LiPo charge in circuit 2S1P 7.2V stack

[SL4P]

I'm working on a project where I have to use 5V0 rather than 3V3 as Vcc

I could use a converter to push a (larger) 3V6 cell up to 5V/regulated, but would rather use 2x 2000mAh 3V6 Li-Xx cells to start high and regulate down. 

Load is around 1200mA sustained from the battery pack, so a 500mA charge would be desirable.

All the integrated charger chips I see online are for single Li-Xx cells.
Does anyone have a hook into a multi-cell charger chip / schematic for cell balancing etc.

Batteries are not removable in this application (an IP rated hand-held enclosure)
--- or I could consider an OEM charger brick + cell kit that slides in to the handle like power tools. ??

Thanks

[ohmineer]

There are some integrated chips that charge 2S1P cell stack.
No sure if this is what you need but Take as an example these models:
- Microchip MCP7384X (http://ww1.microchip.com/downloads/en/DeviceDoc/21823D.pdf)
- TI BQ24133 (http://www.ti.com/lit/gpn/bq24133) and TI BQ24170 (http://www.ti.com/lit/gpn/bq24170)

Regarding to cell balancing, AFAIK it is not very used in battery packs with only two cells.
In any case, you can also take a look at BQ29200 (http://www.ti.com/lit/gpn/bq29200) model from TI.
Depending on the balancing current you want, the circuit can be very easy to implement.

[kaindub]

Hi SL4P
have a look in Silicon Chip magazine April 2014 (www.siliconchip.com.au)
I published a circuit that charges 2S Lipo from 5V (USB) and has cell balancing. Charging current is 250ma ( matched to the capability of USB ports)
You can adapt it to any input voltage and output current with a few component changes. Uses an MC34063 chip.
I designed it to be incorporated into equipment, similar to your needs

Robert

[SL4P]

Thanks - both excellent refernces.
I was trying to get April SC - but everyone's out of stock.
Cheers

[amyk]

I could use a converter to push a (larger) 3V6 cell up to 5V/regulated, but would rather use 2x 2000mAh 3V6 Li-Xx cells to start high and regulate down.

Why is that? Parallel cells don't require any balancing (as long as they're balanced to start with, they'll stay balanced) and you'd have to use a boost converter anyway if you wanted to charge from USB (500mA).

[SL4P]

2S = serial