d123
Advanced Member level 5
Hi,
Curiosity: I am trying to understand Li-ion cell charging, not a battery pack which needs charge balancing. Have read a few web pages and pdfs so far. I have understood the following:
> Ideal usage (i.e. discharge) temperature is 18°C to 21°C.
> Discharge to ~10% to 20% and no lower.
> Charge to ~90% or is 100% fine?
> Allow to discharge to ~10% to 20% before charging to maximize lifecycle.
> Do not allow a cell to fall below 2.5V.
> Can use/discharge from -20°C up to +60°C (or preferaby +55°C).
> Can fast charge from +5°C to +45°C. Below +5°C, need to reduce charge current. Do not charge below 0°C.
> Self-discharge is ~3% to 5% per month and must recharge at least every 12 months.
> Store at ~ 40% to ~50% charge, not 100%.
> Charging is implemented via constant current at a steadily increasing voltage then at a constant voltage above the battery's nominal voltage.
a) Are the above points correct/factual?
b) Is sensing low voltage and nominal voltage a way of knowing when to charge and when to stop charging the cell?
c) What in real, practical, circuit implementation terms does the last point mean? Can you e.g. charge a 3.7V, 1A cell at, for example, a fixed 100mA and fixed 4V continuously from 2.5V to 3.7V and then disconnect the charger or is the method more complex than just using a CC source until nominal voltage is reached? How is the 10% to 20% sensed and how is fully-charged sensed - via the cell voltage only?
TIA
Curiosity: I am trying to understand Li-ion cell charging, not a battery pack which needs charge balancing. Have read a few web pages and pdfs so far. I have understood the following:
> Ideal usage (i.e. discharge) temperature is 18°C to 21°C.
> Discharge to ~10% to 20% and no lower.
> Charge to ~90% or is 100% fine?
> Allow to discharge to ~10% to 20% before charging to maximize lifecycle.
> Do not allow a cell to fall below 2.5V.
> Can use/discharge from -20°C up to +60°C (or preferaby +55°C).
> Can fast charge from +5°C to +45°C. Below +5°C, need to reduce charge current. Do not charge below 0°C.
> Self-discharge is ~3% to 5% per month and must recharge at least every 12 months.
> Store at ~ 40% to ~50% charge, not 100%.
> Charging is implemented via constant current at a steadily increasing voltage then at a constant voltage above the battery's nominal voltage.
a) Are the above points correct/factual?
b) Is sensing low voltage and nominal voltage a way of knowing when to charge and when to stop charging the cell?
c) What in real, practical, circuit implementation terms does the last point mean? Can you e.g. charge a 3.7V, 1A cell at, for example, a fixed 100mA and fixed 4V continuously from 2.5V to 3.7V and then disconnect the charger or is the method more complex than just using a CC source until nominal voltage is reached? How is the 10% to 20% sensed and how is fully-charged sensed - via the cell voltage only?
TIA