Like any system, the components of a photovoltaic installation must be related to each other. We cannot use a large number of plates or a high-powered inverter to charge batteries that are too small, because if we do not keep a proportional relationship, the useful life of the batteries would be shortened and the efficiency of the installation would be reduced.
Number of solar panels required
The number of solar panels that we will need in the installation will be given by the existing consumption in it. That is to say, if the installation is going to be used during the whole year, we should cover the average consumption of a day in December, since it is the time of the year that we will have less solar hours. If the installation is going to be installed in a house of occasional use, for summer and some weekend, we will have to cover the consumption for a day average between September and October.
To calculate the number of plates they have to bear in mind the hours of solar peak (HSP) of the location, the technical characteristics of the plates to installing and the losses that we could have in the installation. You can use our consumption calculator and see the solar kit that best suits your needs to know the solar production that would have your installation and the power and number of plates needed.
Important: The battery charge current should not exceed 10% of the battery capacity in C10. And never exceed 20% so we will design the solar generator so that the charging current does not exceed that 10%. We must not over-dimension the installation on installed panels, and allow the solar regulator to charge with currents higher than that 10%.
Capacity of the batteries
The energy stored in the batteries will not give the autonomy that the installation will have in case of not having solar energy. As we should not discharge them more than 50% what we will do is multiply the daily consumption by 2, so that the capacity of the same one is thus the double, with this we would have one day of autonomy, and we will multiply by the number of days of autonomy that are wished to obtain the necessary capacity in batteries.
Batteries are usually designed for 3-4 days of autonomy, although this depends on the area where the installation is going to be placed, which would make us have to multiply the daily capacity by the number of days to have the necessary autonomy.
For example: A consumption of 2000Wh/day x6 = 12.000Wh/day
If the battery is 12V: 12.000Wh /12V = 1.000Ah of battery at 12V (consisting of: 1 battery of 12V and 1.000Ah; or 2 batteries of 6V and 1.000Ah in series; or 6 batteries of 2V and 1.000Ah connected in series).
If the battery is 24V: 12.000Wh / 24V = 500Ah battery at 24V (formed by: 2 batteries of 12V and 500Ah connected in series; or 4 batteries of 6V and 500Ah connected in series; or 12 batteries of 2V and 500Ah connected in series).
If the battery is 48V: 12.000Wh / 48V = 250Ah of battery at 48V: 4 12V and 250Ah batteries connected in series; or 8 6V and 250Ah batteries connected in series; or 24 2V and 250Ah batteries connected in series).
Conclusion: If we install batteries with lower capacities than those needed, we take them almost to their full depth of discharge, which shortens their life and it is easy to cause an early death of the batteries.