Hello my dear colleagues,
I'd like to find informatior or expertice, about what is the maximum value of Voltage that I should apply between terminals in oder to proceed to charge or recharge the batteries used in solar system?.
For instance, if we have a battery of 6 V which is the maximum value that this cell is able to support without produce damage in it?.
I'd thanks whatever information about it!.
Thanks in advance!.
A new single Li-Ion cell has approximately 3.7 V with 40% charge when out of manufacturing unit. When fully charged at 100%, its charge cut off is 4.2 V. For 3.6 V cell, charge cut off is 4.1 V. These cells can be discharged upto 3.3 V.
For a 6.4 V battery pack, I found charge cut off voltage to be 7.3 V and discharge cut off to be 4.0 V.
As a general rule 86-87% is acceptable, increasing charging voltage above this range is found to have detrimental effect on cell life cycle.
Dear Tony,
A battery is characterized by a maximum voltage Vm when it is fully charged. It is also characterized by a nominal operating voltage Vn,which can be considered an average voltage. When discharging, the voltage starts at Vm maximum and quickly drops down to about to Vn for the majority of the battery life. If the voltage of the battery is decreased by further discharging, the battery will be dead and finally it reaches the cut off voltage at which the the load must be disconnected from the battery.
For details about the discharge profile of a Li-ion Battery please refer to the link: https://learn.adafruit.com/li-ion-and-lipoly-batteries/voltages,
When charging the battery by a constant voltage source you have not to increase the the charging voltage source more than Vm since the battery will be overcharged where most of the charging energy will be lost as heat and formation of bubbles which can be dangerous for the battery.
So the charging circuit must be made off once the maximum voltage has been reached.
There are good schemes to charge and discharge the batteries. For more details please refer to the paper:Article Enhancing the design of battery charging controllers for pho...
You can see also the chapter on the batteries of the course in the link: https://www.researchgate.net/publication/236002879_A_course_on_photo-voltaic_array_systems
The battery specs completely depends on the type of cell you are using, Even though you are using Li-on there are different types with different chemistry.
For Example , a 4.2 V Peak Cylindrical cell can be charged till 4.1 V and its safe and even if you charge to 4.2 V you don't face any issues basically its Trickle Charging, and we often do this in our mobile phones.
The nominal is 3.6 V and the discharge will be vary slow from 4.2 to 3.6V. its same during Charging as well in most of the cells.
The DOC is 2.5 V, We should not discharge the cell below this voltage. The voltage drop will be quick from nominal to 2.5 V. So, in this case the Min voltage that should be charge is > 2.5 V. its better to use battery in between Nominal and Peak rather than discharging it completely to 2.5 V which is not good for Health of Battery.
Better check the data sheet of your cell and follow according to the Charge and Discharge curves.
Dear respected Tony Castillo-Calzadilla,
The solar panel to be connected to the terminal of the solar battery to charge it must have a voltage that must be a little greater than the norminal voltage of the solar battery but must not be less than it.
Best regards.
Kifilideen.
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