BQ25505 Solar with LiPo

Vlad Lazar

Other Parts Discussed in Thread: BQ25505

Hello,

I am trying to figure out if the BQ25505 eval board is suitable to be used with solar panels and LiPo batteries.

I might have misunderstood the way the IC works, but isn't the 2V undervoltage protection a bit low for LiPO (my battery has something like 2.8V minimal voltage)?

Do I just connect my load on V_STOR and the LiPo on BAT_SEC or follow the example from the section 3.2.4 and connect the load in parallel with the battery ?

Best regards,

Vlad

over 12 years ago

0 Jeff F over 12 years ago

TI__Guru**** 180286 points

If the 2V integrated VBAT_UV threshold is too low, then I suggest adding a PFET in series between the VBAT_SEC pin and the battery. You can set the VBAT_OK lower threshold to 2.8V and use the /VB_SEC_ON pin to drive the PFET. Unless there are large load transients, I suggest connecting your sysem load to VSTOR.

0 Vlad Lazar over 12 years ago in reply to Jeff F

Prodigy 50 points

Thanks for the info.

0 Vlad Lazar over 12 years ago in reply to Jeff F

Prodigy 50 points

Hello,

I had one more question: Does this board manage the charging of LiPo battery elements (constant current/ constant voltage regions), or I would have to use an external controller?

Best regards,

Vlad

0 Jeff F over 12 years ago in reply to Vlad Lazar

TI__Guru**** 180286 points

The bq255xx family only monitors battery voltage. With a HiZ harvesting source, it is expected that the charge current will be delivered in bursts, as the bq255xx boost converter pulls current from the source only until it starts to collapse. Therefore constant current charging is not possible.

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BQ25505 Solar with LiPo