If your motorhome carries more than one solar panel, a technical question with real consequences comes up: do I wire them in series or in parallel? It isn't a minor detail: how you connect them affects output, especially when there is shade, and it affects which controller you need. Here we explain it clearly, without tying you in knots, so you understand the options. (For the installation itself, lean on a professional.)
The two ways of connecting them
- In series: they are connected one after another; the voltages add up and the current stays the same. More voltage, less current through the cable.
- In parallel: they are connected "as a block"; the current adds up and the voltage stays the same. More current, same voltage.
In both cases the total power is the same (the sum of the panels); what changes is how it is split between voltage and current, and how the array behaves in shade.
The key factor: shade
Here lies the most important practical difference for a camper, which moves around and parks in places with partial shade (a roof light, an aerial, a branch):
- In series, if one panel is shaded it can penalise the whole array (the chain suffers because of the shaded link).
- In parallel, a shaded panel affects the others less, and they carry on producing. It tends to be more tolerant of the partial shade typical of a camper.
The controller: MPPT, all but compulsory with several panels
With several panels (especially in series, at higher voltage), a good MPPT controller is practically essential in order to make use of the energy and work safely (see MPPT controller). MPPT also gives you more flexibility in how you wire the panels.
So what about my camper?
There is no single answer: it depends on your panels, your controller, the wiring and how you use it. As a guide, in many camper installations parallel is valued for its better tolerance of shade, while series can be worth it to cut losses over long cable runs. What matters is that the whole system (panels, wiring, controller and battery) is properly sized and fitted by someone who knows what they're doing (see the calculator and the panel guide).
In short
Wiring panels in series adds voltage and in parallel adds current; the key practical difference is that parallel usually copes better with the partial shade a camper meets, and with several panels an MPPT controller is all but compulsory. The step you can take today: if you're fitting several panels, consider parallel because of the shade and make sure you have a suitable MPPT; get advice so the whole system is sized and fitted properly. Combine it with the solar panel guide.