VVT—Virtual Voltage Termination
For Fast Charging Li-Ion Batteries
What is VVT?
Developed, patented and optimized by ICC charger designers, VVT is a revolutionary new technology for safely and effectively charging standard Li-Ion Battery Chemistries up to 50% faster than conventional CC/CV charging.
VVT looks through the resistive losses of a battery pack’s terminals, PCBA, and cell interconnections (or cell pack) to measure Open Circuit Voltage (OCV). By monitoring OCV of the cell/cell pack, VVT allows the charger to charge in the constant current mode longer than conventional CC/CV chargers, greatly reducing the charging time.
Because VVT looks through the battery pack’s resistive losses and monitors cell/cell pack OCV, charging time is consistent over the life of the battery. This is regardless of the degrading condition of the batteries’ or chargers’ terminals or other component aging affects that can increase circuit impedance.
What’s more, VVT actively measures the condition of the cell/cell pack during charge with no additional hardware.
How VVT Works
The VVT enabled charger performs a low frequency switching (on/off) control of the power supply, allowing for a zero current OCV measurement of the cell/cell pack. Once the cell/cell pack OCV reaches a predetermined maximum voltage, the charger switches to constant voltage and the charger monitors the current level to the battery. Charge termination is based on conventional end-of-charge current measurement and termination valve selected based on cell manufacturer recommendation.
The Difference Between VVT and CC/CV
- VVT utilizes voltage sampling to accurately measure cell voltage
- VVT removes series resistance error inherent in CC/CV method
Comparisons:
Both systems charging at 0.7C, 4.2Vpc, C/10 end-of-charge current termination. Battery cell is Sony 18650GT Cells 3.6V, 2.0Ah capacity, 0.3 Ohm resistance between charger and battery cell.
The Results
ICC’s VVT Method Charges
