Any advantage for MPPT over PWM if panels are wired prallel?

[truscott]

I have two 120Watt panels which I intend to wire in parallel to offset any shading that my boom or wind gen may create, and am wondering if there is any advantage to be gained by swapping my existing PWM controller for an MPPT one?

All the reading and searching I have done seems to indicate that the main advantage is gained if the panels are wired in series, as this higher voltage can be better utilized. However once one of the panels is in shade, the whole array produces nothing!

Is my understanding correct?

Appreciate your comments.

Cheers, PT

 

[noelex]

There is a lot of debate between series and parallel connection with MPPT controllers. There is no definitive information, but the balance of evidence favours parallel connection in my view.

The gain from MPPT is only small in the order of 10-15% (although it will be greater in cold environments) and this sort of gain only applies if you install good quality MPPT controllers that can track well.

 

[RAI]

If you bought a MPPT controller and used if for one panel and kept the PWM controller for the other panel you might be able to measure the difference in performance.

 

[William_H]

Theoretically MPPT controller should give some improvement in output. However if you already have a pulse width controller and find that the charge you get suits your needs I don't think it would be worth buying MPPT type. On the other hand if you want to get every drop of solar current possible and not fit more panels due to space etc then MPPT should improve charge. (please tell us what improvement you get.
Likewise with an MPPT controller you can try parallel or series connection and see which one seems to be best under shaded conditions. good luck olewill

 

[JumbleDuck]

I have two 120Watt panels which I intend to wire in parallel to offset any shading that my boom or wind gen may create ...

Each panel will already have multiple strings of cells wired in parallel internally. As long as these strings run parallel to the boom, shading shouldn't be an issue.

 

[truscott]

Thanks to all for your responses.

If as Olewill says, it is possible to wire an MPPT up to two panels that are in parallel, then that 10-15% that Nolex suggests would be great. I have read that the MPPT controller gives better juice in lower light levels as well, so that would also be welcomed (if true).

I only have one set of wires leading from the gantry to the existing controller (which is situated a few inches from the battery locker), so not practical to try and run a side by side comparison (although if I hold on to the PWM controller, I may well try this just for curiosity sake).

If, as JumbleDuck says, that shading shouldn't be an issue due to the cells already having been wired up in parallel internally, why does everyone make such a big thing about choosing parallel over serial?

Cheers, PT

 

[JumbleDuck]

If, as JumbleDuck says, that shading shouldn't be an issue due to the cells already having been wired up in parallel internally, why does everyone make such a big thing about choosing parallel over serial?

I think it probably dates from the days of small, expensive panels with only a single string of cells inside. When I got my new panels (2 x 50W) I did tests in the garden with shading and concluded that only a hard transverse shadow across the full with of at least one cell in every fore-and-aft line of them caused problems.

From what I read, MPPT is better for big panels in dim light if you wire them in parallel. Otherwise there is not a great deal in it.

 

[vyv_cox]

My PWM controller seems to produce close to the theoretical maximum current for my 80 + 45 watt panels wired in parallel.

 

[charles_reed]

Only difference (apart from price) is that the PWM won't modulate down, as batteries go onto float.
To maximise charging capability of PV panels it's best to have them in series and through an MPPT controller. 48 volts is recommended for mine but even @ nominal 24v into a 12v system the MPPT controller is always @ 1v above system volts up to 14.4v in system.
Shading, of one or two cells, appears to have no effect on output on more modern panels - the KD Kyocera I have just shrug it off whilst the earlier KC did show a drop.

 

[GrahamM376]

If you bought a MPPT controller and used if for one panel and kept the PWM controller for the other panel you might be able to measure the difference in performance.

I have just that, with 2 domestic battery banks and 2 regs. 4 panels in parallel to split charge diode, feeding the 2 regs. Found the diode necessary to stop backfeed balancing banks overnight. The cheaper PWM puts more power in than the MPPT but, maybe that's a problem with makes, some being better than others.