Thinking of switching Solar Panels from Parallel to Series - should I or shouldn’t I?

[Carpmart]

I’ve two questions please!

1. So I’ve got three matched Craig Solar 200w panels flat mounted on the roof. These are currently connected in parallel as I was concerned about a series approach delivering lower yield with shading.

They are connected to a Victron MPPT 50/100. I’ve only got a 6mm2 cable from roof to MPPT but I have got a 10mm2 cable ready to install to reduce cable loss. It’s a 2.5m cable run from cable junction to MPPT.

All is working fine at the moment, but could it be even better if I series string these panels?

I am particularly interested in earlier and later solar yield as with higher voltage series provides, the differential between a 13v+ lithium battery bank will be much higher and the MPPT will be ‘doing its thing’ for longer.

Anyway, I’d appreciate your thoughts please?

2. To get enough solar in the winter, I’ve now got two off 2x80w tilting panels, so it’s effectively 4x80w sunshine solar panels. The winter just gone I was using just one pair (effectively 160w) which I can angle in Nov/Dec/Jan/Feb low winter sun. I’ve recently acquired a second, taking me up to 320w. I’m going to run these (four panels) in series (or maybe 2S 2P is this better?) as I use a long 4mm2 to enable me to move them around easily during the day.

I’ve a separate MPPT 100/20 but will 20A be enough for 320w of solar?

Thanks in advance

 

[Lenny HB]

Last question first the 100/20 is rated for 290 watts of solar on a 12v system. If you go over the max with Victron they keep working but lose the excess in heat. It won't be very often you will be getting the max from the panels.

I would stick with parallel, the small gain you would get in series is more than offset by the shading problems you could get.
The existing 6mm sq cable will be fine, output from panels will be about 17.5v when charging so a volt drop of 3% at max current.
When you have plenty of sun 3% won't worry you and in winter with the panels only outputting 20% - 30% of their max the volt drop will be insignificant.

 

[Steve and Denise]

I have our 3 Victron 175w in series through a 100/30 often hit 30 amps but has never got hot and delivers similar figures throughout the day when compared with a 2xs 2xp system and have monitored this quite regularly.
I know I am a bit over panelled and may get around to changing up to a 100/50

 

[cyberyacht]

Not such a big array but I have 3x100w in series. At least it gets the voltage up to a sensible level when the light is low.