charging 2 lithium ion batteries in series using Power Management IC

[ferdowssanehi]

hello everyone 

I am doing a 3rd year project and i was wondering which power management IC i should use to charge "two" 4.2V lithium ion batteries which are in series.
My project uses a solar panel which has a maximum voltage output of 17V. My circuit also uses a micro-controller Atmega328p to control the DC/DC converter circuit by suppling it with PWM.

I am hoping there is a IC chip that i can use with my micro-controller. I am familiar with I2C and SPI.

I am looking forward to all your responses   

Thank you.

[Kryoclasm]

I may be wrong, but from my RC helicopter hobby days, LiPo's need to be charged in parallel.

Each cell needs to be monitored for over charging.

You can still use it in series, but unless something has changed in the last few years, the charging is parallel, so you might not find any chips that would support series charging.

Would like to know myself if this is right.

[sleemanj]

I may be wrong, but from my RC helicopter hobby days, LiPo's need to be charged in parallel.

Multi cell balance chargers charge predominantly in series (assuming a  battery of series cells), the balancing lines are used specifically to balance cells (there are various methods), not for providing the bulk charge current, as I understand it.

Probably more than you ever wanted to know about balance charging:
http://focus.ti.com/download/trng/docs/seminar/Topic%202%20-%20Battery%20Cell%20Balancing%20-%20What%20to%20Balance%20and%20How.pdf

[RoadRunner]

i am not sure if this will solve your purpose but i have used TI BQ2057T for charging two Li-Ion in series.

http://www.ti.com/product/bq2057t

but the maximum input they accept is 15V

[amyk]

i am not sure if this will solve your purpose but i have used TI BQ2057T for charging two Li-Ion in series.

http://www.ti.com/product/bq2057t

but the maximum input they accept is 15V

TI also has a bunch of other Li-Ion monitor/charger ICs you can take a look at.

[Neilm]

If the cells are not impedance matched then balancing will be required when charging in series.

[toxicnos]

I don't know of charging in series is a good idea because the cells voltages may become unbalanced. You could use a lipo balance charger if your solar panels put out the output for it.