All About Batteries
After getting into electric flying a few years ago, I’ve done a lot of asking others for information, reading and learning about batteries. Here are some of the basics that I follow.
Charging
Batteries will be marked with their maximum charge amount, or their charge “C” rating.
While you can charge at a higher amperage, it generally has two downsides: it shortens the battery life, and it raises the risk of catching fire while charging.
The latter is especially important to note. Regardless of how fast you charge your battery, you should always be present to monitor it.
We try to treat our batteries with extra care, so my son and I charge them at a 1C rate. For example, we charge a 2200 mAh battery at 2.2 amps or 2.2A. We charge a 4400 mAh pack at 4.4A.
It does take longer, but the battery does not heat up which helps reduce the risk of fire.
Storage
There are two important aspects for storing LiPos. One is the safe storage voltage, and the other is the manner in which they are stored.
It’s generally regarded best to store batteries at around 40% capacity, which translates to 3.8 volts per cell.
When you purchase a new battery, use a battery checker to see what level it is at. You should see around 40%. This is how battery companies and hobby stores safely store pallets of batteries.
Batteries should be stored in a fireproof container. They can spontaneously combust, even when treated with care. A small 1 cell battery, when ignited, can be enough to burn down a house.
Some people choose to store their batteries in an ammo box. While this is fireproof, it won’t prevent the toxic fumes of the burning battery to fill your house or garage.
Because of this, we choose to store our batteries in a Bat-Safe box. The lid has a filter in it that is supposed to filter out the toxins. You can find them online at MotionRC.com, Amazon.com and more.
While a $60 Bat-Safe box may seem expensive, it is cheap insurance for your house.
Also, one of our past club presidents, Jim Ackleson, relayed a story of a friend that had a battery catch fire in a Bat-Safe and reported that it did, in fact, contain the toxic fumes.
Usage
While using your batteries, its best to not use them long enough that the battery ends up at 3.0 volts per cell. Ideally, it wouldn’t be below 3.5 volts per cell. A target of 3.8 is likely the best. Should it dip below 3.8 volts per cell, it’s a good idea to use your charger in Storage mode to bring the battery back up to storage voltage as soon as you can.
There are many inexpensive battery checkers on Amazon.com for about $10. There are also other more expensive options that offer more functionality, such as the Spektrum Smart Battery Checker that can also drive your servos.
Discharging
To bring your battery down to storage voltage, there are multiple ways to do this.
Using your battery in your plane, vehicle, boat, etc. combined with using a battery checker is the most obvious and fun way to bring the battery to storage voltage.
Your battery charger, in Storage mode, will do the same. However, they discharge at a very low wattage. It generally takes a very long time. Larger batteries, such as a 5000 mAh 6S pack, will take several hours to bring down from a full charge.
After doing some research, I found the ISDT FD-200 discharger. I’ve been very happy with this and have recommended it to others.
When To Recycle
It’s not worth risking a fire with a battery in any of the conditions below. For me, any of these indicate it’s time to discharge to zero volts and recycle.
- Puffy battery, especially if it’s almost round
- Damage to even one cell. Obviously a crash or battery ejection can cause damage, but I’ve also had damage from accidentally dropping a battery from table height.
- The battery charges to full but just doesn’t last anywhere as long as it used to. If I used to get a 5 minute flight, but now it’s at storage voltage after only a couple minutes in the air, it’s time to recycle.
Recycling
LiPo batteries can and should be recycled so the precious metals can be reclaimed.
I have contacted Home Depot directly, and even though their battery recycling boxes near one of the entrances does not list LiPo batteries, they confirmed that we can, indeed, recycle them for us. Also, it’s free.
I believe Batteries Plus may also recycle LiPos but have not researched that.
It’s important to completely discharge the battery as much as possible. Your charger in Discharge mode may do this, but as with the Storage discharge, it will be extremely low. They’re typically only discharging at 5W, which discharges very slowly when you have higher cell packs, such as a 4S or higher.
There are many solutions on the web. Some use 12V light bulbs, others use resistors. I built a variant of this one: https://oscarliang.com/lipo-discharger-light-bulb/
- Brian Sokol