# efficiency Pv in series with capacitor to charge a battery or power DC motor

2 Posts
Jul 1, 2010 04:50 pm
efficiency Pv in series with capacitor to charge a battery or power DC motor

What happens to amps, when charging a battery or powering a motor..
from a 4V circuit of solar cells and a capacitor in series.
(capacitor low voltage cutoff point @ 1.5V)

example:

3 solar cells (0.5-.58v) 1.5v @ 3.5 amps

1 ultra capacitor 2.5v 310F
Capacitance (F) - 310
Rated Voltage (V) - 2.5
ESR, DC (mohm) - 2.8
ESR 1kHz (mohm) - 1.1
lc (mA) - 0.45
Max. current (A), 1 sec - 390

battery : 3.3V 2300mah Internal impedance: (1kHz AC) 8 mΩ
(low voltage cutoff is 2.8V) / (charge cutoff 3.65v)

Motor (any) : 4v 2A DC ...

questions:

does the capacitor override the solar cells, and provide all the amps ?

does the capacitor bring down the solar cells somehow ?

Do the two power sources compliment each other, and share the load / evenly ?

thanks for any thoughts or comments to help me understand the circuit.

184 Posts
Jul 5, 2010 01:33 pm
Re: efficiency Pv in series with capacitor to charge a battery or power DC motor

I'm confused.  When I was in school I learned that capacitors (in series) do not pass DC current.  Can someone enlighten me please?

2 Posts
Jul 5, 2010 06:50 pm
Re: efficiency Pv in series with capacitor to charge a battery or power DC motor

Hi John..
Yes, you are correct.. caps do not pass current.. the farads of the series will be divided by the number of caps..

But, Im not trying to pass the capacitor's current, Im trying to only use the caps voltage combined with a small number of solar cells.

Ive since been trying something different, using 1 LiFePO4 3.3v in series with 3 solar cell array.. to charge another 3.3v LiFePO4 battery cell which is almost depleted ofcourse...
seems to be working !!

started with a depleted 2.8V LiFePO4 cell and a 3.2v cell
3 cell solar array in series..

after rotating the position of the two battery cells twice, the voltages are now:
3.23v & 3.05v..
amps approx. 2.4a - 3a charging

I wanted to use the three solar cells in parallel in series with the 3.3v battery cell to charge another battery cell.. but the output amps from the solar cells does not add up
3a +3a +3a
my anmeter only shows approx. 3.6a

next will try 6 solar cells array in series in series with battery cell.

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