RE: Start of BeagleBone QiCape

danteo — Mon, 29 Oct 2012 10:58:04 GMT

Hi Victor,

I just saw your design. Great.

I'm very happy to see the job done quick and clean by someone.

I think that the goal is achieved and it's a good "pull management" demo in the open source world made by ti and e14.

My opinion was to add a charge controller to the bq5101xx, another cheap mcu for future features and some protection - fuse or a polyswitch but this design serves well the simple requirement made by Shawn.

What confuses me is the R_ILIMvalue that is over 120Ω - the value stated as max in the datasheet of 51013, 13a and 14, but I dont have a bq5 to play with and see what's happening.

Regards,

Dan

RE: Start of BeagleBone QiCape

johnsocm — Sun, 28 Oct 2012 12:06:45 GMT

Hello Victor,

I am a little confused on the BeagleBone Cape you have designed. It seems that the big red box is for the wireless eval kit. When I designed a BeagleBone Cape the wireless eval kit did not fit in between the headers of the cape. I had to do a complete redesign.

Also, when you did the WebBench Designer did you just perform a simple 3.7V min/4.2V max input and a 5.0V output with a 1.0A charge rate Buck Boost? Or did you change anything as far as efficiency, footprint size, or BOM cost, resistor sizes to establish a better design. It seems that the design is just the design that web bench creates automatically, which isn't a bad thing either. But for this design space is definitely a concern.

I am using a battery management system because there are a lot of details to charge a battery under lower power and when efficiency is a must. Here are some things that a simple buck boost will not perform.

Stage 1: CC: Apply charging current to the battery, until the voltage limit per cell is reached.

Stage 2: Balance: Reduce the charging current (or cycle the charging on and off to reduce the average current) while the State Of Charge of individual cells is balanced by a balancing circuit, until the battery is balanced.

Stage 3: CV: Apply a voltage equal to the maximum cell voltage times the number of cells in series to the battery, as the current gradually declines asymptotically towards 0, until the current is below a set threshold of about 3% of initial constant charge current.

Thank you very much for your design and help with the community but I am really confused on how almost all the routing is done because the Qi portion hasn't even been started, unless you plan on just sticking the eval kit on top of the Cape. I guess I would like to see more details.