bq246xx cell monitoring and dc input

Rishab,

Even though the bq246xx family of devices can charge up to 6 cells in series, it is recommended that the battery pack health is monitored via some type of gauge. Here are some devices that can monitor the health of a multi-cell pack: www.ti.com/.../battery-fuel-gauge-products.page;4 Cells&o4=ACTIVE&p338=Li-Ion/Li-Polymer.

"AC input pins" is still a DC voltage/current input. They are referred to as "AC inputs" because AC wall adapters (AC to DC adapters) are commonly used as input sources in applications.

Thanks for clearing that up

If I use a bq76920 then I do not need a bq246x? The bq76920 is capable of driving charging and discharging FETs?

I want to charge 4 li ion cells in series and be able to roughly gauge their remaining capacity while also balancing the cells and charging them.

Would the bq76920 be a good solution for this?

Rishab,

The bq76920 is only a protection IC. It does not actually charge the battery.

Could you describe your application and setup in more detail? This will allow us to suggest a solution. We do have a one-chip solution that integrates a battery charger, a gas gauge, and protection - it's the bq40Z60.

Hi Smriti

I am developing a portable speaker. I need something that can charge 4 li ion cells ( 14.4 -16.8v) in series while also protecting and balancing the cells in the pack.

I should probably add:
the system will be charged using an ac->dc wall adapter.

Rishab,

Are you making your own battery pack or buying a pack from a battery vendor? If you are buying the pack from a vendor, the pack will already have protection built in, in which case, all you need is a battery charger. Do you also need gauge functionality?

FYI - we have a few TI Designs for portable speakers here (they aren't 4 cell solutions, but it should give you an idea of what the architecture looks like for a system solution): www.ti.com/.../refdesignsearchresults.tsp

I will be purchasing unprotected 18650s in bulk so I will need an IC with protection. I also need a very rough estimate of battery level which can probably be estimated by looking at cell voltage.

I was looking at the BQ40z60 ic that you suggested and the only problem is lacks i2c. Can I communicate with it using i2c through its SMBUS pins? I think the battery gauge on this chip is overkill for the application.

Rishab,

SMBus and I2C are similar but also have notable difference so you can't communicate with a SMBus slave via a I2C host in a straightforward fashion. See this application note for the differences between the two protocols:

 

So if i understand correctly, your requirements are as follows?

1. I2C control for charger and battery protection (gas gauging optional?).

2. 4S Li-Ion battery. Max target charge voltage is 16.8V? What is the desired charge current?

3. What is the input adapter DC voltage?

Any other requirements?

Thanks for your response Smriti

1. yes

2. yes, the desired charge current is about 2.4A but willing to work with 2.0A.

3. either 12v or 19v. 

other requirements: cell balancing is highly desirable

Rishab,

Let's take the rest of the discussion offline. I have sent a private message to you with some comments and questions.