4x310W Panels Series/Parallel

[AJM]

Hi Guys

I have the above mentioned solar panels on a victron 100/50 blue solar mppt. The Max PV Yield I get is +-1000W would this be considered normal.

I would suspect a bit more my pv cable is 4mm and 10m long.

Regards

[Guest]

Depends.

Panels connect in series or 2 series and 2 parallel?

Few things to keep in mind:
Panels only produces what is needed. Do you exceed the 1000w they produce currently?
Are the panels flat mounted or is there a lot of ventilation for as you know temp of panels has a rather big effect.
Orientation?
Cable losses - have you checked the voltage losses over that distance, and the actual voltages measured?

 

EDIT: Out of my 930w panels, after some TLC, for I never got more than +-890w under load, I now have seen 1089w easily on certain days.

EDIT 2: And I KNOW if I replace the 6mm2 wire with 10mm2, I would get more. for I am reaching 15m+
 

[AJM]

This is how my panels are connected.

2 panels are connected +/- other 2panels are connected +/- then I use Y connectors to join the two sets together if this makes sense.

Panels have good ventilation and are not on a flat roof they are facing north.

[Guest]

So they are series / parallel. 

Your voltage at max power is therefor +-72.6 @ 17.2amps which ideally should see 1248.72watts.

If you connected them in series, you could get better volts and less losses at +-145.2v.

BUT if it is a perfect cool sunny day, you could be facing 181.4v which is quite a bit over the 150v max.

Three of them on the other hand in series would be better at 108v or best ever and safe at 136v perfect day maximum.

Get another 2 and you have 3 in series and 2 in parallel IF you can use all the power.

Why? The higher the volts the less losses you have the better it all works.

 

[___]

If you get around 80% of spec you're doing about the same as me. I rarely see full capacity, and it seems to be related to temperature, for the days that I do see nice yields close to the rating are usually cool semi-cloudy days. Since 310*4*0.8 ~= 1kwp, it sounds about right.

The cabling might play a part too. Imax on those panels are probably 7A-8A, with two in parallel on a 4mm cable, perfectly within spec, but getting up there. Usually that kind of cable has a resistance of 5Ω per kilometer, and if you have 10 meters of it (times two I assume, for positive and negative), then 0.02 * 5 = 1Ω, times 16 amps, that's 16 volts drop, times the current is 16W lost. That's 1.5% and probably nothing to worry about. Cables should be good for 25A, I've pushed them to 35A and though they get warm to the touch they survive... :-)

[___]

1 hour ago, The Terrible Triplett said:

BUT if it is a perfect cool sunny day, you could be facing 181.4v which is quite a bit over the 150v max.

It's a 100/50. Can't go up to 150, the arrangement is optimal already :-)

[Guest]

1 hour ago, plonkster said:

It's a 100/50.

O my word!!! My Apologies @andriesmalan I even Google it for the specs. (facepalm)

Feel like and idiot for not double checking the post.

[AJM]

Thanks for all the replies would I benefit if I change the pv cable to 6mm or 8mm. Or would that just be a waste. 

[AJM]

Some info from the mppt in the attachments below. 

 

[Chris Hobson]

As Plonky said within spec 4mm² will result in 2% losses really not necessary to go thicker. I too get about 80% of maximum unless we have unusual circumstances.