User Guide

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Guide to Lithium Polymer Battery’s

Heat causes the excess oxygen to build up more and more. Eventually the LiPo

pack begins to swell (due to the oxygen gas build up). This is a good time to

stop using the battery – it’s trying to tell you that it has come (prematurely or

not) to the end of its life. Further use can, and probably will, be dangerous.

After the pack has swollen, continued use can cause even more heat to be

generated. At this point, a process called Thermal Runaway occurs.

A Swelled, or Puffed, LiPo

Thermal Runaway is a self-sustaining reaction that is accelerated by

increased temperature, in turn releasing energy that further increases

temperature. Basically, when this reaction starts, it creates heat. This heat

leads to a product that increases resistance (more Li2O), which causes more

heat, and the process continues until the battery bursts open from the

pressure. At this point, the combination of heat, oxygen, and the humidity in

the air all react with the lithium, resulting in a very hot and dangerous fire.

However, even if you stop using the battery when it swells, you still have to

render it safe. If you puncture a LiPo that has swollen and still has a charge, it

can still catch fire. This is because the unstable bonds that exist in a charged

battery are in search of a more stable state of existence. That's how a battery

works; you destroy a stable chemical bond to create an unstable chemical bond.

Unstable bonds are more apt to release their energy in the pursuit of a more

stable bond.

When a LiPo is punctured, the lithium reacts with the humidity in the

atmosphere and heats up the battery. This heat excites the unstable bonds,

which break, releasing energy in the form of heat. The Thermal Runaway starts,

and you again get a very hot and dangerous fire.

The entire process of building up that lithium oxide usually takes around 300-

400 charge/discharge cycles to reach a tipping point. That's a typical lifetime of

a LiPo battery. But when we heat the batteries up during a run, or discharge