Nautitech 44 Open: Solar performance challenges and solutions

Andrew M
Sep 3, 2024
4 min read

The set-up

We opted for the solar package offered by Nautitech on our 44 Open Catamaran. This included:

4 X100W Solar panels mounted on the Dinghy Davits (400W)
4 X 180W Solar panels on the starboard side roof (720W)
4 X 180W Solar panels on the port side roof (720W)

In theory, this gives us a maximum potential generation of 1840W or a charging capacity of 108A at 13.3V.

The installation is very professional and it is looks really good.

For batteries we went all in:

3 X 340AH SuperB Lithium, for a total capacity of 1020AH

MPPT Charge Controllers

There are three charge controllers, one for each set of panels above
Nautitech installed Cristec YP080-12-40 MPPTs. These are each capable of delivering 40A at 12V to the batteries.

Wiring set up:

For each set of panels; Two panels are connected in series and then the pairs are connected in parallel.

Physical location of equipment

Finding all the pieces is a challenge as they are distributed around the boat. This is unfortunate as I think they could all have been installed under the port side rear bed! Also this is not documented, I had to engage our broker to find the pieces.

Batteries and Charge controllers are installed under the port side rear bed
Isolation switch for the davit panels is in the port engine compartment
Isolation switch for the rooftop panels is behind a panel in the port side rear cabin

Expected Performance

The theoretical capacity is1840W. Of course you cannot expect to reach this in reality, the horizontal mounting is not ideal, shading from the mast and boom, efficiency factors and losses that will bring this down. Also, as is standard practice, the charge controllers are derated. So while in theory the rooftop panels could deliver 720W, the charge controllers that are installed can only handle 480W. So the theoretical maximum that could be delivered to the batteries is 480 + 480 + 400 = 1360W, or 100A at 13.3V.

To get a more accurate estimate of what to expect NREL has a tool called PV Watts. This is a great resource for anyone who wants to understand what to expect from your solar set-up.

Here is a summary report for 720W panels assuming I am in Menorca: Report.

Now the summary is not that helpful, but you can get a csv download for each hour. This allows you to compare what you should expect vs what you are actually seeing.

Expected vs. Actual

Unfortunately the Cristec charge controllers do not have a Bluetooth feature or an App, so there is no way to directly see what is being produced. I use the SuperB battery monitor to determine the performance. My base Load on the batteries is -20A at 13.3V.

I did my comparison while all panels were in full sun at noon on 24th July.

Panels	Capacity	PV Watts Est.	Controller Limits	*Actual seen Super B
Davit	400W/30A	280W/22A	22A	-
Port Roof	720W/54A	530W/37A	36A	-
Starboard Roof	720W/54A	530W/37A	36A	-
Total			94A	50A

*Super B reading was +30A, add base load of 20A, means 50A was being pushed to the batteries.

Conclusion - I am getting about 50% of what I should be getting. Investigation

I checked the wiring, measured the string voltages and everything looked good.
I looked at the individual performance of the three sets of panels all were underperforming to the same extent.

The common component in this was the Cristec Charge Controllers. I checked the setting on each and they seemed to be the correct settings for my batteries. I concluded that the Cristec Charge Controllers were not performing to spec. Maybe they could not handle my 1000AH batteries.

I reached out to my broker and they reached out to Nautitech. Nautitech did not offer any explanation and made no attempt to help! Very disappointing. My broker agreed with my conclusion and agreed to swap out the Cristec Charge Controllers for Victron. Great service here.

I ordered the replacements and installed them. I went for higher performance ones so that the Charge Controller would not be a limiting factor. I intended to order the ones with built in Bluetooth, but did not read the fine print. I ordered BlueSolar, despite the confusing name, you have to buy a dongle to get Bluetooth! SmartSolar product have built in BlueTooth.

The Victon Results

With the Victron Charge Controllers I am seeing much better results. Under similar conditions to the above I am getting 80-90A. IE what I would expect. Advice for those who follow

The Davit mounted solar is the best as it is less prone to shading. Unfortunately Nautitech only put 400W capacity. It seems to me like there is room for more panels there without impacting the look of the boat. In fact it makes sense to have the solar panels to provide a "roof" over the whole dingy.
Go for bifacial panels on the Davits. They are much more efficient
Don't accept Cristec Controllers. Insist on a product that supports monitoring
Ask for test results before you accept your boat

I hope you find this useful. Please provide your feedback.