tend to swell and puff up making capacity and discharge go down losing performance in the pack and becoming more unbalanced between the cells and increasing IR (internal resistance) over time. When mistreated lipos can be very dangerous when circuits short, cells get punctured or even possibly a fire can happen as from my past experience in the video. Spending money on a good balance charger is always good as it could be the difference in a good balanced pack or burning your house down which no one wants.
So if you have interest in lipos do good research before hand and have a good understanding as this will help you a lot to get the best performance you want out of lipos, maintain them and have no dangers that may lie ahead in the future.
BE SAFE!