SCC 100/50 low W-V

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link-cat asked Jun 16, '22

SCC 100/50 low W-V

Hello, I will try to be precise. I have contacted my distributor of victron devices, and he has stopped selling, so I wonder if you could give me an indication here.

My system. Camper van, lifepo4 280ah 12v battery. 5 100W solar panels in parallel, mppt 100/50, orion 12/12, smartshunt, multiplus 12/1600/70 and CerboGx.

I would like to have the panels in series, but they can reach 116v and my charger is the 100/50. I can't fit another 100W plate to do series-parallel.

Since 9 days ago, my batteries have been discharging down to 20% (then I get the vrm warning). During the day the solar generates about 40-60W on average, before (even last summer, I had about 150-160wh).

Since a few days ago, the plates do not generate more than 40-60W, at some point of the day they can reach 150W (but only for a moment), then sometimes it goes down to 0W (lots of sun and no clouds).

I have checked all the connections and everything seems to be in order. I just need to check the mc4 connections of the solar panels, but it is quite inaccessible for maintenance and I would like to discard everything else first.

The battery is below 80% (I have done the tests with the SOC from 20% to 90%, same results.)

I have tried charging the battery from the alternator (Orion) it takes 18amps, and from the multiplus (takes 65amps) no problem. The battery is fine, and the cells are balanced.

A few days ago (as always, fine)

Now:

Just to add it, half of the time, the SCC is not giving any W as can be seen here (it never did it something like this, at least with the battery not full).

Thank you for your time, I hope I can fix it..

MPPT Controllers solar

victron1.png (25.8 KiB)

victron2.png (20.6 KiB)

victron3.jpg (60.1 KiB)

victron4.jpg (52.4 KiB)

1655388739171.png (63.4 KiB)

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Alexandra ♦ commented · Jun 16, 2022 at 12:21 PM

@link_cat

The 100V input is a hard limit. So the proposed 116V is not acceptable.

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link-cat Alexandra ♦ commented · Jun 16, 2022 at 12:28 PM

Yeah, because of that the panels are wired in parallel (VOC 21,6v, VMPP 17,9, Impp5,72 and ISC 6,24). Here are the details I used to size the SCC and panels.

vic

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1655382613802.png (52.5 KiB)

Alexandra ♦ link-cat commented · Jun 17, 2022 at 11:43 AM

@link_cat

You would probably do better with 3 in series rather than 5 in parallel. Higher voltage. Wastes the other two panels though so I guess not entirely what you would want.

Or 2 s and 2p.

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link-cat answered · Jul 03, 2022 at 11:11 AM

Finally, with two friends and a good barbecue, we were able to dismantle the solar panels. The connections were all tight and good, all the panels were giving about 18-19 volts in open circuit.

Finally, once the calculations were done through the victron website, we mounted 4 panels in series (93,5v open circuit max at minimum temperature) and left one panel disconnected (future purchase of a cheap regulator and that panel will go to the vehicle's starter battery).

The 4 solar panels add up to about 80v (open circuit) and at full power output about 250-320w. Now everything is working normally.

I can't understand what went wrong, the parallel system worked fine for over a year, now I have "lost" one solar panel, but the battery is back to 100% at 11am.

Thanks to all of you for your advice, and I hope this can be useful to someone in a similar situation.

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Answer 1 · 2022-06-16T14:08:26Z

kevgermany answered · Jun 16, 2022 at 02:08 PM

What are the battery settings in the mppt?

What happens if you test by wiring 2 or 3 panels in series, leaving the others disconnected? Cover the panels before remaking the connections.

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link-cat commented · Jun 16, 2022 at 02:21 PM

Starting with lifepo4 default parameters, changing a bit the absorption and float voltage. But the SCC is always in "bulk" but now sometimes gets 0 current.

Unfortunately, I can't rewire in series (2-3 panels) (bc I need some help to take it off from the roof, and I'm alone and not than physically able to do that on my own) Because of that I was trying to figure it out what could be the problem, a seller I just called (not from who I bought it) told me that it could be a faulty charge controller unit.

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victron6.jpg (58.4 KiB)

Answer 2 · 2022-06-16T15:04:21Z

seb71 answered · Jun 16, 2022 at 03:04 PM

In your second screenshot (from the first post) the PV voltage is only 15.18V. Is that typical?

How are the PV panel parallel connections made? Combiner box or using those "Y" MC4 adapters?

If connecting 2-3 panels in series is difficult, can you test each panel alone?

13.8V Absorption voltage for LiFePO4 is on the low side, but I don't think that's the cause.

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link-cat commented · Jun 16, 2022 at 03:39 PM

I lost all the data I had when I reinstalled venus OS because I wanted to discard any firmware error, so I lost the data. If I shut down the SCC, the PV voltage climbs up to 19v (more or less), when the SCC is on and working on bulk, used to slow the PV voltage to 14,9v (with 100W of solar going from the solar to the battery).

The parallel connections were made using Y adapters (as can be shown in the following picture). It has been working great for a year. I figure it out isn't the Y connectors, but could be.

It is the same problem, I will need to travel a bit to find someone to help me get up on the roof to check each panel, and also to test it wired in series (2-3-4). I think is the only way to achieve it.

Here's a photo of the roof:

On the other hand, when I disconnect the SCC (switch between the panels to the SCC) and re-connect it again, the SCC is able to charge to 90-150 depending on the day, because of that I was thinking that has to be something wrong on the charge controller. But I'm not an expert.

Just tried to disconnect and reconnect the switch (panels to SCC) and the PV voltage and W did this (PV voltage goes up, mppt doing his job +-100W, and then kabum, few minutes to 30-40W and with the exact amount of PV voltage, zero Watts, and it's doing this all day, between 40-50W => 0W => 40-50W...∞).

Also to be noticed, that I have a 10 amp fuse on each positive from each panel, just to explain everything, it could be that some of them has blown..but again, hard to get up to check it.

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1655393092947.png (258.7 KiB)

seb71 link-cat commented · Jun 17, 2022 at 06:28 AM

The PV voltage is borderline (but you say the system worked as expected in the past).

Wiring 2 or 3 panels in series would give an answer to that question. Probably 4 in series is also OK, but do not wire 4 panels in series unless you are certain that the string voltage remains under 100V at all times (even in cold weather). Most likely you can't wire all 5 in series with that 100/xx charger.

Unless you can test with another charger (or try your charger with another PV) I can't see anything to test which does not involve dealing with the PV wires.

-------

The wires from the Y adapters are 4mm2 or 2,5 mm2?

In your drawing they are marked as 4 - 2,5 mm.

What's the PV panel Isc?

2,5mm2 would be too small cross section. 4mm2 might be acceptable.

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Answer 3 · 2022-06-17T03:44:37Z

kevgermany answered · Jun 17, 2022 at 03:44 AM

It's possible that it's the controller, but could be other things. You're going to have to get help with the diagnosis.

Check the wiring and connections carefully. With the panels wired like that it's pretty straightforward to disconnect a panel at a time and check the effect. Also worth finding the maker's recommendation for your batteries and tweaking the charge controller to match. But as @Seb71 said, doesn't look like that.

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Answer 4 · 2022-06-19T10:00:32Z

link-cat answered · Jun 19, 2022 at 10:00 AM

Thank you all very much for your help, I plan to go see a friend next week to see if we can disassemble the solar to check it the wires and voltages. In case the wiring is OK, and the solar panels are OK, then it would be a problem with the charger. I will keep you informed.

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Answer 5 · 2022-06-26T17:18:33Z

link-cat answered · Jun 26, 2022 at 05:18 PM

Today finally a friend of mine has been able to help me with the diagnosis, we will try this week to uninstall the solar panels. However, let's see if with what we have achieved you can get an idea.

At the moment the solar panels are connected in parallel (one group of 3 and one group of 2), 4 cables (2 positive and 2 negative, from the two groups) go down to the inside of the van.

I have been able to disconnect the cables of the group of 3 (and the charger charges at 25W) and if I disconnect the group of 2 and connect the group of 3, it charges about 35W. Each group give an open circuit voltage of about 19v.

The only thing I can think of is that a solar panel has lost performance, lowering the total voltage (being in parallel) and the charger has trouble finding + 19v (5v more than the battery) and does not just work.

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seb71 commented · Jun 26, 2022 at 05:32 PM

As already told, wire 2 or 3 panels in series and see how that works.

If this works as it should, then you have the option to make 2 strings of 2 panels in series and then put those 2 strings in parallel. Leave the 5th panel unconnected.

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SCC 100/50 low W-V

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