So Hi everyone ... i want to make a lithium-ion charger using the laptop batteries circuit boards ... but i searched the internet and i did'nt find any information cocerning this porject ... i'm a beginner and most the ICs in the circuit board don't have Datasheets in the Internet so i want to know :
1- How a laptop charge the battery in details please ... how much voltage enter in the circuit board ?
2- How the circuit board charge this cells and how could i control it's charging ... like if i want to charge just 2 cells or 16 cells you see !!
and Thx A lot for your help !?
Since you didnot mention any information about your battery i told you in general:
-this type of batteries use SM-Bus to charge (smart batteries)
-this type of batteries dosen't have charger inside them and charger ic is on the motherboard of laptop,battery only have a few chips for over-voltage protection and in some batteries and eeprom that keeps cycles of battery
-most usual topology of laptop batteries is 6cell (3 series of 2 parallel cells)
mostly 10.8-11.1v (actual voltage is dropped during discharge)
Charging cycle of li-ion battery has 2 modes:
1.Constant current (CC):
usualy 0-70% of charging cycle
In this mode battery voltage would be between 2.4-3.3
2.Constant voltage (CV):
70-100% of charging cycle
3.3-3.9 or even more than 4
This is how you could determine percent of charge in cell,by measuring voltage of battery.
once you put battery in circuit for example put a resistance between +and- current flows and resistor become hot and voltage of battery drops (it called voltage drop)
you can determine life of a bettery by connecting a load and measuring voltage drop of battery if voltage drop was too much it shows that battery is not in a good condition.
one important thing about current and amperage of battery is charging rate and discharging rate defines with C(C is a number that multiplies in battery capacity and shows how fast you can discharge the battery)
li-ion cells usually cant discharge faster than 2c.
for example you can discharge a 3000mah battery with only 6amp (2*3amp)
you could not charge or discharge too fast in this case cell would become hot,dangerous and will explode in couple of minutes.
you can read batteryuniversity.com for more details about batteries.