Solar panels in series

[QFour]

Well you learn something everyday. If you connect panels in parallel they have to reach something like 75% of output ie over 14v before they can start charging your battery. If you connect 3 panels in series then each panel only has to generate 5v for them to start charging which is about 25% of its output. The Victrom controller can handle upto 75v so three panels works very well. Panels are rated at 20v

Not agile enough to consider climbing on the roof so 3 x 50w panels will work just fine on the roof of the Carthago and I can access them using a ladder. Biggest area of free roof was right at the front but don't fancy trying to handle a large panels on a ladder and not sure about putting a panel near the front of the roof. Also wanted something light weight so panels weigh 2kg each and are semi flexible from Photonic Universe.

Wiring should be easier and neater as you just daisy chain the panels.

Thought about using 2 x 80w but it is about £50 extra for 10w.

Finally decided how to fix them. Will be using 12mm square anodised aluminum tubes stuck to the roof with Sikaflex. I can use a couple of small pieces of double sided tape to hold them in place and lift them off the roof and then run a bead of Sikaflex down each side of the tube. As there will be a gap the Sikaflex will go under the tube as well. This should result in a good bond to the roof. It will also lift the panel off the roof and give it an air gap underneath. Panels will be held in place to the tubes using pop rivets on the outer edges and double sided tape down the middle.

Must remember the camera this time.

 

[wildebus]

Well you learn something everyday. If you connect panels in parallel they have to reach something like 75% of output ie over 14v before they can start charging your battery. If you connect 3 panels in series then each panel only has to generate 5v for them to start charging which is about 25% of its output. The Victrom controller can handle upto 75v so three panels works very well. Panels are rated at 20v ...

I don't really understand what you are saying here or where you have learnt that? When you say "75% of Output" do you mean 75% of the Panel Voltage as opposed to 75% of the power output? I think that is what you are saying? Have you a link to the info?

For a Victron Controller, for it to turn on, the Input (panel) Voltage needs to be 5V or greater higher than the Battery Voltage, so around ~17V ish on a 12V System. It is true that panels in series will hit the 17V threshold earlier than panels in parallel will, but the amount of extra time multiplied by the amount of harvesting in that time is about the square of virtually sod all.

Below is my System this morning. 3 panels in parallel.

The charger does not switch on until the PV Voltage is 18.12V (Battery bank is at 13.12V).
If I had the 3 panels in Series, the Controller would have switched on around 4AM rather than at 5:15AM. So yes, missed out on 75 minutes of 'active' time, but that 75 minutes would have yielded approximately one half of one AmpHour. The impact at the end of the day can be discounted as any harvesting will have disappeared before the PV Voltage has dropped below the 1V greater than the Battery Voltage threshold

If you had any shading on a panel, the ripple effect of that on the other two panels reducing its output would almost certainly be greater than the benefit of starting the daily solar harvest earlier.

 

[SquirrellCook]

Well you learn something everyday. If you connect panels in parallel they have to reach something like 75% of output ie over 14v before they can start charging your battery. If you connect 3 panels in series then each panel only has to generate 5v for them to start charging which is about 25% of its output. The Victrom controller can handle upto 75v so three panels works very well. Panels are rated at 20v

Not agile enough to consider climbing on the roof so 3 x 50w panels will work just fine on the roof of the Carthago and I can access them using a ladder. Biggest area of free roof was right at the front but don't fancy trying to handle a large panels on a ladder and not sure about putting a panel near the front of the roof. Also wanted something light weight so panels weigh 2kg each and are semi flexible from Photonic Universe.

Wiring should be easier and neater as you just daisy chain the panels.

Thought about using 2 x 80w but it is about £50 extra for 10w.

Finally decided how to fix them. Will be using 12mm square anodised aluminum tubes stuck to the roof with Sikaflex. I can use a couple of small pieces of double sided tape to hold them in place and lift them off the roof and then run a bead of Sikaflex down each side of the tube. As there will be a gap the Sikaflex will go under the tube as well. This should result in a good bond to the roof. It will also lift the panel off the roof and give it an air gap underneath. Panels will be held in place to the tubes using pop rivets on the outer edges and double sided tape down the middle.

Must remember the camera this time.

If you’re using semi flexible panels don’t allow air to get under them. The panels could vibrate when driving and potentially damaging the panels.

We run ours in series to get the benefits from marginal harvesting.

 

[QFour]

I don't really understand what you are saying here or where you have learnt that? When you say "75% of Output" do you mean 75% of the Panel Voltage as opposed to 75% of the power output? I think that is what you are saying? Have you a link to the info?

For a Victron Controller, for it to turn on, the Input (panel) Voltage needs to be 5V or greater higher than the Battery Voltage, so around ~17V ish on a 12V System. It is true that panels in series will hit the 17V threshold earlier than panels in parallel will, but the amount of extra time multiplied by the amount of harvesting in that time is about the square of virtually sod all.

Below is my System this morning. 3 panels in parallel.
View attachment 99040
The charger does not switch on until the PV Voltage is 18.12V (Battery bank is at 13.12V).
If I had the 3 panels in Series, the Controller would have switched on around 4AM rather than at 5:15AM. So yes, missed out on 75 minutes of 'active' time, but that 75 minutes would have yielded approximately one half of one AmpHour. The impact at the end of the day can be discounted as any harvesting will have disappeared before the PV Voltage has dropped below the 1V greater than the Battery Voltage threshold

If you had any shading on a panel, the ripple effect of that on the other two panels reducing its output would almost certainly be greater than the benefit of starting the daily solar harvest earlier.

Hi Wildebus this is the article I was reading .. Here .. Thank you for your input ..

 

[QFour]

If you’re using semi flexible panels don’t allow air to get under them. The panels could vibrate when driving and potentially damaging the panels.

We run ours in series to get the benefits from marginal harvesting.

Hi .. The panels are 4mm thick and have an aluminium backing. They are only 385mm wide with a support in the middle so I think they should be pretty stiff. I can always put a wind deflector on the one that is exposed but two are hidden behind roof lights. I tried sticking one down on a Swift many years ago. I would imagine its still they as it would not come off when it failed. This was 8 years ago and a lot has happened over the years. The panel on the Swift lasted just over a year so was out of guarantee and the company that supplied it didn't really want to know. They suggested I remove it and send it back for them to look at which is why I know how hard it is to get one unstuck.

 

[wildebus]

Hi Wildebus this is the article I was reading .. Here .. Thank you for your input ..

Thanks.
I'll be honest and say I am not a great fan of Nate of Explorist Life. His discussion of what to expect in terms of battery life a few years ago was flawed (and he didn't appreciate me saying so ). But everyone has their own take on things. I didn't agree with that and I don't think his evaluation here is really correct here either.
But he is a popular youtuber who has become a Victron influencer and I don't bother commenting on his stuff. As Churchill said .... 'You will never reach your destination if you stop and throw stones at every dog that barks.'

 

[trevskoda]

No but you will be happy if you stop and pet every cat on your way, I said that not Churchill.