I had recently the following installed on my boat (Sydney, Australia): 3 Victron solar panels 215W each, Victron Multiplus charger/inverter 3000W, smart solar regulator, battery monitor.
I wonder what kind of output I can expect under different scenarios. Currently I don’t get more than 10 to 12 amp output on a reasonably sunny day, looking up the history via the app I see 435Watt max on a very sunny day, but mostly around 230W or less.
Although it is partially cloudy, I had expected a lot more and the system can hardly power instruments and fridge…
Installer will come back and look at it, but I would like to understand what reasonable expectations would be.
You can have a look at the Victron MPPT calculator and put in your panels and location. I had a quick look and this suggests that for May in Sydney you will get around 1.9kWh over a whole day, assume 6 hours then that is an average of 1900 / 6 = 320W or there abouts. Depends if you get any shade on the panels. It also depends on what MPPT has been fitted, hopefully a 50A unit, but if the installer has skimped then a 40A unit will restrict the peak power. If there is some shading are the panels in series or parallel, parallel may be better for partial shading.
There are other on line calculators if you search that will predict the power over a day rather than the total energy per day.
Thanks for the comments. The regulator is a MPPT 100/50. The panels are at the back of the bimini, so no shading. As a test I left the instruments and fridge on when leaving the boat last week. Two days later the batteries were down from 92% to 54%. The two days were half cloudy/half sunny. Given that the instruments were in ‘passive’ mode, this means that had I gone out sailing, with autopilot on etc, I would have had to run the engine to keep the batteries charged. On a previous boat a 135w cheap flexible solar panel kept the batteries charged under similar circumstances, so I am rather concerned.
If you czn grab some screenshots ftom VictronConnect when charging showing the performance, history and settings pages we might spot something amiss. These can also be accessed remotely if you have an Internet connected GX device and VRM. Most issues are normally wiring, connection breaker related causing resistance, voltage loss and limiting the current.
Presumably your panels are connected in parallel because a series connection on those panels would exceed the 100V input limit?
Victron datasheet for their 215W panels says optimum operating parameters are around 40V and 5.4A per panel.
For a parallel connection with those panels you could be getting up to about 16A with three in parallel. Check connections to ensure all three panels are connected properly. If one of the panels is partially shaded or has a poor connection it could explain your results. Wiring path length to all three panels (and back) should ideally be roughly equal because with either 4 or 6 sq.mm PV cables at around 5A per panel there will be some volt drop in the cables and a path length mismatch will inhibit output of the one with the most resistance.
Orientation to sun is another factor. Southern hemisphere going into winter. You are quite far south in Sydney. If your mooring/anchorage affects orientation or results in shading by other vessels then performance will be affected.
@Boonteller just to add to what has been previously said, May in Sydney is not the best for solar yield with the Sun having a maximum altitude on say, May 14 of 38 degrees.
The yield from solar panels follows a SIN rule so assuming the panels are horizontal, the maximum yield for the panels for tomorrow will be 3 x 215 x SIN 38 = 645 x 0.615 = 396 Watts. I assume the system is 24 volt (Let’s assume terminal voltage of 26 volts) so the very maximum you will ever see tomorrow out of your panels when the sun is at its very highest point is 396/26 = 15.23 Amps.
If the sun is low in the sky unfortunately the yield reduces significantly.
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gain: many thanks for the comments, it is slowly starting to make sense to me, but I still have questions about the performance, if I may. The panels are in paralleI, 24V. Battery banks are 12V, with a 450amp house bank. I have the bluetooth phone app connection, although the installer erroneously installed the BMV702 and not the 712 - which he will rectify.
I understand 24V panels for a 12V battery bank make sense due to better efficiency. I would expect 645W panels to theoretically yield around 50 amp (if they were 12V) and I assumed the same to be true for 24V panels with a smart regulator. Otherwise more efficiency with halving the output doesn’t seem to make sense - unless I display my ignorance with this comment…
I have attached pictures of the panels and the various components and rad-outs of the app.
Various observations: bulk charging whilst the batteries are 100% charged strikes me as odd. On shore power it drops to floating charge. There doesn’t seem to be a clear relationship between the charging showed on the app and on the BM. Finally, I boiled a kettle of water via the inverter and brought the charge level down to 94.6%. There seemed hardly any increase in amp output/input, in fact the 1.16amp om the BM display is somewhat worrying. With a simpler system on my previous boat the charging would jump from around 1amp (floating) to 6 amp under such circumstances.
The uploaded app screenshots show the charging, history and some settings.
A couple of answers as you are clearly new to this.
- Bulk charge does not relate to the status of the battery at all, Bulk charge means that the charger is providing as much current as it is capable of, so if you have a 1 Amp charger and even if the battery is close to full, the charger can only output a max of 1 Amp and if the voltage is less than the absorption voltage and it is providing 1 Amp then the charger is in Bulk. In your case, because your solar system is only providing 2 or 5Amps in the screenshots it will show Bulk even if the batteries are close to full.
- Your have what you call 24V panels, this is fine, the MPPT converts the low current at high voltage efficiently to high current at low voltage. I have 680W of panels on my boat with a 150/60 MPPT, the panels often run at between 60 & 70V producing max 10A and this charges my 12V batteries at 14.0V and max 50A, 680W. I normally see mid day in the summer of around 500W with flat panels on the top of the cabin in the middle of the UK, yesterday, bright sunny day 450W.
- I note in your photo the thin shadows from lines on the panels, these will degrade performance, how much I can not say.
Looking at your data.
- The MPPT appears to be working fine, on average your daily yield is lower than the MPPT calculator, but I have no idea if that is based on flat panels or not.
- The normal problems we see with wiring would cause the battery voltage or panel voltage to be at extremes if it was working but these look OK.
- 8 days ago you had a peak power of 469W so the system appears to be working and it got up to absorption voltage.
- Since then it has not has as good a day, had the weather deteriorated or has something else happened to drop off the production.
- You are showing some very low battery voltages, do these occur when you have a high power draw on them or are they getting this low with little power draw. If it is while there is little power draw then you have aged batteries.
- You are clearly using more power than you are generating over the past 4-5 days.
- I can not diagnose any further, the only thing that would fit is if one of the 3 panels was not producing as much as expected or there was some extra resistance in the cabling between the panels and the MPPT. I see you have resettable breaker, often the DIYers use cheap low quality items that have poor contact resistance and cause problems, hopefully a professional installer is using a good brand such as BlueSea.
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In the original post it was stated that 3x Victron 215W panels were installed in parallel.
The Victron datasheets list only one panel with 215W rating; this is a monocrystalline panel with peak voltage of about 46V and a working voltage approx. 40V.
However your MPPT charging history is showing incoming solar voltage peaking up to 71V.
Maybe your panels are different from the datasheet I looked at. Could you possibly provide a pic of the data plate under the panels or an exact model number so I can confirm.
Reason for asking is that if 40V panels are producing 70V then at least two of them are in series connection and this could explain the lower than expected solar yield.
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That is excellent observation, 2 in series the other in parallel would only produce from 2 panels. I do not believe all 3 could be in series (at the 40/46V) as it is a 100V MPPT.
Thanks for picking this up! I was at the boat this morning and made a pic of the data plate. Surprise: they are not Victron 215W, but Exotronic 225W (pic attached). I haven’t spoken with the installer yet, but I think he may have had a valid reason for not installing what was quoted. They are locally made, not cheaper than Victron, and Exotronic uses Victron MPPT, chargers etc and bluesea accessories, so perhaps Victron panels weren’t available (we have occasional supply problems down under).I will ask, though! Another somewhat embarrassing fact: there are two small spotlights each side of the bimini to assist with evening/night docking. I can’t see them unless standing very close at the side of the boat, which I rarely do.Not visible (in daylight) from the boat, so i only noticed this morning, when hanging of the stern to photograph the underside of the panel, that they were on. Perhaps drawing around 4amp. Installer had switched them on, it is a previous owner’s install and you can’t see if they are on or off from the cabin either (push button).
That still doesn’t explain, I believe. the very modest charging…or does it?
As to the questions from @pwfarnell: 3 and 4: 8 days ago was an exceptionally warm and sunny day, weather has deteriorated since, with the occasional half-sunny day. 5: low battery voltage: I did draw a lot of power twice (2200W via inverter) when boiling water with an electric kettle to test how long before full recharge. Batteries are about 4 years old.
Thanks for the pic. Voc 24.3V and Vmp 20.4V so based on the PV input to the charger they are in series and in direct sunlight you could see a charging current of around 11A. Series connection means that a shadow falling over any one panel can interupt the whole string.
Even a thin shadow from rigging lines can do this. Parallel connection in the same situation would only interupt power from the shaded panel/s. However the voltage of these panels is not enough to charge a 24V system when wired in parallel. Changing the panels out for the originally quoted Victron units may give you more flexibility but its a tough call.
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So the panels will be 3 of those in series to match the observed 60V to 70V. This makes sense.
The fact you are getting the correct voltage means the panel install / wiring looks OK.
The only comment I have is the panels being in series may be more prone to shading effects depending on how many bypass diodes are fitted. With the higher voltage Victron panels they would have been parallel wired. With these parallel.wiring would produce higher current.
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Thanks very much all contributors for the expert advice and assistance. Its a steep learning curve…but all very, very helpful. I have hopefully some ammunition to discuss matters with the installer.
Here is a solar calculator that will use average solar radiance. I chose Sydney, 0.675kW of flat panels and for May it predicts average of 42kWh for the month so a typical day is 1.3kWh.
The next site gives state wide history and says NSW would peak around 40 to 50% of rated install, so 300 to 350W. With a postcode you can refine this.
Your peak powers look OK vs the history but production is down vs average which may just be cloud, but could be an indication of shading at certain times of the day.
Very interesting sites, thanks for the links! I am just wondering how performance for solar on boats compares to that on houses (which is what these sites are measuring). I looked at ‘my’ postcode area (20xx): it has a seriously dismal performance compared to adjacent ones (who are still not very good). I suspect that the fact that many houses are in areas with a substantial tree canopy of non-deciduous trees may affect the figures. Apparently there is a relationship here between socio-economic status and uptake of solar installations on the one hand, and ‘tree-lined streets’ and socio-economic status on the other hand. As boats tend not to be located under or close to trees, by what factor should the performance of solar panels on a boat have to be multiplied, if at all, to arrive at a reliable figure? I attach a pic of what a typical tree canopy looks like, even in winter (very cloudy day today!). Interesting anyway and I’ll use this info for some further research into this.
If your wiring from the MPPT to the solar panels is good for 30-40A 6mm2 or larger. You could try parallel them with a 3 x y cable I have a link from amazon. That will help if you have any shading.
I currently have 4 heavily shaded 100w panels in series getting about 1.2-1.3kwh a day. I am going to try 2P-2S tomorrow and see how it goes. The sun is getting lower atm coming into winter. I post tomorrow for you if it improves. My system is 24V not 12V so I cant parallel all 4 but I might and connect it to my 12V system.
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I had a marginal improvement using 2p2s configuration today. The shading power loss was reduced slightly. There were no clouds and few yesterday.
Hi Edward,
I see you’re in North Harbour. I’m in Pittwater so a good comparison.
From experience, flat Bimini-mounted panels will have poor yield from May through to September with the sun angle.
Additionally, as you’re on a swing mooring, you will get shading from the mast. As your panels are series connected, shading of one panel will compromise output of all panels.
The last month we’ve had a fair amount of light overcast, which will also compromise output.
I have two 415w panels on a boom awning (yes, it’s big). I have put each panel on its own controller, with a mast-shadow-width between the panels, so if I’m swinging on anchor when out (we’re in a marina), bow into the sun, shading will only take out one panel’s production.
When your installer fits the BMB712, make sure he networks it with the controller.
My best recommendation is to perform a power audit; start with fully-charged batteries and decide what loads you want on - fridge, etc. Record your 24hr consumption and then note your daily production. In lieu of increasing production, limit your loads to what you can comfortably put back in.
Happy to catch up in person to discuss if you like.
Regards, Gary.