#142544  by Andrew_NZ
 Sun Jul 08, 2018 8:05 pm
I am planning my solar setup and would love some advice. I have limited roofspace but can fit 2 x 150 watt panels. It is a Hiace van so cable runs will be short and one panel may get some shading so I am planning on wiring in parallel and keeping at 12volt

My questions are:

Should I use PWM or MPPT? At present think that MPPT is the best option, but there are some suggestion that PWM for 'small' systems is negligible difference. Thoughts?

Should I have one or two charge controllers? At present I think just one but some suggest two controllers will optimise each panel. Some suggest two controllers will fight each other, but some say connecting each to a different battery will be ok (I have 2 x110Ahr). I am leaning towards one controller.

If in parallel should I join the panels in a junction box on the roof, or run both panels down and join at the controller. I have a good sized hole in the roof, cable run is short, I am not sure pros and cons. I guess there should be identical cable length for both or is that not important?

What fun learning all of this :-)

 #142545  by Andycap
 Sun Jul 08, 2018 8:23 pm
Hi,had both sorts of controllers .One MPPT is the way to go ,the differance in the amount of power they harness is massive .Cloudy ,wet day ,allmost dark , and still producing power .
 #142549  by Neddy
 Sun Jul 08, 2018 9:57 pm
If you only have room for 2 x 150 watt panels, it is important that you get as much energy as possible from those two panels.

“One panel may get some shading so I am planning on wiring in parallel”
Don’t do that. Here’s why. Since one panel may be shaded while the other is not, their outputs will be different, with different Maximum Power Points. To maximize their outputs, each panel needs to be run at its individual MPP. This necessitates their having separate controllers. If the panels are simply paralleled, a single MPPT controller is unable to run both panels at their optimum voltage and can only select a compromise value - one that will be too high for one panel and too low for the other. So with a single controller you end up with neither panel being run at its Maximum Power Point, while with separate controllers, each panel is run at its respective MPP, maximising the output of both panels.

“... and keeping at 12 volt”
Using "18 volt" panels rather than higher voltage? Good idea. The wider the "gap" between panel voltage and battery voltage, the lower the MPPT efficiency.

“Should I use PWM or MPPT? At present think that MPPT is the best option”.
It is.

“There is some suggestion that with 'small' systems there is negligible difference.”
The smaller the system, the smaller the gain MPPT delivers. With a 300W system like yours, MPPT controllers give a significant advantage.

Should I have one or two charge controllers? At present I think just one but some suggest two controllers will optimise each panel.
They will. See above.

“Some suggest two controllers will fight each other”
Nonsense. With both controllers set to the same parameters, they have the same objectives and play by the same rules.

“Some say connecting each to a different battery will be OK (I have 2 x110Ahr).”
Don’t forget that the main objective here is to charge your House battery – so you want the output of both panels primarily directed there.

“I am leaning towards one controller.”
Two would deliver you more power, especially since you know that one of the panels is subject to shading. It is also good to have some degree of redundancy built into your solar setup.

 #142557  by mattn
 Mon Jul 09, 2018 9:37 am
:TU Neville - As always
 #142663  by Andrew_NZ
 Thu Jul 12, 2018 6:08 pm
Neville thank you, I have learnt so much from your many posts, and your answers.
I now have two MPPT chargers on my shopping list, so my attention is turning to what size and what type!

Each solar panel is 150W (9.1A short circuit current, 8.33A current at Pmax) so on the surface a pair of 10A MPPT may suffice?
But when the battery is low, would the 150W of solar energy be converted by MPPT to 13v and 11.53A needing a 15A+ MPPT?
I am inclined to go for 15A or 20A (depending on brand) but interested in knowing why that sizing is right

MPPT & MONITOR: My wish list is
* Good quality and reliable
* Reasonable price
* two MPPT's hidden in a cupboard
* screen(s) mounted on wall displaying MPPT information
* battery shunt and monitor also neatly mounted on wall

Any suggestions to MPPT/screens brands and models?
Are there any cost-effective monitors/screens that could display MPPT and battery information on a single screen or am I most likely to need three screens?

Andrew P
 #142675  by Neddy
 Fri Jul 13, 2018 11:55 am
Manufacturers of solar controllers specify the maximum solar panel input for each of their controllers. For most 10 amp controllers this is about 130 Watts. Your 150 Watt panels would need 15 Amp controllers, or better.
I wonder if your proposed "multiscreen" monitoring system might amount to overkill, providing a lot more information than you really need. A Battery Monitor should provide most all important info, particularly the "Charge %" of your House battery. Your new solar controllers may well provide info such as Volts/Amps In/Out but this will seldom be of interest and your controllers can be hidden away as you propose. It is good to have the Battery Monitor in a prominent position though. Models that show multiple parameters (simultaneously) are available - maybe one of those would suit your needs. What parameters do you want to keep an especially close eye on?

 #142692  by Andrew_NZ
 Fri Jul 13, 2018 6:01 pm
Thanks Neville, I think you right that I just have a battery monitor on display (I will do some reading and maybe another thread about battery monitors!)
For the MPPT I am considering a few although quality and reliability important to me

Victon Smart Solar (https://victronenergy.co.nz/products/sm ... 12-24v-15a)
  • no screen at all thats a downside
    But bluetooth so i can view on my phone
    I like the datalog
    Phone app easy to configure and view performance and history
    approx $220 ea
Epever Tracer (https://aasolar.co.nz/EP%20Solar%20Controllers.html)
  • seem to be widely used
    could get remote panel/bluetooth (has anyone got)
    approx $120-$150
Unknown Brand (https://www.aliexpress.com/item/Hot-Sel ... 2e0e960A0W)
  • Display
    I saw someone recommended in the forum
    Approx $100
There are others so keen to get feedback and experiences

Andrew P
 #142697  by Nut17
 Fri Jul 13, 2018 7:32 pm
The unknown brand from aliexpress is commonly sold under the "SRNE" brand name. The advantage over the equivalent Tracer model is that a separate remote display is not necessary for programming.
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