In this article we will learn why you should not connect different solar panels, but if you have to, we will show you how to connect solar panel in series.
1) Apart from rated power, each panel has its power degrade percentage.
Therefore, you should expect different output degrade of any solar panel over time. Moreover, the degradation stated in the technical specs does not always coincide with what is stated on a panel’s nameplate. Therefore, it is not easy to find an exact panel match from different solar vendors.
‘Exact match’ means both similar rating and similar rating degradation.For panels connected in a series, voltage is additive while current is the same, provided all the panels are of equal current rating. If, among the panels connected in a series, there is a panel with a rated current lower than the rated current of the others, it will drag down the current that is passing through all of the remaining panels.
Therefore, each of the remaining panels (of a higher current rating) will underperform: it will produce current (and therefore power) lower than the current stated on its nameplate. In other words, if two dissimilar modules are wired in a series, the voltage is still additive, but the current will be only slightly greater than the current produced by the panel with the lowest current output in the series string. And this is not how you want to connect solar panel in series !
2) For panels connected in parallel, the current is additive while the voltage is the same. If there is a panel among the panels connected in parallel with rated voltage lower than the rated voltage of the others, it will drag down the voltage of all the remaining panels.
Therefore, each of the remaining panels (of a higher voltage rating) will underperform: it will produce a voltage (and therefore power) that is lower than the voltage stated on its nameplate.
3) Mixing solar panels with different electrical characteristics is not recommended if you use an MPPT charge controller. Different wattages make it impossible for the controller to find the optimal operating voltage and current since they are different for each panel type.
The solution is simple: utilize panels that have electrical characteristics similar to the original panels.
In order to minimize the losses when connecting different solar panels:
- Connect in series only panels of the same brand and manufacturing series.
- Connect in a series only panels of different brands and of the same current – this is your second option, if you cannot find panels of the same brand for any reason.
- Connect in parallel panels of the same brand/ manufacturing series and of the same voltage.
- Connect in parallel panels of different brands and of the same voltage — this is your second option, if you cannot find panels of the same brand for whatever reason.
- Connecting different solar panels with the same array is not recommended, since as a result the voltage or the current might be reduced. Therefore, if you are planning to use dissimilar panels, try to use ones of comparable stated voltage and current.
- As a last resort, if you, for whatever reason, have to use solar panels of different series from the same manufacturer or from a different manufacturer, please consider using a separate charge controller or inverter, depending on the solar panel system type you are installing. The higher yield of the solar panels will justify quite quickly all the money spent on the additional hardware.