HTCC-AB01 Constant Voltage over Vs-GND?

#1

Hello, i’m trying out the cubcell board (HTCC-AB01) with two small solar cell panels, they are just outside the requriments for connecting to Vs (Voc is about 4 Volts). So I tested with both connecting them in series and in parallell for comparing the performance. However it turned out that when connected to the board even when in series the voltage over the cells became 4 V. Also the current where slightly higher when in series.

TL;DR Solar cells in series Voc =8.3 jumps to 4.1 V after connecting to Vs
Do you have any suggestions why it behaves like that?

#2

hi,
Did you get 4.1V at the position shown in the figure below?

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图片.png1016×479 14.3 KB

If so, it is normal. Because the maximum output voltage of the BAT pin of the TP4054 is 4.2V

please refer the TP4054 datasheet:


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图片.png884×637 102 KB

#3

I measured directly on Vs, which would be Vcc pin on the TP4054 right? I saw the datasheet for the TP4054 before I posted and also noticed the section you marked, can it affect the input someway?

It might also be that simple it’s the properties of the solar cells and that the load actually lowers the solarcell voltage exactly that much, but since it was almost the same voltage when connecting parallell and in series I’m not totally convinced. However this is not a big issue for me, I’m just trying to get a better understanding on how everything works.