What's Left in the Tank?
This volt meter is super tiny, minimalist, and just plain cool. It's hand-made by CandlePower Forums member "Cottonpickers." He sells them to fellow members and I thought they were such a great idea I wanted to bring them to you!
The meter is intended specifically for use with lithium-ion batteries. It will not work for alkaline, NiMh, or disposable Lithium batteries (eg. CR123) because they don't have enough voltage to drive the display. .
Each wire is terminated with a small rare-earth (Neodymium) magnet that will stick to the positive and negative terminals of your battery. Just hook it up and read the voltage!
Lithium Ion batteries are at 100% charge @ 4.2V and should be recharged when they are below 3.8V. Voltage is related to battery capacity (for Li-Ion):
4.2V = 100%
4.1V = 90%
4.0V = 80%
3.9V = 60%
3.8V = 35%
3.7V = 10% (Recharge before this level to prolong battery life!)
3.5V = EMPTY