combatdiver avatar image
combatdiver asked

Question regarding Maximum PV open circuit voltage for MPPT 100/50 SmartSolar regulators

Hi I want to update my solar installation. It is in a boat, alway anchored,so she is moving all the time around the anchor. Weather is always tropical, close to the ecuador

To update it, I though to set 2 solar panel, 450W each one, in series, 900W. Voc= 49.27 and Vmp=41,37 I want to use MPPT 100/50. If I set the panels in series, Voc total is = 98,54v. It will be 2 sets, 2 regulators, 4 panels, and total 1800W. If I use bigger regulators, I should go to 150/60, so I will double the budget, as I will have 2 sets

Please my questions:

1º - PV MPPT 100/50 limit is 100v. Can it be keep it below limit with stated above, keeping in mind that the PV would be always between 15ºC and 60, and I can assume that it will be some lost in 6 cable meters and joins?. And important too, in a boat, with my old installation, I never reached maximums, as the boat is always moving around the anchor, so there is no a optimal and fix orientation towards the sun, and there are some few objects (mast, aerogen, radar), which cast shadows to the PVs?. E.G., in my old I have 500W, but never got more that 340W( 14vx24A), with sun at zenit

2º In the same way, what is the tolerance +/- of the 100v limit for the regulator? Within the manual, there is nothing about it. I meant, if the real limit is 120v, it will be safe I guess.

3º Can I put in paralell the 450w PV increasing AWG cable but lowering the max voltage? I guess in a MPPT would be not suitable do that?

4º Can I set a voltage limitator for 100V just in the inbound of the regulator?. Maybe some kind of varistor.

5º I tried to use the victron excel tool, but I couldn't as per there is some problem if you open it using open office (xlsm format), and I cant use with excel 2003. I tried with opencpn, but it was overflow (value!), when I tried to set parameters, and a new PV , custom. Any idea?

Thanks for your time, BR

MPPT ControllerssolarSolar Panel
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4 Answers
wkirby avatar image
wkirby answered ·

You did not mention your battery Voltage, this is an important factor to answering some of the questions.

1) It cannot be guaranteed that the PV will not go over 100V when its is so close to the limit already, even when hot. If all things align, the boat swings into a position causing no shadows and then there is also a cloud edge effect, then for a moment the PV Voltage can go over 100V.

2) The 100V limit is a hard limit, no tolerance here. You have to design the array to keep below this.
The limit is imposed by the transistors inside. 100V transistors are one of the common Voltage limits.

3) If your battery Voltage is 12V, then yes you can run two panels in parallel. Run the cables directly from each panel to the MPPT for two runs, maybe cheaper than a single run of different thicker cable plus combining. I like to advise a fuse in each parallel run.
For 24V battery, this combination should also work because those panels are relatively high Voltage. Maybe not as good production for 24V battery on cloudy days.

4) Maybe possible, but no supported answers here. Also the reliability of such a solution is questionable.

5) The spreadsheet calculator only works in Microsoft Excel. I am also an Open Office user so I know this problem.

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Only one thing I m re-thinking.... If I put the PV in parallel, the Imax from PV, (I don't know the parameter name), I guess is 2(2 pannels) x Isc = 2 x 11.53A = 23,06A.

With this and If I am not wrong according the 100/50 datasheet, maximum is 60A, so I guess I'm far away for this limit.

But this input will generate surelly 50A output, that is the max output in the regulator

So, by any chance can be the regulator jeopardized to be working a few hours every day at full output? By the time, my answer is that when there is too much input in PV side, the regulator just take it as much as it could but not more, right?

Thanks again

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combatdiver avatar image
combatdiver answered ·

Thanks wkirby for your quick , fast and accurate answer

Sorry I forgot most importat!, my system is 12v

Clrystal clear your answer. I guess my option is to use the parallel if there is no counter-issue on that

Hope Victron, can create a new regulator between, as for my options is or 100/50 or jump to 150/60, and price is double, or downgrade my PV to 1400W instead 1800W


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combatdiver avatar image
combatdiver answered ·

Just 2 things I'm not sure of:

1º- As I said, the 60A limitation for PV inbound to the 100/50 regulator, to have these 2 PV pannels in parallel, I will get around (max) 22A, so it is ok in this set?

2º- I found other option. Place 1 regulator 150/100 instead 2 100/50, and put the 4 PV with 2 series in 2 rows(parallel), all to the unique regulator 150/100. The PV voltage limit is not exceed as it will be 100v , below 150. As the PV plant is 1800w, with 150/100 I will have still output limited to 1450W, but doesn't care. Cost of that regulator is simillar of 2 of 100/50. I guess it could work...Am I missing something or there is another limit ?


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Be careful with series panels. If one panel is in shade, the entire string will not produce anything.

Also, will all panels face the same direction? They should, if connected to the same solar charger.

Do you already have the panels?

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Hi Seb71. First, thanks for your commends, I really appreciated

Not the entire panel will be is shade, but some of the cells can be ( boat higher elements, like a aerogen, the boom, or rigging wires will cast shadows putting a few cells off the sun, but still working). Can it be a 10% of the surface at most, maybe less. Can it involve a 10% in the no shadowed serial co-partner pannel ? Why? the total current incoming to the regulator is always the lowest among the couple?

As I said, this is a boat. The boat is always moving around a center point (anchor), so the orientation is not the same, and depends on there is blowing the wind and where is anchored the boat. Most of the time, the wind will blows from east (E), and we will be in the north emisphere, so the boat will be oriented with the bow to the E, but I will put 1 of the series pannel NS oriented, and the other EW oriented. The other series the same.So 2 panels in diferent series will be along the track of the sun, and the other pannels in different series will be with the short dimension oriented to the track of the sun. Anyway I wanted to place the panels in a maner that the diferent orientation of the boat will not be a diference between 2 groups ( 2 panels in a regulator, other 2 in the other), in a maner that maybe in one regulator will coexist one along (2 m) an other with the short part (1 m).

Still not buy anything. Just in pre-sales stage. But I want a 450w panel 1x2 meters WxL, 4 in total


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The cells in the PV panel are wired in series. If a cell is shaded, the current from that cell drops. Because the cells are in series, the current from the entire panel will drop. Another panel in series with the shaded panel will also have a current drop because of that.

You can test this with your old system.

When I said that all panels connected to a single solar charger should have the same orientation I meant all to be in the same plane. If the boat moves, they will remain in the same plane.

I will put 1 of the series pannel NS oriented, and the other EW oriented. The other series the same.So 2 panels in diferent series will be along the track of the sun, and the other pannels in different series will be with the short dimension oriented to the track of the sun.

If I understood correctly, this arrangement definitively requires two solar chargers.

If you want to wire the panels in series, then also look into 60 cell panels and how can you fit/arrange them on your boat. Normally these have lower price per Watt and with 60 cell panels you can use 150/xxx solar chargers (with 3 panels in series). So check if you can fit six of these 60 cell panels instead of four 72 cell panels.

60 cell panels are just under 1m wide and about 1.65m long.

Also can't you change to a 24V system (24V battery)? It would be better suited for that power level. And if you plan to expand, even 48V.

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Thanks again Seb71

Ok understood about the series. Crystal clear!

Thanks for your commends about the 60 cell panels. I will think about it.

I checked that 450w panels, has No of cells 144 (6×24), 2mx1m. Seems 6 paralel of 24 in series.

I guess if I use a 150/100, I can use 4 PV 450W, (Voc=49v), if I put 2x2, 2 PV series in 2 rows parallel. The max 1800w power, will be cut up to 1450w, that only one 150/100 will manage. That's I guess, with this 2x2 layout ( 2 rows of 2 series), to only one regulator, will manage with the shadow issue, keeping in mind there are 4 panels, with serial-parallel each.

I wanted to say also that the 100A that the output in 12v system, is maybe double that my loads needs ( charge the batery and 2 refrigerators, 4A per each). To Have 50A more , they are for future purposes ( maybe start the watermaker not all the days), use electrical tools seldom, and try to cook a 1000w in AC cooker or a electrical motor in the shaft (experimental)

I don't expect even with 1800w to have all 1800w, based on the experience I have with my theorical 500w of old pannels, because I never saw more than 25A output to 12v system, that's with supose 14v, this is around 350W, so the 75% of the theorical 500W. At least in this area Central America Caribbean, in a boat.

The other option the supplier gave to me ,1,66x1m, 345w, No of cells 120 (6x20), seems 6 parallel rows, of 20 in series. This last fits perfect to 100/50 regulators, and power 1400W, Maybe it could be the better choice..

These panels are PERC (Jinko), seems good, and low price, 169USD per unit. That's why I wanted ... but maybe you can say something about it

By the moment, I can't affort to change to 24v system. Almost everything need 12v, as this is the standard in boat industry, although there are other devices that I know they are dual. And I guess , I have to wait to do so when my old bateries will be down, and I will install new bateries and change all the wiring to adapt to it. I guess now I can not put my old bateries in 24 bank, just a thinking, maybe someone can say that it will be good for them¿?

Thanks again

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Both those panels (the 450W and the 345W) are "half-cell" type.

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And , what does it means that? , half-cell type has something to be aware about?


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Those are panels with cells cut in half and then wired in two groups (somewhat similar with two smaller panels/modules wired in parallel).

There are advantages and disadvantages. Better read about them and make your own conclusion.

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Ok thanks!!

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Ok thanks seb71. Finally I will put one 450w connected to its own Mppt 100/30, having 4 mppts and 4 ,doble or half Pv each one with 6 x 24 cells. I assume with this set, I will be avoiding/isolating/limiting as much as possible the shadow efect as the impact that this has in every serial versus the others. Thanks

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JohnC avatar image
JohnC answered ·

Hi @CombatDiver

There's a Victron browser-based calculator:

Be strict with the data (especially temp) you feed to it, and don't attempt to rationalize poor light as a reason to stretch the recommendations. You'll come unstuck, as high panel V's can be reached easily when no current flows/poor light. And that can happen too when the mppt periodically scans.

Even test 1x mppt per panel if you have selective shading. You can downsize the mppts if you don't expect to utilize the full power.

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Hi JohnC

Thanks for your comments

Ok, I will keep in mind your remarks. Actually , I'm thinking to take only one 150/100 regulator for the whole 4 panel instalation, and set 2 series in 2 paralells. So I guess I will overpass the V max problem

The point is for 12v, there is no more that 1450W regulator possible, or 2 regulators, with this V oc and power. But ..besides:

1º -I don't need 1800W, with 1400W I'm fine

2º - But, as I'm in the tropic, half of the year is raining, half shining. Besides the movement of the boat and the small cast shadows, I thought It will be a good idea to oversize the panels, in order to harvest more power even with low sun codition.

3º - I checked also that the regulator can handle the max power and limit it with no problem, although the Vco should be observed, the max output will be limited, and in the even of the Ioc will be reached at full in all the panels, the max I input will be not reached

So that's why I choose 4 450w, total 1800w, not less. Also because I'm thinking to update the plant in a future, but not sure, so I could change to a 24v system when my bateries would be dead, so I will take full advantage of 1800W, or even add more panels and with other regulator of 150/100, I will get all

Maybe you can tell share me your thoughs about it?

Thanks a lot

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I'm all for 'overclocking' the panels to allow for bad weather. Within the guidelines of course. Go for it.

But don't underestimate the effect that shade can have on panel output, even a shadow from a wire on one panel can devastate the output from that string. And depending on the characteristics of the panels, the Vmp may become different between strings, and the tracker mightn't find a common optimum.

I don't mind a gamble myself, but only you can judge the odds in your own situation. I wish you good luck with your choice.. :)

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Hi JohnC and thanks again. The shadow efect you said, can explain why my nodaways pannels are outputing 340w at most, when it should be close to 450w, that they are rated. This is 75per 100. Can also explain my feeling that why at the begining I got more power when the windturbine was not installed. Anyway I got max 24A in 12vdc, and the regulator is rated 30 max.

I have wires , windturbines and radar radome... and the incontrolable movement of the boat wirh wind at anchor which makes this more dificut. I can not get rid of these. I will got your advice, thanks.

For your comments, I should use a 2 series 2 pararel with one regulator, to dilute the shadow problem. Or use 2 regulators each one with 2 paralleled PV, avoiding serial

thanks again

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The second option with avoidance of serial stringing would likely be favoured there for shade management.

The 'best' option might actually be a 100/30 on each 450W panel, and many people do this. Well matched and max potential, but the extra wiring/isolators/space might put you off. There shouldn't be much difference in the cost of the blue boxes though. Retail pricelist for comparison (in Euros, sorry):

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Hi JohnC


I have peregrinated through 2 100/50, 1 150/100, 2 150/70 and.... you click right in the middle!!, Yes! to re-use my actual 100/30 and buy 3 more, and set every one with every PV!! Thanks a lot

And I will have 4 system redundancy. The price of 2 150/70 are above than 4 100/30.

I have to see to the details about to wire x4 and space by 4 regulators . So I guess this is also the best approach for the shadow problem?

Thanks for all, and also for the price list, it is very usefull!!

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Yeh, it's the ultimate approach for shading issues. I've pointed out the downsides, but one consolation there is that multiple blue boxes look great on the wall. Like brushstrokes on a Van Gogh, heart gladdening.. :)

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Ok thanks.After a long long period of decision making time, I got your answer as the winner. At the end, 4 of these 100/30 are cheaper than other options, and most reilable. Hehe I will think in Van Gogh every time I open the rack and see them. Hope I can get all the info colected in the same app, not to check every mppt. Thanks my friend

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