Ask twenty persons about how to store battery packs and there is good chances, you’ll have twenty different techniques. Why? We don’t really know. The same phenomenon happens with nitro engine break-in procedures. I believe this is part of the hobby. So, here is a guide to store your battery packs safely and to extend their life.
Important note: This article is intended for persons experimented with NiCad, NiMh or LiPo batteries. Please, make sure your battery packs are in excellent condition before storing them. Always follow the manufacturer instructions included with your battery, charger and with your balancer when manipulating batteries. Always store your battery packs in a dry, well ventilated safe place at room temperature. In case of doubt, please refer to your battery manufacturer before continuing.
NiCad battery packs are less popular those days but people still use them. There are two options for NiCad batteries. The first one is to store them fully charged and re-peak them every two or three weeks to make sure they still fully charged. The second option is to fully charge your pack and the fully discharge it before storing. Never store your NiCad packs partially charged, this will increase the memory affect of the cells and can ruin your pack.
The best way to store your NiMh packs is to fully charge it. NiMh cells have tendencies to discharge by themselves. You must re-peak them every three or four weeks to make sure they still topped off. NiMh battery packs don’t need any special maintenance, just keep them fully charged.
A LiPo cell should never dropped below 3.0v (3.2v to be safe) and never goes higher than 4.20v. Pay close attention to each cell of your pack. This is not because a 2S pack shows a total of 6.2v that it means that it is safe. A cell could be at 2.9v while another cell might be at 3.3v totaling 6.2v. Make sure you have a charger or a balancer that let you read voltage from each cell. There are two good options that come when storing LiPo packs. The first one is to fully charge your pack at its full capacity and re-peak the pack every two or three months. The second option is the most common. Charge your LiPo pack at 70% of its capacity and check your pack voltage every two or three months. What does it mean? It simply means that each cell’s voltage should be somewhere between 3.75v and 3.85v. Because LiPo packs don’t discharge by themselves, you can check them every two or three months and recharge them at 70% if needed.