BQ25790: Dual USB Type-C Power Bank for 8-Cell Li-on Batteries with Solar Charging Capability

Hi SM_ENG,

Are the 8 cells configured as 1S8P up to 4S2P, then BQ25798 with TPS25751 reference design might be of interest: https://www.ti.com/tool/USB-PD-CHG-EVM-01. You would need 2 in parallel for dual USB ports.

If the configuration is >4S, then BQ25750 family with TPS25751 or TPS65994AD family might work.  

Regards,

Jeff

Thank you for your quick response and assistance! I wanted to clarify my requirements:

I have two 4S2P batteries that I need to charge simultaneously from one USB-C port.

a) If I were to use only one USB-C port, I was considering the BQ25750 charger family with the TPS25751, connecting the two 4S2P batteries in series. This setup would also allow the same port to charge external devices as a power bank.

However, how can I expand this setup to have two USB-C ports? Specifically:

• If a charging adapter is connected to one port, the batteries should charge from that port.
• If the adapter is connected to the other port, the batteries should charge from that port instead.
• If i connect external device like iphone to one of mentioned ports it uses USB C PD charging.

b) If I opt for two circuits of BQ25798 with TPS25751 to charge each 4S2P battery separately, I am uncertain how to configure the two USB-C ports to charge external devices from both batteries effectively.

For both solutions, I assume a host MCU would be needed to control the power paths. However, are there any more standalone solutions that could simplify the design?

I would greatly appreciate any guidance on this topic!

HI SM_ENG,

The TPS25751 has firmware controls either the BQ25798 or BQ25750.  It is my understanding that no MCU would be needed.  However,  I am looping in the  the USB-C team as they can better help with choosing between USB-C chips.   

Regards,

Jeff

Hi, 

SM_ENG said:

a) If I were to use only one USB-C port, I was considering the BQ25750 charger family with the TPS25751, connecting the two 4S2P batteries in series. This setup would also allow the same port to charge external devices as a power bank.

TPS25751 does not have integrated I2C support for BQ25750, however we do support BQ25756. Jeff can provide further details on these specific BQ parts if needed. 

SM_ENG said:

b) If I opt for two circuits of BQ25798 with TPS25751 to charge each 4S2P battery separately, I am uncertain how to configure the two USB-C ports to charge external devices from both batteries effectively.

Do you have block diagrams for both option A and option B? This will help us better understand the project requirement. 

SM_ENG said:

For both solutions, I assume a host MCU would be needed to control the power paths. However, are there any more standalone solutions that could simplify the design?

TPS25751 has integrated I2C control to configure BQ25798 based on the simple questionnaire through the TPS25751 GUI. Through the TPS25751 GUI you can set BQ25798 charge voltage, charge current, termination current and pre-charge current along with DPM settings for forward/charge mode. In operation, TPS25751 will configure BQ25798 OTG or charge mode depending on the negotiated PD contract, requiring no MCU to be involved with setting the proper voltage/current. 

Thanks and Regards,
Raymond Lin

Hello Raymond Lin, 

Thank you for your answers.
Let’s remove the barrel jack from the task and focus on two Type-C ports with sink/source functionality.

Please see the block diagram I’ve created.

• Option 1: The power bank is charged via one of the two Type-C PD ports using a Type-C PD power adapter.
• Option 2: The power bank charges other devices through the two Type-C PD ports.

Lets take for each USB-C port TPS25751 and BQ25798. 

1. Is it possible to charge the batteries from Charger A when a power adapter is plugged in, and vice versa, if the adapter is plugged into Port B?
2. Will the smartphone charge if the power adapter is connected to the Type-C Port A for charging the batteries, and the smartphone is connected to Type-C Port B?
3. How should we manage the situation where two 4S2P battery packs have different charge levels?

Hi SM_ENG,

Because the 4S2P packs are connected in parallel, they will self balance.  

Regards,

Jeff

Thank you. Only thinking what will happen if two Type-C power adapters will be plugged in to two Type-C ports at same time and will negotiate to charge the batteries. Is it possible to charge batteries using two BQ25756 with higher current?

Hello Jeff F, Thank you for the professional response. I hope this information will benefit not only me but also other community members.
I have one last question about simultaneous charging and discharging.
Are there any side effects or recommendations to consider if one BQ25756 charges the battery pack while another discharges it, for instance, when charging a smartphone at the same time?

Thanks Jeff F.