Most people don’t use their batteries often enough for any of this to matter long-term. Consider the following. Good quality batteries nowadays can be bought for $20. Let’s assume 300 charge discharge cycles per battery. Most people don’t even charge their batteries once a week. Do you see where I’m going with this.
My advice would be to get high quality batteries and a good-quality charger. Try not to charge unattended. And use the batteries in whatever way is most convenient to you. But if I had to pick a voltage as a cutoff from when to start charging it would probably be 3.7 V.
In the meantime here are a few basic facts to get you up to speed on lithium’s.
- Charge between .6C to 1C. .6C is considered the ideal .
- Lithium-ion is a very clean system and does not need formatting when new. Formatting makes little difference because the maximum capacity is available right from the beginning. Nor does a full discharge improve the capacity once faded. In most cases, a low capacity signals the end of life.
- Lithium-based chemistries should be stored at around a 40 percent state-of-charge (SoC).
- The SoC of Li-ion is roughly 50 percent at 3.80V/cell and 40 percent at 3.75V/cell.
- Allow Li-ion to rest 90 minutes after charge or discharge before taking the voltage reading to get equilibrium.
- All batteries must have the ability to relax after charged, even when kept on float or trickle charge.
- Discard Li-ion if the voltage has stayed below 2.00/V/cell for more than a week.
