Lithium Polymer batteries (commonly known as LiPo batteries) are in my opinion, the fickle toddlers of the battery world. They’re widely used by hobbyists, makers, and R/C enthusiasts but we also often times see them in laptops, cell phones, tablets, etc, too.
I say they’re the fickle child of the battery world because any mistake can result in what they call a “catastrophic failure”. Look at it wrong? Catastrophic failure. Breathe on it too hard? Catastrophic failure.
Okay, maybe not that dramatic, but seriously: over-charge, over-discharge, high temperature, any kind of puncture or a short circuit are some of the main things that can cause these bad boys to leak, inflate or catch fire.
But we will discuss that kind of
fun dangerous stuff further later on in this post.
These batteries are always labeled with a bunch of numbers. They represent the ratings/specifications and there are a few that are important to pay special attention to. This includes the capacity, usually in mAh, is a rating that basically (without delving into the technicalities) tells you how much the battery can hold. If you look you’ll find something that looks like “#S”, where # is the number of cells the battery has and the S indicates the cells are in series. There also should be something on the battery that resembles a Discharge (C) Rating. The C Rating is how fast the battery can be drained without being permanently damaged.
This being said, these ratings should be followed with care. There are special chargers for LiPo batteries that help ensure no over-charging occurs. They come with variable current and voltage settings, but are known as Constant Current/Constant Voltage (CC/CV) chargers.
The nice thing about these is that they come with balance boards which the LiPos can plug directly into allowing the charger to keep track of how much voltage has been loaded onto the battery.
Taking safety measures is always a good idea when it comes to LiPo batteries. You should never, ever… EVER, leave a LiPo battery charging unattended. Even with all the safeguards, they can still over charge. Just a few weeks ago we plugged one of our LiPos in to charge and it immediately began to expand like a balloon. User error was responsible, but the point here is that these are very easy mistakes to make.
Steps can be taken to actively avoid most problems. For example, we keep buzzers on our batteries. These buzzers beep (with the approximate *volume equivalent to one penguin herd or 10,000 hummingbirds) when the battery voltage hits a certain minimum threshold.
*Not an official specification
If you over-drain a LiPo battery, it can no longer be charged – even worse, if you try to charge one that’s been over-discharged, it may inflate, explode, or become sentient and take you hostage.
An easy way to feel extra safe when charging LiPo batteries is to buy a LiPo safe, explosive proof bag. If you charge them in this anti-Skynet bag, you will at least be safe if the battery starts smoking or gets any other wild ideas.
Where can you find these explosive proof bags you ask? In the Amazon category “Toys & Games”. So if you don’t think explosions are all fun and games please do consider this purchase.
This was the battery afterwards – it didn’t explode but the wires were seared off completely. We stuck it in our LiPo safe bag and left it alone, to think about what it had done.
One of the valuable lessons we learned with these batteries when preparing a project, especially for a live demo is to anticipate and get ready in advance to avoid issues… especially if issues can include the death of your battery.
If you have any questions regarding whether or not an intended application might harm your delicate LiPo, please feel free to ask on the Digilent Forum!
Fortunately as with most things if you treat your LiPo batteries with care, and they will be less inclined to explode.