Three solar panels, connect in series or parallel?

[MtB]

Starcoaster now has three 120w solar panels on the roof of Sringy and today I'm planning to connect them up to the domestic battery bank (comprising three 12v leisure batteries) via a Tracer 30A MPPT controller. I can't decide whether to connect the panels in series or parallel.

 

In parallel I suspect the effects of any shadowing on the panels will be minimised, but bigger than normal 6mm cables might be needed. What does the team think?

 

And are there any other considerations I've overlooked?

 

Many thanks.

 

MtB

 

[matty40s]

6mm will be fine mike.

I would wire them in series meself, to make more use of the mppt function using the higher voltages.this would also mean you only really need 4mm. Depends on the shading expected I suppose.

I have plenty if you need some.

[smileypete]

Series should be fine, as long as the panels are identical and the total series voltage doesn't exceed the Tracers max input voltage under any conditions, even at no load and low panel temperatures.

 

Panels usually have bypass diodes in the junction boxes that mitigate the shading problem, if not then putting in parallel isn't so bad, coz the Tracer is a little more efficient at lower solar voltages.

 

cheers, Pete.

~smpt~

Edited July 14, 2013 by smileypete

[MtB]

Ok fanx, series it is then...

 

I have a fair bit of cable in stock myself too Matty, hopefully enough and the right connectors etc. Thanks for the offer though, I'll call you if I need anything more.

 

Cheers!

MtB

[KJT]

I had the same issue back in January when I had four 100 watt panels fitted to a Tracer 30amp MPPT controller. The suppliers of the Tracer, Sunshine Solar, advised me to fit them in parallel as they will be less affected by partial shading. Another factor in my installation is that at times the four panels have a different angle presented to the sun as they form the 'lids' of a top box and the effect of the resulting differing panel performance would be less if wired in parallel.

 

Ken

[MtB]

Thanks boys and girls and Matty

 

I've wired them in series and it seems to work fine (as expected).

 

 

MtB

[Starcoaster]

MB may be missing out one important "oopsie" (that wasn't the word I used at the time) though...

 

Ooooh, controller. Shiny! Already obsessed with the readings...

Epical. Free electric! MB is the best boy EVAR.

Edited July 15, 2013 by Starcoaster

[MtB]

MB may be missing out one important "oopsie" (that wasn't the word I used at the time) though...

 

Oh yes.

 

When connecting the third out of three domestic batteries in parallel, it is bettter connect it the correct way around. I initially connected it back to front (DUH) and shower of sparks was very pretty...

 

But the screaming seemed to go on for an awful a lot longer....

 

MtB

[Starcoaster]

Sparks?! HUGE bang, cloud of smoke and MB not moving or reacting fast enough for me not to be sure he hadn't electrocuted himself!

[MtB]

Sparks?! HUGE bang, cloud of smoke and MB not moving or reacting fast enough for me not to be sure he hadn't electrocuted himself!

 

I wasn't especially bovvered and saw no need to 'react' fast. It was clear what had happened and there was nuffern to be worried about.

 

After 0.3 seconds I was more annoyed to have spoiled a brand new £5 battery terminal clamp....