BQ25700A, BQ25703A, BQ25710, BQ25713, BQ25713B Battery Charger Selection and Configurable Float Voltage

Hi There,

     Thanks for asking. Unfortunately none of them support floating configurable voltage. After CC/CV all the chargers listed need host to terminate charging.

    BQ2571X is the second generation of BQ2570X. They are designed for similar application, but BQ2571X series holds some improvement shown in the table. 

    From communication point of view, BQ25700A and BQ25710 are using SMbus, but others are using I2C.

    You are right BQ25713 and BQ25713B only hold different I2C address for dual charger application.

Regards

Thanks Shishuo,

Smart Charger

Does BQ25710 (SMBus version) count as one of the smart chargers mentioned in the BQ4050 and BQ40z50 datasheets on page 24?

"Reports the appropriate charging current needed for constant current charging and the appropriate charging voltage needed for constant voltage charging to a smart charger using SMBus broadcasts" https://www.ti.com/lit/ds/symlink/bq4050.pdf#page=24

Controllable Float Voltage

Do you have any 2S or 3S Lithium-Ion/Polymer chargers with OTG that do have a configurable float voltage?

Kind regards,

Hi There,

      Both BQ25700A and  BQ25710 can support CC or CV charging. Yes, they can be counted as smart chargers in the reference. 

      I assume the configurable floating voltage is used for lead acid battery. Our BQ2570X and BQ2571X series does support lead acid battery charging which allows flexibility to control the charge profile for different battery chemistries and configurations.

To achieve the profile you are referencing in that e2e post, you will need a host controller to implement the control side and program the charging current and charging voltage as well as disable charge when you reach various stages in the referenced charge profile.

You can utilize the integrated 8-bit ADC to monitor the battery voltage and the charge current and use your host controller with a simple state machine to make decisions based on this.

Thanks Shishuo,

Smart Charger

For smart charging, do we just need to put BQ25700A/BQ25710 and BQ4050/BQ40z50 on the same SMBus or are there more steps involved?

How do BQ4050/BQ40z50 know what voltage and current to negotiate with BQ25700A/BQ25710 in smart charging mode?

When the battery is charged and BQ25700A/BQ25710 turn off, will BQ4050/BQ40z50 turn the charger back on after the battery drains below a certain point?
e.g. the battery will continue draining while the product is connected to the charger.
Can we program the point where the charger will be turned back on?

Float Voltage

The programmable float voltage is for Lithium-Ion/Polymer.
I think I may have been using the wrong terminology.

We essentially want to be able to program the voltage and current setpoints used for CC and CV charging as well as the voltage the batteries will be held at after charging while the product is still connected to the charger.

This product will spend most of its life connected to the charger and we need to ensure that the batteries have a certain capacity at all times. While connected to the charger, some additional features are enabled which will drain more power, causing the batteries to relax and lose charge.

If we charge to 4.2V (per cell) and hold the batteries at 4.1V (per cell) after charging then we can guarantee that the capacity we need is there when the product is disconnected from the charger. (the aforementioned voltages would be different in our 2Sx6 or 3Sx6 system).

Kind regards,

Hi Dan,

     Thanks for your clarification.

     From your description, looks like you need the charger to terminate by itself after it is fully charged  and auto-recharge by itself when battery voltage falls below certain threshold.I would like to reiterate that BQ25700A/BQ25710 all need host to involve in terminating charge and auto-recharging. They don't support all these autonomous charging feature.

     I involve BQ4050/BQ40Z50 support team to help answer autonomous charger control questions.

Regards

The bq4050 and bq40z50 have JEITA tables that can show chargevoltage() register. There is a broadcast mode which can be used to broadcast these commands to a smart charger, but it cannot support multiple SMBus hosts.

Can BQ4050 and BQ25710 be on the same bus if the MCU is the host?

Kind regards,