Given the roof space (which we don't have) I would leave the existing one, complete, exactly as it is and fit whatever i could fit on the roof as a separate system.
Most of the panels used on MHs are all the same voltage so you can wire then in parallel without problem. If you want to be absolutely sure just count the number of cells, which are the rectangular or octagonal shapes which make up the panel. Panels with the same number of cells will have the same voltage.
As long as the controller (MPPT type of course) has a lithium battery profile in the settings it will be future proof. To install lithium later you will probably need to change the mains charger and fit a battery to battery charger because the vehicle system will be designed for lead acid. This all gets expensive hence my suggestion of a suck it and see approach.
The controller,old and new, would just live together charging the battery bank side by side----- it might not be exact enough to give the ultimate charging for the fanatics!! But it will work.
Most panels are around 20 volts but a slight mismatch won't make any difference as the controller brings it to a nominal 12v.
Yes although as nicholsong suggests you could connect a second panel to its own controller. This has advantages because it means if one panel is shaded the other will continue to produce maximum power - but it will mean running extra cables. It also assumes the existing controller is an efficient MPPT type which you can't assume - converters have been known to cut corners!
Yes but, doing it in series you don't increase the watts, only the voltage so you have 36v but only 80watts from 3 x 80watt panels
Yes, that's what I did as the cables in mine were a bit thin. But it doesn't work well if the panels are different sizes as the smaller panel will restrict the maximum current flow.
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Correct. But you must make sure the controller can handle the higher voltage. Many of the smaller systems have a controller with a voltage limit of around 35v. Two panels in series would exceed that voltage. There's plenty of controllers that will handle the voltage, but you have to check the specs.
The power depends mostly on the total area of the cells. In larger panels each cell is larger than the cells of smaller panels. The cable thickness is decided by the current flow (amps) rather than the voltage. If you really really want to not change the wiring, you could wire two panels in series. This means the voltages add but the current (amps) stays the same, so the wire thickness can stay the same.
But when those 36v go through your mppt it will give you the same power to the battery---- it is capable of turning volts and watts to the correct power to charge battery. That is one reason to insist on mppt, it can normally handle a wider range of power.
A '12 Volt' panel has a maximum voltage of 18 to 26 volts. A controller needs about 5V more than the battery voltage to convert the power. It's called '12 Volt' because it's not enough for 24 volt batteries. Larger panels have a voltage of 35 to 45 volts, suitable for 24V batteries. But with a suitable controller they are fine for 12V batteries too.
Do you mean join them individually to the existing cable?
All the positives connected together, all the negatives connected together - that's parallel.
See my edited post, I pressed 'post reply' before I'd finished so just shortened/reworded it instead ... you 'nabbed' it before I'd done so.
Odd sized panels aren't a problem.
Cables should have the size embossed on them. If not(cable may need replacement) there are online calculators to work out the size of cable required related to panel output and length of cable required to reach the controller.
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