Survey 2S1P Battery Balance Solution

Hi Wen,

If you just want to balance then i would recommend using the bq29200 or the bq29209 which is an OV protector that has cell balancing.

Thanks

Hi Sir,

Thanks for your response. bq29200 or the bq29209 is good device.
BTW, may I know TIDA-00982 and TIDA-00449 which suitable our application? bq76920 with MSP430 can equivalent bq4050?

WEN

Hi Wen,

The bq4050 could help you for an all in one solution that does protecting, gauging, balancing, monitoring etc.

Thanks

Hi Sir,

Could help us to review schematic or comment this? thanks.

bq29200.pptx

WEN

I reviewed your schematics of the bq29200 portion.

Few noted d/s errors that need to be highlighted.....

 

on  pp10 of the d/s. the CELL1 balance current,  RCB1 does not come into play;

 

I(CB1) = V1/[RCB)+Rint]

 

During CELL2 balancing , current is sourced  by VDD ( internal LDO)

 

I(CB2) =(V2-V1)/ [RVD+RCB + Rint]; hence the non- dependency of RCB2.

 

 

Assume Rint = 250 ohm( max)  for the internal FETs.

 

 

 

Hi Sir,

Thanks for your comment.

for BQ29200 operation question also need you help.
1. May I know BQ29200 OUT PIN change form low to high when OVP status or un-balance status?
2. BQ29200 How to know battery un-balance status?
3. BQ29200 How to setting V2 and V1 dropvoltage for battery start balance? and minimun dropvoltage can start balance?

WEN

Hi Wen,

Here is the answer to your questions.

1. Bq29200 OVP is 4.35V.

2. This is auto cell balancing with external enable control. If enable the /cb_en pin then it will automatically balance two cells if they are off by 30mV.

3. i think I combine the answer with #2 question. Please check out the datasheet and it has lot more details.

Hi Sir,

Thanks for you quick response.
1. each cell over 4.35V, OUT PIN change from low to high, right ?
2. I can measure V1 and V2 and /CB configure to GND.
if dropvoltage > 30mV, BQ29200 automatically balance two cells.
if dropvoltage < 30mV, BQ29200 stop automatically balance two cells.

1. Yes, either one goes above 4.35V.
2. Yes... the diff of two cell is greater than 30mV. example. Vc1= 4.3V , VC2= 4.331V then cell balancing is ON.

Hi Sir,

this design is reference d/s.

could help provide example to me? since MOSFET Rint is not found d/s.

Hi sir,

for charger and balance operation. which one is good?
1. Charger completed then MCU let /CB pull low (balance)
2. Charge battery and /CB pull low (balance) always pull low(balance).
3. Charge battery after discharge battery to low level then MCU let /CB pull low (balance)

for 8.3.4 Cell Balance Enable Control
need to use MSU monitor battery voltage to enable balance status? or HW configure, which one is better.

"To avoid prematurely discharging the cells, it is recommended to turn off (pull high) the active-low Cell Balance
Enable Control pin at lower State of Charge (SOC) levels"

Hi Wen,

For chargers please use the charger forum, as they are the experts and would be better suited to answering a charger question.

Thanks

Miguel

refer to the CB equation and Rint value given to youe questions on Jan 5th post.