Li-ion tips

Li-ion Safety:

Li-ion cells are used in millions of electronic devices from computers to cell phones to power tools.  If handled properly, they have proven to be very safe and reliable. If used improperly, li-ion cells can be dangerous.  It is important to know and understand the risks of Li-ion cells and also to understand the best practices of handling li-ion cells.

Here are some safety tips:

  • Always follow manufacturer recommended max charging voltage (usually 4.20 ±0.05v)
  • Always monitor your cells during charging.  Never leave cells charging unattended.
  • Never mix different brands and capacities of cells
  • Never mix cells that have greatly different charge levels (ie. 4.20v with 3.8v cell)
  • Never mix worn out cells with high internal resistance with newer cells (ie. cell with 100’s of cycles with a new cell)
  • Never exceed the manufacturers recommended max discharge current (usually 2C for Li-ion cells.  Which is Capacity x2 in amps.  2600mAh @ 2C would be 5.2A)
  • Never open, puncture or modify a Li-ion cell in any way!
  • Don’t mix cell chemistries (ie. Li-ion, with Lifepo4 or IMR)
  • If you manage to discharge a cell to <2.5v resting voltage, recycle the cell.
  • Never submerse the cell in water, or expose to excessive moisture

Li-ion Care:

Properly caring for your Li-ion cells, will increase the cycle life and capacity over the life of the cell.

  • When the cell is not in use, remove it from the electronic device to avoid slow trickle discharging
  • Use lower charge current when possible.  You will get more cycles out of your cell charging at .5C then 1C.
  • When storing the cell for several months or longer, store the cell in a cool place @ ~40%  (~3.8v) SOC (state of charge)
  • Avoid exposing the cell to excessive heat (ie. in your car on a hot summer day)
  • Charge your cells using a proper CC/CV (Constant Current, Constant Voltage) charger.
  • Avoid over-discharging the cell.  2.75v is the recommended cutoff voltage for most Li-ion cells.  This is the lowest voltage the cell should be under load.  Devices with very low current draws may over-discharge a cell and the protection circuit may not protected the cell from overdischarge.
  • Check the voltage of your cells frequently (before and after charging) to make sure you keep the cell voltage within manufacturers specifications.