Solar Panel Efficiency?

[PaulRainbow]

Yes, on the flybridge hardtop

2.3 x 1.15

6/7 m and 1.5mm² cable

No obstructions worth mentioning, all done in the marina, nothing significant nearby.


I checked the history tab yesterday after I posted and saw I had 888W highest so that's not terribly out of line with your experience.
Thanks you very much for your input. It made me feel a good bit better about our results.
I'm going to leave things as they are for now, but my son and I were discussing the possibility of raising the panels in the centre [they're side by side fore to aft lenthway] to give a 20/25⁰ aspect and changing the connection to parallel. We may experiment with that on his next visit.

If you change to parallel you double the current, so you have, at max, 100v 50v @ 30a = just over 5v drop !

 

[vas]

but Paul, wont be 100V if in parallel will be 50V.
I'm assuming these panels are 48-50V OC like mine are but maybe wrong.

OP has to check that the cable size he quoted is indeed that thin, could be a typo and we're going off track

 

[Boathook]

My 150W panel has 4mm wire to the Victron MPPT as it is a 6m run one way. I saw 135W from it during the summer. I suspect that if I angled the panel and the batteries needed the power it would have been over 150W.

 

[lustyd]

If you change to parallel you double the current, so you have, at max, 100v @ 30a = just over 5v drop !

I think this is wrong, as was mine. 2x625W panel at 90V and each connected to their own MPPT. That would be 7A per panel. With so many posts it’s hard to see if I missed something but my previous post assumed parallel which seems to be wrong.

Edit to add I think I got 90v from vas so who knows

 

[PaulRainbow]

but Paul, wont be 100V if in parallel will be 50V.

Of course, must still be asleep here

I'm assuming these panels are 48-50V OC like mine are but maybe wrong.

I was assuming the same

OP has to check that the cable size he quoted is indeed that thin, could be a typo and we're going off track

 

[PaulRainbow]

I think this is wrong, as was mine. 2x625W panel at 90V and each connected to their own MPPT. That would be 7A per panel. With so many posts it’s hard to see if I missed something but my previous post assumed parallel which seems to be wrong.

Edit to add I think I got 90v from vas so who knows

He has 2x625w panels, in series to a single controller. At max that would be circa 100v at 15a, with a 7m cable run of 1.5mm cable, you were correct at 2.5v

If he changes to parallel the current will double, so will the voltage drop.

 

[billskip]

Why are you so rude and ignorant ?

It's already been explained how some calculators work.

So I'm rude and ignorant? for asking a simple question?

 

[B27]

15A on 1.5sqmm cable would be well into the area where you should be worrying about cable heating.
Cable would need to be de-rated for the high ambient of being behind a hot panel in a Turkish summer, as well as the two sides being maybe bundled together and in a confined space.

A lot of common PVC cable insulation is not great at temperature.

I'd like to think we're on a tangent here and the cable size is a typo!
1.5sqmm is OK for a 50W 18V panel in Devon.
Not much more IMHO, without 'doing the sums'.

 

[andsarkit]

They won't smoke, not with solar panels, they just loose lots of volts.

That wasn't a serious suggestion but from your figures you could have 40w of heat dissipated in the cables which I would expect to feel warm. I used 2.5mm2 cable on my small 80W panel and felt that they are only just big enough.
What size and length are the cables from the Victron to the batteries? These will be carrying a considerable current at 12V possibly approaching 100A and a small volt drop could restrict the current going into the battery..

 

[Irish Rover]

Just knocked off our work for a short while so haven't been reading this since morning. Cable we used was 2.5mm² not 1.5² as I said - sorry. We decided this morning to change to parallel and have now used 6mm² cable. Just waiting for new MC4 connectors to come to finish the job this afternoon.

 

[vas]

2.5mm2 is thin, 6mm2 is good, I'd stick to series tbh (but I guess it's going to be reasonably easy to try and swap over)
What's the Open Current value of the panels?
What's the distance between MPPT controller and batteries, and what size cable is used there?

 

[PaulRainbow]

2.5mm2 is thin, 6mm2 is good, I'd stick to series tbh (but I guess it's going to be reasonably easy to try and swap over)
What's the Open Current value of the panels?
What's the distance between MPPT controller and batteries, and what size cable is used there?

I'd stick to series too.

 

[Irish Rover]

2.5mm2 is thin, 6mm2 is good, I'd stick to series tbh (but I guess it's going to be reasonably easy to try and swap over)
What's the Open Current value of the panels?
What's the distance between MPPT controller and batteries, and what size cable is used there?

Open current 50.35v. 35mm² controller to bus bar, max 1.5M distance. Busbar to batteries around 60cm distance, with original cable around 60mm², I think.

 

[rogerthebodger]

Open current 50.35v. 35mm² controller to bus bar, max 1.5M distance. Busbar to batteries around 60cm distance, with original cable around 60mm², I think.

Sorry hi data makes no sense.

50,35 v i a voltage not a current

60mm² is like a cable area and 60mm² is a very big cable for a boat

 

[PaulRainbow]

Sorry hi data makes no sense.

50,35 v i a voltage not a current

60mm² is like a cable area and 60mm² is a very big cable for a boat

The 60mm cable is the original cable from the batteries to the main positive busbar. It's not big for a motorboat, especially at 12v.

I'm currently changing the batteries on a 40ft sailboat that has 4x140ah batteries and is wired with 60mm cables

My next job is re-wiring the DC systems on a 42ft sailboat, fitted with 5 110ah batteries, with 70mm cables.

Lots of boats these days with big power requirements, even if it's for short periods. I can draw 200a @ 24v from my batteries, that needs substantial cabling.

 

[Irish Rover]

The 60mm cable is the original cable from the batteries to the main positive busbar. It's not big for a motorboat, especially at 12v.

It was a guess. Truthfully I have no idea. Could be 60 or 65 or 70.

 

[Irish Rover]

This stuff a bit above my pay grade so make of it as you will.

 

[vas]

Sorry hi data makes no sense.

50,35 v i a voltage not a current

60mm² is like a cable area and 60mm² is a very big cable for a boat

my mistake!
Open circuit voltage is the right term
I've got 70mm2 cables from lifepo4 bank to bus bar @24V, dont even get warm when 2kW watermaker works through the victron multiplus

 

[Irish Rover]

We got the panels back working just before 15.30 this afternoon. They were producing 490/495W There was far less fluctuation in the watts and voltage than yesterday. I switched on the water heater through the inverter and the battery voltage dropped from 12.9 to around 12V very quickly but held around there for the 30 minutes or so it took the water heater thermostat to turn it off. Battery voltage immediately recovered to around 12.7 and was building from there. Panels were still producing around 185W when we left the boat at 17.40. We're heading off for a few days tomorrow and will be spending the nights at anchor so I'm curious to see how the panels will perform.

 

[vas]

just note what the victron app reports at between 1pm -2pm that's the peak right now.