Part Number:BQ25504
E2E Community,
I am evaluating the bq25504 PMIC for my design due to the low voltage characteristics as I would like to harvest light indoors...and outdoors. Ideally I want to harvest any and all light.
My first problem is getting over the minimum voltage hump of 330mV in low light. I am using the IXYS SLMD121H08L panels with a rated Open Circuit Voltage of 5.04 V. Indoors, with two panels in series,the Open Circuit Voltage can be as low as 1.0 V. If I then plug into a load the voltage drops dramatically, as expected of a PV cell. In one experiment I have plugged the two panels into the Sparkfun LiPower converter (which uses the TI TPS61200) which is looking for a 0.5 V startup voltage. When I plug my 1.0 V (Open Circuit) panel configuration the voltage drops down to 0.3 V and nothing is converted. If I had an MPPT then I should be at around 80% (ballpark estimate for the MPP) which would put me at 0.8 V, enough for the minimum voltage to fire up the PMIC. Does the bq25504 MPPT work immediately at startup?
My second problem is too much voltage under direct sunlight. The two panels in series can give me up to 11.5 V (Open Circuit, measured in Phoenix AZ direct sunlight). If I apply the rough calculation for MPPT of 80% that leaves me with 9.2 V which is too high for the bq25504. Can I program the MPPT such that it is limited to the bq25504 absolute max VIN of 5.5 V, or 5V to be safe?
Panel Datasheet: http://ixapps.ixys.com/DataSheet/SLMD121H08L_Nov16.pdf
Any insight is appreciated!
Thanks,
Jered