2013-12-26

Experiments with supercaps - part 1

Hooray!

The long awaited supercaps arrived from China/Singapore....
It was a really good bargain - 5$ for 500F, 2.7V supercap!!!!
(http://www.shop-from-china.com/p-22352496639-South-Korea-three-and-SAMWHA-super-farad-capacitor-2.7V-500F-original-new-low-leakage.html)



They look worn. But I think they work. (this picture is from i-net)
OK - I have them, but now what to do? I don't have a charging circuit.
I could try my NPC1 battery charger, but it is too expensive, didn't want to damage it.

First experiment - I connected them to a cheap solar garden lamp.
I measured open circuit - about 2.1V on the battery ends - so I soldered the ultracap there.
(no picture sorry)

Started from 0.11V, in the end of the day it was - 0.85V.

When the night fell, the LED of the solar lamp worked, but was very dim, and after an hour did not emit any light @ 0.7V. In the end of the night it droped down to 0.65V

Second DAY!
Not very sunny most of the day. From 0.65V to 1.07V in the end. Perhaps this is the best for this set.
Started to give good light , but dropped to 0.86V for an hour and a half.
Next
If I didn't use LED, for 2 sunny days I could charge up to 1.7V. But it is enough only for a 2-3 hours of bright light.
Perhaps bad electronics for ultracap, or solar cell is not powerful enough, anyway it was just a try!


Second experiment - I charge them with 2 NiMH batteries!
For an hour I can reach 2V.
The following table gives the amount of energy in the supercapacitor, on certain voltage levels.
The energy is given for 500F capacitor, but the % full column is valid for any 2.7V capacitor:

Voltage (V)Energy (500F) Joules% full
0.102.500.14
0.2010.000.55
0.3022.501.23
0.4040.002.19
0.5062.503.43
0.6090.004.94
0.70122.506.72
0.80160.008.78
0.90202.5011.11
1.00250.0013.72
1.10302.5016.60
1.20360.0019.75
1.30422.5023.18
1.40490.0026.89
1.50562.5030.86
1.60640.0035.12
1.70722.5039.64
1.80810.0044.44
1.90902.5049.52
2.001,000.0054.87
2.101,102.5060.49
2.201,210.0066.39
2.301,322.5072.57
2.401,440.0079.01
2.501,562.5085.73
2.601,690.0092.73
2.701,822.50100.00

I bought some NCP1402 @ 3.3V from Pololu.
http://www.pololu.com/product/2114
This little board with NCP chip allows to have a stable 3.3V output voltage, while your capacitor
voltage drops from 2.7 to 0.3V. You see that at 0.3V we have about 1% charge, so with this circuit
we use 99% of the capacitor energy.
I have attached a standard 3.3V 20mA LED (I measured the voltage and the amperage to confirm).
Here are some pictures:




/part2/