Battery Charger and Fuel Gauge

Hello Wang,

We do have multiple offerings that may suit your application. Couple more questions that can help narrow down the options:

• What is your charging current?
• Are the cells removable or are they embedded in the system?

For high accuracy gauging, Impedance Track is a good alternative. If you are planning on having removable battery packs, a system side gauge would be a good alternative. The BQ27500-V130 is not recommended for new designs, I suggest you review the bq27510-G3 for system-side gauging. If the packs are embedded in the system and won't be removed, you can use a pack-side gauge, an option to review would be the bq27542-G1.

Another option would be the bq27426, which included pre-programmed chemIDs.

Regarding the charger, I recommend you review the bq25890 charger. It can provide up to 5A charging, configurable through I2C, can be powered via USB or an adapter and include D+/D- detection.

Hope this helps.

Thanks.

Hello Wang,

Typically pack side gauges provide more accurate gauging since they are connected directly to the cell tabs and are typically located near the cells. System-side gauges reside on the system board and include mechanisms to detect battery insertion when a new pack is connected; this is for systems that would use a "dumb" pack or for applications were the user can change the packs themselves. 

You would only need one bq25890 and one gauge. Even though you have more than one cell in parallel, a 1SXP configuration is still considered a single-cell application. Our gauges provide monitoring of safety conditions such as over-temperature, over charge/discharge conditions, short circuit detection, etc. For a single-cell 1SXP application you don't need cell-balancing, as the cells will balance themselves.

Thank you.

Hi Fernando,

From your explanation, i assume the configuration of my battery system should be as below?

Please advice...

So, BQ25890 will charge these 2 Li-Ion simultaneously as mentioned right?

As you mentioned for cell balancing, does it mean both Li-Ion battery level will be the same after being used for some time?

So, BQ27542-G1 only track either one of the Li-Ion battery fuel gauge only?

Thk,

Br,

Wang

Hello Wang,

The block diagram seems correct. The 890 will charge both cells in parallel at the same time, then they will balance themselves. The bq27542-G1 will monitor both cells in a 1S2P configuration, remember that a 1S2P is still considered as one cell, so the gauge will monitor the voltage of the two cells in parallel and the current flowing through both cells.

Thank you.

Hello Wang,

The bq27542-G1 does not have a cell-balancing algorithms, this is a feature for our multi-cell gauges. 

Parallel cells share the same voltage, hence why they don't require cell balancing. The impedance mismatch between the cells should be minimal if using well matched cells, which may cause a slight difference in the charging current, but still should regulate to the charging voltage.

Thank you.

Hello Wang,

The minimum number of cells in series the bq78350 can handle is 3s; the application we have been discussing is 1s, I don't think the bq78350 will work for this application.

Hi Fernando,

We revise the requirement to 4s in parallel.

Please refer below revise diagram...

In this case, we choose bq76920 fuel gauge because it can support from 3S to 5S cell and integrated with cell balancing FETs.

The TI also suggest that we use bq78350 as the gas gauge and battery management controller.

Currently we are thinking whether or not we can skip the bq78350 and direct interface the bq76920 with the host (MCU) through I2C.

This is because bq78350 interface with SMBus and it is just a companion to bq769x0 series for SMBus host interface and LED purpose.

Please advice.

Thanks,

Br,

Wang