When it comes to LiPo battery storage, it could mean two things: the charge at which to store the LiPo batteries and how to store them physically. We will be discussing both the topics in this post since they are closely related to each other.
LiPo batteries boast a temperament of their own and can be as large as 10,000mAh 6S packs.
They are quite tricky to charge, discharge and not so easy to store as well. As opposed to your laptop or smartphone batteries which are essentially Lithium-Ion batteries, you cannot afford to leave a fully charged Lithium Polymer battery for a long time.
Any attempt to do so will result in the battery losing its capacity and its lifespan. At worst, it might even start getting puffed up and eventually lose its capacity and lifespan.
The best way to determine the voltage at which to store a LiPo battery is to see the voltage of the battery at the time of its purchase. Manufacturers keep the batteries at storage charge levels since it could be weeks or possibly months before they reach the consumers after the production.
I believe that there is no authentic storage battery voltage as such. But all the batteries that I purchased came with a storage voltage that fell in the 3.8 to 3.85 volts per cell.
So, if you are looking to store your batteries for some time, i.e. for more than four days, then you should bring your battery’s voltage down to 3.8 to 3.85V.
The same holds true if your batteries get discharged completely. If your battery boasts a voltage of 3.7V per cell, you should ensure to get the voltage up to 3.85V before you actually store it.
Batteries should not be kept at a voltage below 3.7V per cell. If you land with a battery pack that is clocked at a voltage lesser than 3.7V per cell, get it recharged very slowly at less than 1C.
Most of the smart chargers available today come with the LiPo Storage option that automatically brings the battery to the appropriate storage charge.
The Imax b6 charger does not determine the charges of all the cell separately while bringing down to storage charge. I had a battery pack which got damaged since its three cells came down to 3.9V and the last cell was not be discharged at all. My battery was at 4.15, 3.7, 3.7 and 3.7V. I believe that chargers do not balance charge since they assume that when you slowly draw current from a battery, all the cells should get discharged equally. The same phenomenon takes place during flight as well but at a higher rate.
You can also configure your timer and voltage alarms on your transmitter so that when you land, the battery is at storage voltage. This will prevent you from toying around with the charger again.
Remember that under load, the voltage is quite low, that is when you are flying and drawing current from the battery. As soon as you stop drawing current from the battery, the voltage tends to go up a little bit.
So, if the voltage alarm is configured to 3.8V in your transmitter, you are going to get extremely limited flight times. Generally, people tend to configure their alarms at 3.4 to 3.6V per cell.
Where to store LiPo batteries
That was all related to storing LiPo batteries electrically. When it comes to storing them physically, things get even trickier.
LiPo batteries consist of reactive elements which are also the cause of them being able to produce so much power. However, that also makes it essential to handle them with utmost care.
You can insulate the terminals at first. This can accomplished by placing a rubber cap or electrical tape on all the terminals including the balance leads and main power leads.
You can also go for a LiPo storage bag. These bags are made of fire-retardant material.
In case the battery catches fire, the bag might not be able to stop the fire but it will definitely give you enough time to react to the situation swiftly.
Here are a few things that you should keep in mind while handling and storing LiPo batteries.
- Store LiPo batteries in locations that are fireproof. You can keep them on the concrete of your garage or in a metal or glass box away from cloth, carpet or wood.
- They should be kept in temperature controlled environments that are dry and neither too hot nor too cold.
- Some people like to store their batteries in ammo boxes.
- You can also keep them in a container with a bag of sand on top. In case of fire, the sand would extinguish fire.
- Keep a fire extinguisher for any untoward situation.
Most of the above mentioned recommendations are related to charging LiPo batteries. While charging a LiPo battery, ensure that it stays in your sight.