BQ25504EVM-674: Charging a supercapacitor when Vin is low Vin=200mV

BEZAK

Part Number: BQ25504EVM-674

Hi,

I have connected a thermoelectric generator to bq25504EVM. In our application, the temperature difference is not a lot and when I measure Vin to bq25504 it is close to 200mV. I know bq25504EVM needs at least 330mV to start, so I connect another source just to start the system. I have a supercapacitor connected to VBAT and it has 0.4F and 4.5V. Related to our application I changed the OV-th=3.6V and UV-th=2.9V. If the supercap is charged to 3.4V I expect it to charge to 3.6V first but the cap does not charge and it actually discharges to 2.9V after 4-8min. This could be due to the low input voltage from the TEG. If the TEG gives above 250mV then the cap is charging or at least not discharging.

I thought the bq25504 is advertised to work at low input voltage. Any comments?

Thanks,

Bezak

over 7 years ago

0 Jing Zou over 7 years ago

TI__Mastermind 20570 points

Hello,

Could you please capture waveform on VIN, VSTOR, VBAT and SW?

0 BEZAK over 7 years ago in reply to Jing Zou

Intellectual 465 points

Hi,

Thanks for your reply. I could not provide this as the system is somewhere that we could not record the information. I only used a multimeter to measure different voltages.

Regards,

Bezak

0 ezhao over 7 years ago in reply to BEZAK

TI__Genius 10240 points

Bezak,

Is the problem solved? It is very tough to debug without waveform. You can post a new thread when you get access to the system.

0 BEZAK over 7 years ago in reply to ezhao

Intellectual 465 points

Hi,

Yes, problem is solved by increasing the number of input sources.

Regards,
Bezak

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BQ25504EVM-674: Charging a supercapacitor when Vin is low Vin=200mV