I would NOT use a "universal" charger for any lithium battery. The exact chemistry type of the cell changes the set point voltages and can't be known by the charger. Additives like cobalt can change the max cell voltage. So I'd look at the pouch label and see what it says. In your case, 4.35V per cell.
If any lithium cell is below 2.5V just throw it away. Irreversible chemical reactions happen below 2.5V that damage the cell. If above this voltage, then the cell is likely recoverable.
7.4V ==> 2x 3.7V cells. This is likely the average voltage of the discharge curve.
I would not charge these cells in series.
You can charge each cell individually using a variable DC power supply and monitor the current till it reaches the cut-off threshold.
Below are some notes I have for my own Li-polymer cells. But generally, the information here is valid for most Li-Ion / Li-polymer cells, with the exception of LiFePo that have an entirely different charge algorithm.
Lithium Polymer (Lipo) / Lithium Ion (Li-ion)
Standard Lipo Charge Algorithm:
If V_cell <= 2.50 V, discard: cell is likely damaged / recovery is unlikely
If 2.50 V < V_cell < 3.00 V, CC charge at 0.05 to 0.10 C (3.00 V compliance limit)
If V_cell >= 3.00 V, CC charge at 0.20 to 1.00 C (4.20 V compliance limit)
Once V_cell = 4.20 V, CV charge until current < 0.10 C
Long-life Lipo Charge Algorithm (~4x cycle life):
If V_cell < 2.50 V, discard: cell is likely damaged / recovery is unlikely
If 2.50 V <= V_cell < 3.35 V, CC charge at 0.05 to 0.10 C (3.40 V compliance limit)
If V_cell >= 3.35 V, CC charge at 0.20 to 1.00 C (4.00 V compliance limit)
Once V_cell = 4.00 V, CV charge until current < 0.10 C
Ultra Long-life Lipo Charge Algorithm (~12x cycle life):
If V_cell < 2.50 V, discard: cell is likely damaged / recovery is unlikely
If 2.50 V <= V_cell < 3.35 V, CC charge at 0.05 to 0.10 C (3.40 V compliance limit)
If V_cell >= 3.35 V, CC charge at 0.20 to 1.00 C (3.85 V compliance limit)
Once V_cell = 3.85 V, CV charge until current < 0.10 C
Precharge | CC 0.05-0.10C, 3.0V compliance | 2.5V < Vcell < 3V
Bulk | CC 0.20-0.70C, 4.2V compliance | Vcell >= 3V
Top Off | CV 4.2V | Icell > 0.10C
Terminate | disconnect from charger | Icell <= 0.10C
CHARGE (voltages WRT charger, not cell)
No energy is stored in a Lipo cell when charged below 3.40 V.
Roughly, charging at 3.40 V (min) provides 0-1% SoC and 4.20 (max) 100% SoC.
Charging a cell when 2.50 V < V_cell < 3.40 volts is pre-charging.
Bulk charging occurs when 3.40 V <= V_cell < 4.10 V (0 to 90%)
3.4 1%
3.5 3%
3.6 5%
3.7 9%
3.8 36%
3.9 62%
4.0 73%
4.1 89%
4.2 100%
STORAGE (votages WRT cell)
Li-ion cells should be stored in a partially discharged state: keep cell voltage
between 3.8 (max) to 3.4 (min) volts for long term storage. This corresponds to
roughly 40% to 0% state of charge.
If cell voltage drops below 2.5 volts, permanent damage will occur.
DISCHARGE (votages WRT cell)
Never discharge Li-ion cells below 2.5 V, as this can cause permanent damage to
the cell.
Terminate discharge at >= 3.0 V for faster recharging.