Battery charger circuit

[hansika]

HI all,
i want to charge a li-ion battery cell(3.7V) with charger circuit , i am having 24V as input for the
battery charger what my doubt is is there any ic which will take 24V i/p to charge 3.7V or 4.1V cell and how this will occur with constant current or constant volatge which is the better option for li-ion battery.

 

[Dragon Tamer]

The problem with Li-ion batterys is that you need an IC that was specificly made for charging Li-ion battery. They are very sensiteve to over voltage and can easisly catch fire if they are not properly regulated. I would recomend using a much lower voltage. One that is much closer to the voltage of the battery so you don't destroy it accidentaly.

The best that I can recomend is that you go to a website with data sheets and you search for Li-Ion chargers and see what comes up. The problem is that we don't know exactly how many cells your battery is.

 

[hansika]

i have searched for the charger ic and found one ic can you please see its data sheet and tell me whether it is suitable for my application or not, ia m new t this type of application so i need suggestions from the people like you please help me in this thanks in advance. the ic is MAX1737.

 

[hansika]

Hi all i am having some small doubt in battery charging using max1737. according to the data sheet of max1737 it can charge up to 4 lithium cells in series. what my doubt is i am having a battery pack of total 8 li-ion cells connected as two 4 cells are in series connected as parallel can we charge this package with the same IC(max1737). thanks in advance

 

[Sceadwian]

hansika, packs are not easy to charge, you would have to charge each half of the lithium pack separately, so you'd have to charge each series string isolated from each other using a single charger. You can not charge lithium batteries in parallel safely without much more advanced charge control, even in series you should monitor each cells voltage seperatly.

The typical charging scheme for a single Lithium cell is a constant current source of 1/2 to the full mah capacity of the cell until the voltage of the cell reaches 4.1 volts, and then you supply a constant voltage of 4.1 volts until the charging current reaches 1/10th of the cells capacity. Something else to consider is you have to monitor the battery for under voltage as well. Thermal monitoring of the cell is advisable as well, because under normal charging conditions a lithium battery will NOT heat up when it's charged, they have a 99.8% charge efficiency. If it heats up during charging it's a sign that there is something seriously wrong. Over charging and over discharging the cell will cause the chemicals inside to either passivate or plate out to and the cell becomes useless.