Hi,
I would like some help with the bq25504 energy harvester. I would like it to charge a small LI-PO battery (fullriver 20mAh 20C max discharge rate) with a solar cell (KXOB22-4x3, Voc= 1.89V, 15mah). I prepare a board with the circuitry following the datasheet (a mix between figures 2 and 3) and evk user’s guide. These are the resistors (megaohms) used to control the different voltage thresholds (megaohms):
UV: Ruv2=6.19 Ruv1=3.83 to give a voltage of 3.27V
OV: Rov2=5.62 Rov1=4.42 to give a voltage of 4.25V
Ok: Rok1=3.32 Rok20=6.19 Rok3=0.499 to give a voltage o 3,58V
Mppt Roc2=15 Roc1=4.42
The inductor used is Bourns SRU3028-220Y (22microH, tolerance 30%, DCR 270mohms, 0.6 A,SRF 15Mhz)
When I connect the solar cell and battery and the later did not charge(I leave for an hour at direct sunlight). I try a cold start to check the circuit and when the cell reach 1.8V, voltage at the Cstor quickly increase to reach 4.19V so I suppose that all is correct in board.
Which could be the cause of the fail to charge the battery?
In case I don’t use the Batok signal , should I leave pin 11 unconnected or connected to ground? In such case could I leave pin 10 and pin 9 unconnected or connected to ground?
Thank you in advance
All the best