Li-Ion Batterypack Charger IC selection?

[Dirk.S]

Hello Gentlemen

I'm currently working on a Li-Ion charger circuit and have had a look at two different ICs to do the job. Both from Texas Instruments.

The first is BQ24160YFFT capable of delivering 2.5A and the second is BQ24123RHLT capable of delivering 2A.

I am planning to use a 3.7V 6600mAh battery pack. From what I understand you shouldn't charge a battery with a current rating more then 1C. The battery pack consists off 2200mAh cells. So that means that I shouldn't charge with a current of more then 2200mAh but if there are three cells in parallel that means that if I apply a current of say 3A through a Li-Ion charging ic to a 3 cell battery pack the current should roughly split evenly between the three cells meaning that roughly 1A should flow to each cell? Now am I reasoning correct here or not if there is only a positive and negative wire coming out of the battery pack?

My objective is to be able to charge the battery pack with a charge current of 2.1A so that I will be able to charge the battery pack in about +-3.5 hours. Your input is greatly appreciated.

 

[ronv]

You have it right. You could charge it with up to 6.6 amps if you wanted to, but cooler is always better if you have the time.

 

[Dirk.S]

Thanks for the confirmation good sir.

 

[Sangoma]

Li-Ion or Li-Po cells never seem to discharge or charge at exactly the same rate.

When in series this is easier to deal with as you can measure the voltage across each cell and balance it during charging.

In parallel that is obviously not possible without separating them, so if one cells voltage is much lower than the others, it will draw more current. Eventually if they are healthy, they will all end up equal.

In practice the protection circuit on whatever they are powering should prevent the voltage falling too low to prevent damaging the cell, so they should not be too different.

I would not charge at 6A though, without knowing that one cell was not very low, and if it is possible it might be worth being able to charge each cell separately every 10 charges or so.

Last year started to use Li-Ion on projects, cell phone batteries are a very useful voltage, shape and capacity, and most of them have under/over voltage and over current protection built into the package, and some slightly bigger than AA also have built in protection.

 

[WTP Pepper]

The LTM8061 would do the trick. Comes in various versions that can charge multiple cells in series. 2A max output.

https://www.linear.com/product/LTM8061

 

[KeepItSimpleStupid]

Many battery packs have two extra terminals for a temperature sensor. e.g. GPS and cell phones.