Wanting to add more solar on existing charge controller but different panels

[uk-solar-guy]

Now let me preface please do not just tell me to get another SCC. I am well aware there will be a performance hit for doing this but I want to do it anyway as it still give a large net gain and solar panels are cheap while a charge controller isn't and is just easier to add to existing SCC which has plenty more headroom. On the reckoning below it would be only a 12% hit.

 

As this is a UK based forum I hopefully don't need to persuade as to the benefits of getting more solar, commonly referred to as overpanelling, for cloudy weather.

 

I know that it is generally told as verboten to add parallel strings of different number on the same SCC but I also read a couple of posts here and there of users doing it successfully just that it was 'advanced' so discouraged in general.

 

Through more research I have been informed that it is fine to do this so long as you aim to keep the Vmp and Imp the same.

 

My charge controller has 150Voc with 138V for 25c.

 

Here is the proposed setup:

 

Existing 100W panels, currently in series:

Vmp: 19.4
Imp: 5.2A
= 58.1V x3 in series.

Planned new panels:

430W rated each:

Vmp: 32.9
Imp: 13.07
= 65.8 x2 in series.

 

So that makes 3 series for 1 string, 2 series for another then both of them paralleled.

 

The 430W panels, being the higher voltage figure would take the efficiency hit. The optimal output would be 860W. With the voltage drop would get 759. So 12% performance hit. 300 + 759 = 1059W (compared to 1160W full power).

Do those calculations look correct and ok plus any other considerations to take into account? Would the additive current mean I had to change anything else in terms of wiring or fusing for the 300W string?

 

As there is no more room up top I would plan to ground mount the 2x new ones. I actually reside in my van currently but am parked stationary in the same place week to week on a private piece of land. I plan to make the new panels quick connect/disconnect so I can do so easily when I want to drive off and back again. I am looking at using anderson connectors for this and I already have a Kraus and Naimer 2 pole isolator for the existing solar which I would use to switch off the solar when connecting/disconnecting.

 

When the ground mounted panels were disconnected I was given the suggestion to get a masterseal socket, and remove the provided sockets, in order to stow away the connected shielded from the elements when not in use as there is no weatherproof storage on the field.

[JohnMo]

Why are you faffing about with a 300W string? Just bin it and buy new panels - 500W panel is only £67.

 

Your issue adding to the other panels, is the big panels may only output the same as the old string unless on a separate mttp. Plus to keep everything happy you will likely need to add optimisers, which cost the same as the new panels.

 

 

[Beelbeebub]

What's the max output of your controller? 

 

It looks like you have 3x 100w panels. 

 

That's less than the output of a single modern standard panel. panel, just buy one extra and bingiveaway/reuse the old ones. 

 

https://www.cityplumbing.co.uk/p/dmegc-450w-all-black-solar-panel-2mm/p/120106

 

£61 each for 450w.

 

Under £200 to quadruple your capacity

 

[uk-solar-guy]

55 minutes ago, Beelbeebub said:

What's the max output of your controller? 

 

It looks like you have 3x 100w panels. 

 

That's less than the output of a single modern standard panel. panel, just buy one extra and bingiveaway/reuse the old ones. 

 

https://www.cityplumbing.co.uk/p/dmegc-450w-all-black-solar-panel-2mm/p/120106

 

£61 each for 450w.

 

Under £200 to quadruple your capacity

 

 

Yes I get that but the 300 are on my van so efficiency and cost are not the only factors when I made the van build.

 

I got flexibles as I wanted it to be 'stealth' at the time and it looks like a bog standard panel van from the outside with these low profile flexibles which is a large plus. Now if I were making the build again today I would not be bothered about the stealth factor but it does have its benefits so don't wish to take these off.

 

Also no matter the cheapness I would be limited by space anyway so probably won't get a large panel up there. I just looked and that would not fit on the van for even one so a moot point anyhow. There is an air vent in the middle of the roof anyway.

 

Most of the year they are perfectly fine for my solar requirements it is just the shorter days and worse whether that I need a boost. Ye I know I can buy a generator but I chose this idea instead as it is still clean energy.

 

When parked up on the field the above are not an issue and can go with large and efficient but I otherwise am happy with my compact setup when on the road with my van. I hate the obvious telltale vanlifer look that nearly all other converted vans have.

 

Also the added bigger panels do not need to be optimal either, just push me over the bump enough to give me more than I use daily.

 

Oh those are some nice priced panels you linked though. What I had noticed with most places was even if the price looked good you would then be looking at 100-150 for shipping but I see they even offer free shipping over 75. The ones I listed in OP were offering free shipping within the catchment area, which I happened to be in.

Edited Monday at 09:20 by uk-solar-guy

[JohnMo]

Buying Panels - City Plumbing are in most areas and super cheap for panels. You have a van so could you collect? But most electrical wholesaler sell panels now. So are the additional panels just going to be free standing when parked up?

 Need the full story really

[uk-solar-guy]

17 minutes ago, JohnMo said:

Buying Panels - City Plumbing are in most areas and super cheap for panels. You have a van so could you collect? But most electrical wholesaler sell panels now.

 

Hmm I have never heard of them before and thought it a strange for a plumbing company to be selling solar panels. Doesn't sound like good branding to me.

 

The van is small and also packed with living stuff so very little room for large items. Doesn't matter anyway as the site states free delivery over 75.

 

17 minutes ago, JohnMo said:

 

So are the additional panels just going to be free standing when parked up?

 Need the full story really

 

I wrote the full story in my OP.

 

3 hours ago, uk-solar-guy said:

As there is no more room up top I would plan to ground mount the 2x new ones.

 

I want to ground mount them and have a quick connect/disconnect for when I drive off and back.

Edited Monday at 10:48 by uk-solar-guy

[JohnMo]

3 minutes ago, uk-solar-guy said:

quick connect/disconnect for when I drive off and back

Would be careful doing that, you normally switch source off last, otherwise you be getting big sparks occurring on disconnecting or damaging the charge controller, or yourself.

[uk-solar-guy]

1 minute ago, JohnMo said:

Would be careful doing that, you normally switch source off last, otherwise you be getting big sparks occurring on disconnecting or damaging the charge controller, or yourself.

Have you read the OP? I have written all this...I put that I will have a solar isolator to switch them off before doing that.

[uk-solar-guy]

4 minutes ago, JohnMo said:

Would be careful doing that, you normally switch source off last, otherwise you be getting big sparks occurring on disconnecting or damaging the charge controller, or yourself.

 

3 hours ago, uk-solar-guy said:

I already have a Kraus and Naimer 2 pole isolator for the existing solar which I would use to switch off the solar when connecting/disconnecting.

[Nickfromwales]

2 minutes ago, uk-solar-guy said:

 

That sounds great on paper, not so great when you go and do so in any kind of daylight.

 

You need to cover the panels to go full blackout if not doing this when dark. Needs to be sequenced to protect all equipment, and you!

[Nickfromwales]

City Plumbing are one of the biggest merchants in the UK, and I’ve had an account with them for nearly 3 decades. 

[uk-solar-guy]

3 minutes ago, Nickfromwales said:

That sounds great on paper, not so great when you go and do so in any kind of daylight.

 

You need to cover the panels to go full blackout if not doing this when dark. Needs to be sequenced to protect all equipment, and you!

 

What are you quoting? It is empty. What is the issue if there is a solar isolator? That is what they are for no? I have used the isolator I have already to isolate the solar circuit of my existing panels, so what is different?

[Nickfromwales]

9 minutes ago, uk-solar-guy said:

 

What are you quoting? It is empty. What is the issue if there is a solar isolator? That is what they are for no? I have used the isolator I have already to isolate the solar circuit of my existing panels, so what is different?

Knowledge. Experience. Information. The things you will find here to be plentiful.

 

Is it better to know a risk and be informed, or come back here asking how to fix it after it broke through misadventure?

 

Buildhub is a place where people discuss things, providing reason and rationale; some other forums are more like boxing rings which is great for exchanging blows.

 

I am simply stating something because what you said raised a red flag, eg ‘simply’ disconnecting the DC side to go scoot off to the shops.
 

There are strict guidelines for decommissioning a PV system, regardless of size or location, so as to avoid damage to equipment or personal injury.

 

No matter what DC isolator you say you’re buying, the rules are the same eg never disconnect panel strings in sunlight or under any load, and they need to be the last thing shut down.

[uk-solar-guy]

3 minutes ago, Nickfromwales said:

Knowledge. Experience. Information. The things you will find here to be plentiful.

 

Is it better to know a risk and be informed, or come back here asking how to fix it after it broke through misadventure?

 

Buildhub is a place where people discuss things, providing reason and rationale; some other forums are more like boxing rings which is great for exchanging blows.

 

I am simply stating something because what you said raised a red flag, eg ‘simply’ disconnecting the DC side to go scoot off to the shops.
 

There are strict guidelines for decommissioning a PV system, regardless of size or location, so as to avoid damage to equipment or personal injury.

 

No matter what DC isolator you say you’re buying, the rules are the same eg never disconnect panel strings in sunlight or under any load, and they need to be the last thing shut down.

 

I was not being snarky I was stating that your above post the quote is empty. So I was asking what you were quoting so I could know what you were responding to:

 

[Nickfromwales]

 

Sorry. Just realised it didn’t show the re-quotes.

 

Wrong button! 

[Beelbeebub]

32 minutes ago, uk-solar-guy said:

 

Hmm I have never heard of them before and thought it a strange for a plumbing company to be selling solar panels. Doesn't sound like good branding to me.

 

The van is small and also packed with living stuff so very little room for large items. Doesn't matter anyway as the site states free delivery over 75.

 

 

I wrote the full story in my OP.

 

 

I want to ground mount them and have a quick connect/disconnect for when I drive off and back.

Ah I get it. 

 

Might in suggest, rather than trying to parallel them up, with the attendant issues, you arrange it such that when you are at "home" you totally disconnect from you van mounted panels and just use as many standard panels as you want, then switch over to the flexible for mobile use. 

 

You can make up for the loss of the flexible panels by adding a single extra standard panel to your ground array. 

 

Much less chance of issues. As mentioned the disconnection and reconnection needs to be handled with some care. 

[uk-solar-guy]

6 minutes ago, Nickfromwales said:

 

Buildhub is a place where people discuss things, providing reason and rationale; some other forums are more like boxing rings which is great for exchanging blows.

 

 

 

Also I agree I really dislike the adversarial nature of a lot of electronics forums. I have not been researching the field for long, relatively, the last few years, but was quite shocked at how confrontational many are in it. Seems electronics and lackluster social skills and classic male member measuring go hand in hand.

 

I was reading a thread yesterday where an innocent question from OP ended up in a pissing match between 2 respondents about who knew more about electronics than the other and each one reeling off their purported expertise to try and trump the other. A pathetic display to any indifferent onlooker.

[uk-solar-guy]

10 minutes ago, Beelbeebub said:

Ah I get it. 

 

Might in suggest, rather than trying to parallel them up, with the attendant issues, you arrange it such that when you are at "home" you totally disconnect from you van mounted panels and just use as many standard panels as you want, then switch over to the flexible for mobile use. 

 

You can make up for the loss of the flexible panels by adding a single extra standard panel to your ground array. 

 

Much less chance of issues. As mentioned the disconnection and reconnection needs to be handled with some care. 

 

 

Maybe but all my electrics - cooker, lights, and so on - are in the van so whatever other source will have to be disconnected and reconnected somehow? so same issue no? albeit avoiding the related compatibility issues of mixing panels?

Edited Monday at 11:29 by uk-solar-guy

[-rick-]

I assume you have a battery to run off during the night. Disconnecting the solar panels from the charge controller shouldnt interfere with your consumers.

 

I know you said you didn't want to think about a second charge controller but I wonder why? It seems like an easy option and not expensive. Are you using an ecoflex or similar?

[JohnMo]

The normal switch off sequence. Downstream of inverter or charge controller, you switch of the load path via  a dedicated isolator switch. Then once isolated you switch off the PV panels via a second isolator switch. The isolation switches are suitably rated DC switches for the PV and again suitable rated for the inverter or charge controller (depending on if AC or DC). This way nothing goes bang including yourself. Reconnection is the opposite, you start at the PV and work towards the load.

 

I really would just separate existing and new, way less complex, way more safe. 

[-rick-]

31 minutes ago, -rick- said:

I know you said you didn't want to think about a second charge controller but I wonder why? It seems like an easy option and not expensive. Are you using an ecoflex or similar?

 

I apologise I just re-read your original post. A victron charge controller for 15A 100V (so 2 strings of two panels) is about £70 so not much difference than the cost of a panel and does buy you some redunancy (which is useful if you go on trips to the middle of nowhere).

 

At 70V on a system isolated from ground safety concerns are less than a traditional system but you do stlil need to pay close attention to them.

 

 

[Beelbeebub]

4 hours ago, uk-solar-guy said:

 

 

Maybe but all my electrics - cooker, lights, and so on - are in the van so whatever other source will have to be disconnected and reconnected somehow? so same issue no? albeit avoiding the related compatibility issues of mixing panels?

I assume your flexi panels, charge controller and some small leisure batteries are on the van?

 

You arrive at "home", park up. 

 

Go through your disconnect routine to unplug/isolate your flexi panels from your charge controller. 

 

You now have a van with no solar panels (as far as it's aware) running as though it is night time. i.e. off batteries. 

 

Unlock your little waterproof box, unspool the cables from your fixed panels - however many your controller will handle and spsce/money allows and go through your reconnection routine. 

 

Now your charge controller is hooked up to some panels, it doesn't care they are different from the van mounted ones, it just goes about it's business. 

 

Basically all the work you were going to do, except you just need to disconnect your flexi panels rather than have them in parallel.

 

[uk-solar-guy]

4 hours ago, JohnMo said:

The normal switch off sequence. Downstream of inverter or charge controller, you switch of the load path via  a dedicated isolator switch. Then once isolated you switch off the PV panels via a second isolator switch. The isolation switches are suitably rated DC switches for the PV and again suitable rated for the inverter or charge controller (depending on if AC or DC). This way nothing goes bang including yourself. Reconnection is the opposite, you start at the PV and work towards the load.

 

I really would just separate existing and new, way less complex, way more safe. 

 

Well I already have both of those isolators in place so just a case of going through the sequence.

 

I don't see how separating old from new will be safer as the process for disconnecting and reconnecting will be the same won't it so the safety is the same? By mixing the panels it is only a question of whether they will work to an appreciable degree or not isn't it? I could just buy the panels and try them all through the same SCC and then if it didn't work well then I can always get the second SCC or do the separation. I am not aware that it will damage the panels by trying to route them all together since I am staying within the limits of the controller?

 

3 hours ago, -rick- said:

 

I apologise I just re-read your original post. A victron charge controller for 15A 100V (so 2 strings of two panels) is about £70 so not much difference than the cost of a panel and does buy you some redunancy (which is useful if you go on trips to the middle of nowhere).

 

Hmm well I just felt like getting more out of this controller if it has the headroom for it. As above I can try all on one and look at my options after if it didn't work well.

 

3 hours ago, -rick- said:

At 70V on a system isolated from ground safety concerns are less than a traditional system but you do stlil need to pay close attention to them.

 

 

 

A system isolated from ground can you explain what it means, as opposed to what? I am not too up on the nomenclature of grounding and certainly not for house electronics, though I have done my grounds as recommended.

 

20 minutes ago, Beelbeebub said:

I assume your flexi panels, charge controller and some small leisure batteries are on the van?

 

You arrive at "home", park up. 

 

Go through your disconnect routine to unplug/isolate your flexi panels from your charge controller. 

 

You now have a van with no solar panels (as far as it's aware) running as though it is night time. i.e. off batteries. 

 

Unlock your little waterproof box, unspool the cables from your fixed panels - however many your controller will handle and spsce/money allows and go through your reconnection routine. 

 

Now your charge controller is hooked up to some panels, it doesn't care they are different from the van mounted ones, it just goes about it's business. 

 

Basically all the work you were going to do, except you just need to disconnect your flexi panels rather than have them in parallel.

 

Yes, it is another option. As above I am thinking why not try rigging them all together first and then try other options if it doesn't work.

 

One wants the max Wattage you can squeeze in that period so don't want to leave money on the table so to speak. Of course it is possible they perform so poorly that it would work better to have the ones on top disconnected but don't know til I try.

 

In regards to the 300W, if I did try is the maximum fuse rating? Someone mentioned this could be a possible concern, elsewhere but did not explain. The max fuse rating for each 100W panel is 15A so is that a problem or not?

Edited Monday at 15:52 by uk-solar-guy

[JohnMo]

12 minutes ago, uk-solar-guy said:

One wants the max Wattage you can squeeze in that period so don't want to leave money on the table so to speak. Of course it is possible they perform so poorly that it would work better to have the ones on top disconnected but don't know til I try.

 

In regards to the 300W, if I did try is the maximum fuse rating? Someone mentioned this could be a possible concern, elsewhere but did not explain. The max fuse rating for each 100W panel is 15A so is that a problem or not?

A quick Google search and the following pops up first hit

 

Searched for "running mismatched pv panel parallel strings"

 

Running mismatched PV panel parallel strings is generally a bad idea because it reduces overall system power output and can cause damage due to current imbalances. The string with the lowest voltage will limit the total voltage, while the string with the lowest current will essentially become a load on the other strings. This can lead to reverse currents, overheating, potential damage to the lower-performing panels, and reduced efficiency for the entire array. For optimal performance, it's best to keep strings with identical panel characteristics connected in parallel.

[-rick-]

54 minutes ago, uk-solar-guy said:

A system isolated from ground can you explain what it means, as opposed to what? I am not too up on the nomenclature of grounding and certainly not for house electronics, though I have done my grounds as recommended.

 

Sorry I slightly misspoke. I meant earth. If you are in a vehicle your electrical system will not be connected to earth. You will ground your system to the negative battery terminal (and likely chassis of vehicle) but the tires will isolate your system from earth. There are some different rules for systems like this to normal domestic systems. I'm not an electrician and thats about as far as my memory goes (from looking at this out of curiosity a while ago).

 

My comment was made more from the perspective as I saw what the others had said in this thread seemed to be coming from the perspective of a domestic system and wanted to cover the possibility that you read them as such and thought you could ignore them because your situation is different. Having read your reply it seems like you have all the bits you need for protection so my point is somewhat moot.