I have bought recently a voltage / current electronic gauge,similar to the one below. The objective was to check simply the charging performance online.

So the first conclusion is: however the nominal current of panel is 1.74 A, on 9th of Feb with rather cloudy sky above Warsaw  I can not reach higher value than 0.7A. There are two same 30W panels connected at the moment, so we can roughly calculate about 1.4A max charging current, around 18W max performance.

18W from 60W in total --> 30% of nominal capacity. I expect much lower values with really cloudy sky.

Of course with clear sky the value could be higher, but as it is rather standard weather at the moment we can assume that the PV systems work with about 50% of capacity.

If you have any other observations from your PV installations, please share in comments.

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.

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.


    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.


    February 2015
    December 2014


    Renewable Energy