BQ77915: Protection in IC - to take care of Charging Mosfet failure (MOSFET failed and shorted internally )

Anil Sudhakaran

Part Number: BQ77915
Other Parts Discussed in Thread: BQ7718

Hi,

In our BMS, we had a few failures in which charging MOSFET failed . Unfortunately when failed , MOSFET got shorted internally and charging continued. This can cause cells to over charge.

Charger has a maximum voltage limit, which will help to some extent. But if the all the cells are not balanced due to aging, there is a chance that a few cells will go to high voltages.

Any suggestion to protect cells from overcharging in such cases ?

(I know Mosfet selection/design should ensure Mosfet will not fail, just trying to look for a fail safe option).

Regards,

Anil

over 3 years ago

0 Luis H. S. over 3 years ago

TI__Mastermind 42070 points

Hello Anil,

If you are concerned about the primary protector failing, a redundant secondary protector can be used to protect the batteries in case the main protector fails. Secondary protectors usually blow a fuse to protect the cells and device. For an OV secondary protector to use, I would recommend the BQ7718. check our protector catalogs and see which would work best.

Best Regards,

Luis Hernandez Salomon

0 Anil Sudhakaran over 3 years ago in reply to Luis H. S.

Expert 1125 points

Thanks Luis for the details. BQ7718 will do our Job.

Our charging and Discharging MOSFETs are rated at 100Amp, 100V.

Can you recommend efuse or some other solution in 100 amp, Volts range.?

Efuse that I could find from TI are in very low current and voltage rating compared to what we need.

Regards,

Anil

0 Luis H. S. over 3 years ago in reply to Anil Sudhakaran

TI__Mastermind 42070 points

Hello Anil,

I do not know too much about the fuses. We usually use Dexerial footprints in our EVMs, however these are usually unpopulated.

This e2e thread may be helpful for fuse functionality: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1058822/bq76952-fuse-pin-functionality

Best Regards,

Luis Hernandez Salomon

0 Anil Sudhakaran over 3 years ago in reply to Luis H. S.

Expert 1125 points

Thanks Luis.

"Resolving" this thread.

Regards,

Anil

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BQ77915: Protection in IC - to take care of Charging Mosfet failure (MOSFET failed and shorted internally )