BQ25616: Charging parallel cells

Dice-K

Mastermind 7029 points

Part Number: BQ25616

Tool/software:

Hi support team,

Does the BQ25616 support operations such as charging for 1S2P or 1S3P batteries?

Regards,
Dice-K

4 months ago

0 Michael Emanuel35 4 months ago

TI__Mastermind 36495 points

Hello,

It really depends on the capacity of the batteries and whether or not there is enough charge current from one charger to supply all batteries.

Regards,

Mike Emanuel

0 Dice-K 4 months ago in reply to Michael Emanuel35

Mastermind 7029 points

Hi Michael,
Thank you for your reply.

What is the total capacity that one BQ25616 device can handle?

When using 3 in parallel, the charging current is divided into 1/3, but whether it is exactly 1/3 depends on the battery, and there is no way to control it?

Best regards,
Dice-K

0 Michael Emanuel35 3 months ago in reply to Dice-K

TI__Mastermind 36495 points

Hello,

Assuming the input is sufficient, the device can charge up to 3A and only provide a total of 3.2A out of the switch node. If the batteries were equal voltage that would be roughly 1A per battery. Again, the total charge current out of 1 charger is 3A.

We do not provide way to control how much current goes into each battery. Careful connection and balancing of the impedances in the path can help to potentially meet this goal.

Regards,

Mike Emanuel

0 Dice-K 3 months ago in reply to Michael Emanuel35

Mastermind 7029 points

Hi Michael,
Thank you for your reply.

Are there any ICs other than the BQ25616 that support parallel charging of multiple cells?

Best regards,
Dice-K

0 Wyatt Keller 3 months ago in reply to Dice-K

TI__Guru** 104905 points

Hello,

If the cell impedances, or as Mike mentioned the series resistance of the power paths to each cell, is not the same, there will be slight imbalances of each cell when charging stops. This will be the same regardless of the charger you select since it is a system level behavior.

Some steps from the charger side to improve this behavior is to decrease your taper current, so the IV effects have minimal impact on parallel charging. Otherwise system level impedance matching would be helpful and matching cells with very similar capacity and impedance will reduce any imbalances during charge.

Sincerely,

Wyatt Keller

0 Dice-K 3 months ago in reply to Wyatt Keller

Mastermind 7029 points

Hi Wyatt ,
Thank you for your reply.

I have understood that there is no IC that fully supports parallel charging of multiple cells.

By the way, is there a way to control the taper current?

Best regards,
Dice-K

0 Michael Emanuel35 3 months ago in reply to Dice-K

TI__Mastermind 36495 points

Hi Dice-K,

In Constant Voltage mode the voltage is regulated, not the current

Regards,

Mike Emanuel

0 Dice-K 3 months ago in reply to Michael Emanuel35

Mastermind 7029 points

Hi Michael,
Thank you for your reply.

There doesn't seem to be any way to control the taper current either.
Is there any other way than to use one charging IC for one cell?

Does TI have any devices with parallel control like the MAX17332?
www.analog.com/.../max17332.html

I looked at the following thread, but I don't know if it supports parallel charging.
e2e.ti.com/.../bq25186-max17332-replacement-recommendations

Best regards,
Dice-K

+1 Michael Emanuel35 3 months ago in reply to Dice-K

TI__Mastermind 36495 points

Hello Dice-K,

That is how CC-CV charging works for lithium-ion chargers. First, current is regulated until the battery voltage is reached, then the battery voltage is regulated until termination. The CV phase, or taper phase, does not control the charge current. The taper current peak will depend on the programmed charge current.

As Wyatt said, you can use one charger for all the cells, but careful impedance balancing is required for equal charge of each battery.

The MAX17332 does not present parallel charging in the desired way. It uses two independent battery chargers for each battery pack. See Application Note here: https://www.analog.com/en/resources/technical-articles/parallel-battery-charging-with-usb-c-enhances-consumer-experience.html. It also has different features like being a gauge, protector, and charger.

Regards,

Mike Emanuel

Power management

Power management forum

BQ25616: Charging parallel cells