Matching Victron solar controller

[g550]

Hello to everyone.

I am a bit confused about MPPT Victron controller matching.

At the moment I have two 100W solar panels in parallel charging 12v house batteries thru PWM controller.

I would like to upgrade to 2 x 250W panels in series thru MPPT controller.

Question:

Which controller do I need if i run both panels in series providing 250W 24V to the controller. I understand that the MPPT controller can convert 24v to lower voltage which is needed to charge my batteries.

Do I need 100/30 or 100/50? or may be even a cheaper/smaller one... Victron smartsolar 100/50 is 325 Euros.

is there a controller which will provide me with what I need for less money?

Thank you all.

[noelex 77]

You need the 100/50. The 100/30 will not be damaged, but the total output would be less.

An alternative would be two (one for each panel) 100/20. This is likely to be cheaper (although I have not checked the retail pricing). This option will provide slightly more total power and have redundancy. The drawback is slightly more complicated and expensive wiring, as wires from both panels need to led back to the controllers.

[gmakhs]

Buy the 100/50 and use the panels in series performance is delightful.
You can find cheaper China mppt but most of them can't handle over 36 volt ....
If you want to save money buy 2 pmw cost 15 euro each and connect every panel seperately.
Mppt work well in a boat because it performs better understand shadow ( higher voltage because panels are connected in series)
P.s I made a test on victron energetic 75/15 with 1 solar 100w or 2 solars 50 watt on series , because of the higher voltage output of the two solars you get more power and sooner in the day .

[noelex 77]

Originally Posted by gmakhs

P.s I made a test on victron energetic 75/15 with 1 solar 100w or 2 solars 50 watt on series , because of the higher voltage output of the two solars you get more power and sooner in the day .

Interesting. The Victron controllers do have a very high (+5v) start up requirement and there is some concern they may start up late in some situations if teamed with a “12v” panel or panels connected in parallel.

More details would be great.

[gmakhs]

The panels are connected in series so the max output is 36 volt .
With one panel is 18

[noelex 77]

Originally Posted by gmakhs

The panels are connected in series so the max output is 36 volt .
With one panel is 18

Understood.

Solar panels produce lots of voltage before they can deliver any current, so normally upping the voltage by connecting the panels in series does not make much practical difference to the production at the start of the day. Any slight gain is swallowed up by the poorer performance of panels connected in series when subject to shadows. Hence the normal recommendation to connect the panels in parallel rather than series.

However, the Victron controllers are unusual and will not start until the panel voltage is 5 volts over the battery voltage. There is some concern that in some conditions the Victron controllers could wake up later than they should when used with a “12v” panel.

If you have found evidence of this happening in practice it would be great to hear some details of how the comparison was done.

[john61ct]

The 75/15 SmartSolar is maybe $120 and IMO perfectly matched 1:1 to a 250W panel.

The tiny bit of output sacrificed by such overpanelling would only be in very rare moments of peak output, and the **average** output per SC$ greatly increased.

Plus each panel gets its own MPPT optimization, and unbeatable handling of inevitable partial shading.

Ideally the panels would be rated 40-65Voc to give the MPPT greater headroom, but if 12V nominal, over 20Voc should be fine.

[Hickers]

2 345 watts of sunpower panels gives me 50 amps from the 60 volt supply via the 100/50 Victron. I would have been better off with the next size up. Some days I make 3 kw from my 2 panels. This setup has cut our genset runtime in half.

[john61ct]

To clarify my above reco, I am advising against serial-connecting panels, especially on a sailboat.

Buy a higher Voc spec panel to get the better MPPT performance.

[conachair]

Originally Posted by gmakhs

The panels are connected in series so the max output is 36 volt .
With one panel is 18

Sounds very low, is that open circuit voltage?

You lose next to no power waiting for the victron to turn on with a 36 cell panel, if it isn't light enough to push the open circuit voltage above 18v then there's not enough power to push any current into the batteries.

If there's a chance of one panel getting shadow then parallel is probably a better bet otherwise the power from both panels can get hammered by a shadow on one.

[gmakhs]

The open circuit is 20 , I don't remember exactly now , both panels are mounted on a arc next to each other , I do believe series is the best for shadowing , but I haven't test it , I have test only with shading from clouds (low light conditions )

But I might be wrong as well .

[conachair]

Originally Posted by gmakhs

, I do believe series is the best for shadowing , but I haven't test it , I have test only with shading from clouds (low light conditions )

But I might be wrong as well .

Plenty examples on youtube....

https://youtu.be/kHafdxzIMh4

[CatNewBee]

Originally Posted by conachair

Plenty examples on youtube....

https://youtu.be/kHafdxzIMh4

go parallel, if possible, use larger panels / high voltage panels with more cells.

[john61ct]

Originally Posted by gmakhs

I do believe series is the best for shadowing , but I haven't test it

No that is 100% false.

Diodes can mitigate but have their disadvantages.

Best on a boat to get panels already in the voltage range you want rather than wiring them in serial to get there.

[daveNZ]

I’m getting nervous about a Victron mppt solar regulator 75/15 I have just bought for a 150W 17V Pmax panel.
so the reg. needs batt+5v to start! can you trigger it by turning on some load to lower the batt. voltage? e.g. turn on a pump.
How long (milliseconds?) at batt+5V does it take to get the Victron reg.started?