Recently doing something with cables and the stuff I accidentally connected plus and minus cables and burned one of fuses. I would not be a big deal I had noticed that immediately. As I had not, system started to work with only one of three batteries, the smallest one, 12 Ah. The result was that having light in the kitchen on I had 10 V on the installation. The next morning with the sky full of clouds ( so poor charging) my green diode was shining very bright light ( few hours later it was 10 V).

I started to looking for the reason and and found the blown fuse.  After replacement system works normally.



It was quite good experience to see the performance of system with drastically oversized PV cells comparing to battery capacity. Charging / discharging goes very quickly, system is not stable enough. As I found recommendations, batteries capacity should be twice as much as PV capacity e.g. 60 W PV, 120 Ah. I have bit less, till summer time it is fine, then some amount o energy I can not accumulate anymore.



 
 
On Coursera.org you can find course dedicated to PV. At the moment there is no open session, however in my opinion it is worth to follow the course,  if you are interested in getting more knowledge about PV. The course is in french, so that can be additional obstacle. I could not find anything in english.

Small Scale PV performance update:

In Warsaw cludy again, voltage below 12 V, during whole day the light in the kitchen is on ( supplied by PV) so batteries do not have easy life.
 
 
I would like to show you my simple voltage level that I use in my system.

I used a resistor 1 kOhm,  green LED and Zener diode 10 V. Wiring diagram below:
As you see, the main principle based on Zener diode, which stays off until Zener voltage does not across its Zener voltage. In fact, in this case you need to add also an activating voltage of LED diode ( about 2 V for green colour). So ultimately you get minimum voltage level about 12 V to start LED lightening. Resistor 1 kOhm was taken experimentally. You can try with higher value, but I would not suggest to go down much lower than 1 k, as if above 12 V in installation the current value can make your diodes warm.


So, finally you install your indicator on one of your 12 V battery ( capacity does not matter) and from now on you are always aware if the level on your battery is above or below secure level.

BTW, I am going to test also red LED. As it requires lower voltage to light ( 1.6 V) it is possible to build up about 11.5 V indicator, having the same Zener diode.


 

Clouds

01/12/2014

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Two weeks of clouds

For last two weeks there were practically no sun . Due to that, the voltage in the system was below 12 V all the time. As for the moment main energy receiver is LED light in my kitchen ( about 12 W), it is still OK. However, if I wanted to run my laptop using 12 V charger, we can say about only 30 -45 minutes of work.

Charging current right now ( 11.30 Warsaw time)  - about 160mA ( nominal cells power - 60 W). That gives us about 1.6 W. Not a lot if you think about continuous domestic consumption supply.

Conclusion: No sun, no fun :) at least in terms of  PV
 

    About me

    Hi, I am Michal. My idea was to start my own small scale PV system in my flat. I live in Poland, Warsaw district.

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