BQ24170: How to handle LiPo with different charging and discharging connectors

Konstantinos Tsoumanis

Part Number: BQ24170
Other Parts Discussed in Thread: BQ29209, BQ29200

Hello,

I am interested in the BQ24170 charging IC. However, I would like to use a LiPo battery that has two different connectors, the first one for charging and the second one for discharging. I was wondering if I could use the BQ24170 IC and connect the battery through its charging connector, but connect the drain of the BATFET to the discharging connector of the battery. Would this work?

Also, could you suggest me of a balance IC that I could use with the BQ24170 for 2-cell LiPos?

Thank you in advance.

Best regards,

Konstantinos.

over 6 years ago

0 Jeff F over 6 years ago

TI__Guru**** 165886 points

Hi Konstantinos,

Can you provide the battery part number? I would like to understand it better. Based on your explanation, it appears that your suggestion would work as the external battery FET is only for discharge and the SRN pin is used to sense battery voltage and charge current. Regarding balancing ICs, I am not as familiar with those products. Based on a quick web search, it appears that the BQ29200 or BQ29209 might work for you application.

0 Konstantinos Tsoumanis over 6 years ago in reply to Jeff F

Prodigy 80 points

Hi Jeff,

Thank you for your reply.
Yes, sure. I am interested in using batteries like the following: hobbyking.com/.../turnigy-battery-nano-tech-3000mah-2s-25-50c-lipo-pack-xt-60.html .

Regards,
Konstantinos.

0 Konstantinos Tsoumanis over 6 years ago in reply to Konstantinos Tsoumanis

Prodigy 80 points

Hi Jeff,

So, would it be ok to use the BQ24170 IC as a charger for my battery?

Also, do I need to use any more protection ICs on top of the BQ24170 and BQ29209?

Regards,
Konstantinos.

0 Jeff F over 6 years ago in reply to Konstantinos Tsoumanis

TI__Guru**** 165886 points

Hi Konstantinos,

Yes, the BQ24170 should work for your application. Your battery is called a "battery pack" as opposed to a cell which typically means it has its own should internal protection.

0 Konstantinos Tsoumanis over 6 years ago in reply to Jeff F

Prodigy 80 points

Thank you very much Jeff.

A last question regarding my design. Would it be ok to increase the maximum system load current that can be supplied by the adapter? I mean I would like to have the possibility to supply up to 6A to my system load. So, lets say a maximum of 6A and not 4A as stated for the charger. If I replace the Q1 and Q2 transistors with two transistors that can accept such an amount of current, would it be ok? Also, the Q3 transistor for supplying current through my battery.
Is there anything I should pay attention to regarding the RAC between the ACN and ACP pins for such amounts of current?

Thank you in advance,
Konstantinos.

0 Jeff F over 6 years ago in reply to Konstantinos Tsoumanis

TI__Guru**** 165886 points

Hi Konstantinos,

The 4-A rating is for the internal buck converter FETs. As long as you do not try to set 4A charge current, and resize the AC FETs and components, I see no issue. We have not tested the IC with RAC less than 10mohm so I would not lower it below 10mohm.

Best regards,
Jeff

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BQ24170: How to handle LiPo with different charging and discharging connectors