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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 ControllersMPPT SmartSolarSolar Panelsolar
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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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combatdiver avatar image combatdiver commented ·

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


Thanks!!!


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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 ?

Thanks


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seb71 avatar image seb71 commented ·

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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JohnC avatar image
JohnC answered ·

Hi @CombatDiver

There's a Victron browser-based calculator: https://mppt.victronenergy.com

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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combatdiver avatar image combatdiver commented ·

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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JohnC avatar image JohnC ♦ combatdiver commented ·

@CombatDiver

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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combatdiver avatar image combatdiver JohnC ♦ commented ·

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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JohnC avatar image JohnC ♦ combatdiver commented ·

@CombatDiver

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): https://www.victronenergy.com/media/pricelist/Pricelist_Victron_2021-Q1_Euro_C_.pdf


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combatdiver avatar image combatdiver JohnC ♦ commented ·

Hi JohnC

Amazing!!

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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JohnC avatar image JohnC ♦ combatdiver commented ·

@CombatDiver

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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combatdiver avatar image combatdiver JohnC ♦ commented ·

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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