Solar Energy

Can we say the size of the Solar panel is one of the limitations in a solar practical experiment? For instance size or number of solar panels matters in real time installation, I believe 24 volts solar panel will charge 24 Volts battery in real time depending on the solar intensity, and I know that 48 Volts Solar panel (connected in series) will charge the 24 volts Battery faster than 24 Volts solar panel. Kindly share your thought on this.


  • Are you planning on using a solar charge controller?  If not, then sticking 24V across a 12V battery isn't going to end well.  Depending on the type of the battery, you could have boiling sulphuric acid or burning lithium to deal with.

    In general, big solar panels give more power than little ones, and two solar panels give more power than one.  That should be fairly obvious.  Solar panels could be connected in series for higher voltage, or in parallel for higher current.

    Don't assume that a 24V solar panel will actually produce 24V.  It will be less in cloudy conditions, and may be higher in bright sunlight.

  • Can you clarify your question ?  A particular level  of sunlight will give you a certain number of watts of electricity per square meter of solar  panel. How you care to slice those watts into volts and amps is really a convenience - a large installation may have series strings of panels totalling a few hundred volts to keep the current and wire sizes to a sensible level. For any given panel the there is a load "sweet spot" that gives maximum power, so some sort of electronic regulation is more or less essential to track changing light levels.

    However I am not sure if that goes any way to answer your question.


  • Thanks for the reply, but I did not mention 12V battery against 24V Solar panel. Sure Charge controller will be used to control the charging, I have done several Installation that still works for years. But this is about solar laboratory experiment, mentioned in my first sentence, the rest is just an example for more understanding of what I am talking about.

  • Thanks for your input, I am talking about Solar Lab experiment limitations.

  • what sort of lab experiment ? - is this for something like a training college to teach new folk how to use existing technology,  where really small even just a table top demonstration, would be fine,  or a proof of concept site to demonstrate cutting edge techniques on a sub-economic scale to see if it is worth scaling up ? (where anything from a single  house up to few hectares of panels may be 'small' )

    I am sort of just assuming you do not mean indoors - a clear line of sight to the sun is needed for best effect after all ;-)


  • Yes ! Size ( I mean wattage, Voc and Current) and Quantity of panels also matters for Charing the batteries But Charge controller has also major role for charging of batteries, MPPT AND PWM charge controller which one is best ? Answer is MPPT as it extract maximum power and provides better efficiency  as compared to PWM

    Lets assume that we have 150watt solar panels having Voc is 17 Volts and We are going to charge 24 V battery  in this case we use 150 Watts 2 Panels in series to make 34 volts to meet charging voltage requirement,  now its 34 v how we charge 24 battery so we will chose a MPPT Or PWM Charger with Input voltage Range Vin dc or Voc PV array should be greater than 34 Volts. This charge controller will charge 24v battery  

    `150 Watt 2 Panels in series 17voc each =34 volts Current will remain same  in series we call it PV array 1  ( now if you want to increase charging current) than you have to make an other array of Panels and connect them in parallel to get more current.

    So conclusion is,

    always choose panel size according to batteries voltage.

    always choose inverter and charger as per solar Panels Voc, current and battery charging current

    always choose solar panel quantity as per battery charging current requirement 

    Hope it clear your question.

  • My 12 volt solar panel charges the 12 volt battery uo to 14.5 volts but if I disconnect the panel its output voltage goes up to 21 volts when the sun is shining on it.  I fitted a regulator but it failed after a time so had to go back to direct charging. 

    If you can use the batteries charge every few weeks to run emergency lighting that would be ideal as overcharging the battery for extremely long periods will lead to loss of electrolyte although in my case that was over 4 years.

  • We had 10 solar panels installed in our garden at the end of last year. They are complemented by a 8.5kW battery and inverter in the garage. The panels generate up to 4.2kW corresponding to 21kW when it is sunny and about 10kW when cloudy. The battery has been topped up every day since February. The panels are connected in series.

    During the day the panels fill up the battery, feed the house and export to the grid. The house needs about 4.2kW per day. During the night the battery feeds the house but while doing that is also leaks energy to the grid and demands energy from the grid. Essentially the battery can't respond fast enough to changes in energy use and either leaks excess energy or demands missing energy for a short period. The changes in energy use are either around 10W or 100W when the fridge starts up.

    The inverter communicates with the supplier using wifi via our router. The link is done with a 2.4GHz Wifi dongle that didn't work with the router, which is 5GHz/2.4GHz, so I had to modify one of my RPI servers to connect to it at 2.4GHz.

    The solar panels are impacted by shading caused by clouds and they could be improved using micro-controllers.

    So by no means perfect. For the future I am considering adding another 10 panels or fitting a RidgeBlade to the roof and making use of wind throughout the day - but I am having trouble finding information and installers for that. Does anyone know anything about this?

    We installed solar panels because we had run out of ideas for saving energy in the home. We started in 2005 and have reduced it to half of what it was. This has saved us £15,000 over the years and that saving went to paying for the solar installation.

    I am in discussions with the Energy Saving Trust because they liked my innovative ideas for saving energy and I am in discussions with a councillor, helping them insulate their home. So it is good that I am retired.

  • A new problem has emerged with solar panel output during the recent hot spell of weather - apparently the output shrinks with temperature rise, It can be sunny but if the surface temp of the panel becomes too great, it's output falls away.

  • not new - its a feature of all semiconductors that the carrier mobility falls at higher temps - it is reversible, so will recover when it cools. The effect is not that dramatic on a well proportioned system considering that excess heat usually coincides with excess light as well. and the loss is less than 1% per degree rise  above 25C, so even if the panel is at an unlikely 50C, you might have lost 20-25% relative to the same panel cooled at that light level - so you still produce about 75-80%.  Amorphous thin film panels do better with about 1/4 % roll off per degree and are often specified  in hotter countries.