Solar upgrade: working out my limitations (1 Viewer)

[Ridgeway]

So before i go out and buy over specced panels i thought it wise (for once) to check my limitations based on existing installation:

So current set up is:

4mm cables (yep i know…)
Victron 100 / 50 MPPT
10m cable run (max, it could be 8m but i rounded it up)
2 x 110w panels (wired in parallel)

I’d rather avoid changing the cables and i see that as my limitation so i wonder what is the safe maximum i could add to that set up ? Pretty sure the Victron MPPT has plenty of capacity but again need to be careful there as well.

I did get a price from my dealer but i though he misunderstood my request for a spare kidney

 

[funflair]

You could add two more the same and run them in series to the existing ones I guess, Victron 100/50 should be OK with that.

 

[RogerIvy]

As funflair said, add in series.
Panels in series increase voltage but not amperage, so the thinner cable can generally handle it.

Note however:
When you combine panels of different capacities in series each panel in the array effectively operates at the amperage of the “weakest” panel.
When you combine panels of different capacities in parallel each panel in the array effectively operates at the voltage of the “weakest” panel.
If you do the math you can figure out how much you’ll really gain with the new panel.
If you add panels that are identical then it’s easy.
Sometimes it’s better to remove existing panels and replace with new array of identical panels.
Note however that sometimes a combination of parallel and series is your best option.
It‘s all about the math

 

[Ridgeway]

Hadn’t thought of swapping out the old panels, that seems like a great idea actually. I may in that case go for 4 x 150w new panels and swap out those 2 original 120w which are anyway the dreaded direct mount type so not sure how efficient they are or how reliable they will be long term…

Food for thought

 

[Raul]

So before i go out and buy over specced panels i thought it wise (for once) to check my limitations based on existing installation:

So current set up is:

4mm cables (yep i know…)
Victron 100 / 50 MPPT
10m cable run (max, it could be 8m but i rounded it up)
2 x 110w panels (wired in parallel)

I’d rather avoid changing the cables and i see that as my limitation so i wonder what is the safe maximum i could add to that set up ? Pretty sure the Victron MPPT has plenty of capacity but again need to be careful there as well.

I did get a price from my dealer but i though he misunderstood my request for a spare kidney

From the roof, do you have two pairs of 4mm2 from each panel to controller? Or a single pair.
If a single pair, i would sell the two panels and go for new larger panels in series. Your controller can handle 700w at 12v, but its a matter for the existing cable to keep the amps down and up the voltage so you minimise losses. Hence, new panels with high voltage.

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[Raul]

Hadn’t thought of swapping out the old panels, that seems like a great idea actually. I may in that case go for 4 x 150w new panels and swap out those 2 original 120w which are anyway the dreaded direct mount type so not sure how efficient they are or how reliable they will be long term…

Food for thought

There are still few about Panasonic 250w that run at low 5 amps but 45-50v. That would be my top choice. You could even run them in parallel, the 4mm2 will carry the 10amp fine.

 

[Speve]

I added two panels to my system and used a new mppt for them leaving the existing alone as they worked really well I’ve used my total solar to 400w now and that keeps my batteries fully charged

 

[Ridgeway]

From the roof, do you have two pairs of 4mm2 from each panel to controller? Or a single pair.
If a single pair, i would sell the two panels and go for new larger panels in series. Your controller can handle 700w at 12v, but its a matter for the existing cable to keep the amps down and up the voltage so you minimise losses. Hence, new panels with high voltage.

Single pair unfortunately knowing that what’s my max watts i could go for ? And this assumes 2 new panels (Could also be 4 smaller panels)

 

[Raul]

Single pair unfortunately knowing that what’s my max watts i could go for ? And this assumes 2 new panels (Could also be 4 smaller panels)

Avoid four smaller panels if you can, and you will avoid high amps. Two biger panels will be better as will run at higher voltage. The max 700W from panels to controller is best to be kept at high voltage and low amps as i mentioned previous. You only have a pair of 4mm2, and 8m will not help you if you push 4 panels (16A) at 36v.
Increase the voltage and reduce the amps by choosing two larger, rather than 4 smaller panels.
Of course all depends on your roof space.

 

[RogerIvy]

Single pair unfortunately knowing that what’s my max watts i could go for ? And this assumes 2 new panels (Could also be 4 smaller panels)

It’s not the watts you need to think about for the cable, it’s the amps. Different makes have potentially different voltages and therefore different amps.

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