How to setup Panasonic solar panels? Step by step, calculations, measurments

June 4, 2020

Back in March last year I purchased two Panasonic solar panels from Midsummer Energy. Each panel has a maximum of 325 watts, 57.6 volts and 5.65 amps. They’re quite large at just over a metre in width and one and a half metres in length. Even though my narrowboats roof has just over 16 square metres of available space, I needed to take a number of things into consideration before I decided where to mount the panels. I have a multifuel stove chimney, tv aerial and mushroom vents all getting in the way. The biggest issue for me was to have the space from the rope eye in the centre of Alice to the stern free as much as possible, to avoid my centre line ropes getting tangled up. Also, Photovoltaic panels work most effectively when the maximum amount of light particles from the sun hit their cells at a perpendicular (90 degrees) angle. The difference in output between flat and angled panels can be as much as 20%. This was the difference at various angles this evening. I decided to use these angled brackets to mount my panels.

I decided to mount the panels at the bow of Alice either side of a mushroom vent. I drilled holes on the side of each panel into the aluminium frame. I added standard M8 bolts, washers and nuts. Forward wind a year and the fact I didn’t use stainless steel is clear to see. So take note and install stainless steel bolts that don’t rust and require extra hassle and work later on. I fitted the brackets to the solar panels and lifted them onto the roof of Alice to measure up. After positioning and standing back and checking from the stern, and from the sides I marked where the holes of the brackets would be and got to work making 8 holes in the roof! Once I had drilled the holes I tapped them so I could screw the bolts straight into the roof without the need for nuts on the underside. I added lots of Sikaflex to the underside of each bracket and positioned the brackets and screwed them on firmly. I will be taking the panels and brackets off the roof when it’s time to paint Alice.

I had solar panels with MC4 connectors. I decided to connect the panels in parallel to avoid shading on one panel, bringing the whole power output down. I used two 4mm cable branch connectors. One for the positive and one for the negative. 4mm double insulated solar cable was then taken in through a mushroom vent to the stern of the boat where my battery cupboard is located. When I paint the roof, I will feed the cables in via a dedicated roof cable gland. I have a Victron Smart Solar MPPT 100/50 charge controller. This has Bluetooth built in and I can see live, the status of what solar is being produced on my mobile phone. The MPPT monitors the solar voltage and current and constantly ensures it’s getting the most from any available light. Before the MPPT I have added a Blue Sea 300 amp switch, so that I can completely isolate the panels if I need to. It was then time to connect the solar cables and the battery cables to the MPPT. Although the sockets on the controller were the screw type that clamps the cables, knowing vibrations can affect these types of connections, I once again used ferrules on the ends of all the cables to form a solid and secure connection. I used a Dymo, Rhino 4200 label printer to identify my wires. It not only prints onto stick labels I used on the larger battery cables, it also prints onto heat shrink. I printed off a series of heat shrink labels and along with the standard red or black heat shrink, I shrunk them in place.

This created a neat, labelled and secure cable ready to connect to the MPPT controller. Using the Victron Connect app on my phone I connected the MPPT using Bluetooth. The app informed me there were more up to date firmware and Bluetooth versions available. I simply pressed the update button for both and they remotely updated the controller. I clicked the cog at the top right to set up the controller. Next, I clicked the Battery link. I made sure the battery voltage was set at 12 volts and using the drop-down menu, I changed the Battery pre-set to Lithium Iron Phosphate (LiFePo4). This set the MPPT with the recommended settings from Victron. The absorption voltage was set to 14.2 volts, maximum absorption time was 6 hours. Float voltage of 13.5 volts and with no equalisation. If you’ve watched any of my previous lithium battery videos, you’ll know the system has a battery management system. When the BMS is happy, it gives a positive signal via it’s charge connection. You can use this to simply turn the MPPT on or off automatically using the VE.Direct non-inverting remote on/off cable. This is a nice and simple solution and all it would take is for the connection to the battery bus bars via a fuse and job done. However, I wanted to use the single VE.Direct port on the controller to send solar information to a Victron Color GX display that in turn uploads all the data online. There isn’t such a thing as a VE.Direct splitter so I could’ve only have one or the other. This is where the additional time spent testing came in and hence the delay in this video.

I knew I needed to interrupt the supply of power from the MPPT controller to the batteries bus bars. This needed to be automatic using the BMS in an over voltage situation. I initially purchased a Victron Cyrix-Li-Charge relay to automatically stop the charge. It seemed to work exactly as planned. As the relay has inbuilt intelligent technology, it cut the relay at night or when there was significant cloud cover. You would think that’s fine, however the constant on/off of the MPPT, caused the Bluetooth to randomly stop working and some days I’d be able to see the solar information in the Victron Connect app and others I couldn’t. So I needed to look for another disconnection method. I chose a simple on/off 12 volt 100A contact relay, again with 6mm bolt connectors for the solar cables I’d already made up and spade connectors for the supply. I wired it up and nothing happened. The relay just wouldn’t engage. I measured the amperage from the BMS and found although the positive supply for the load disconnect was 2 amps, the positive supply for the charge disconnect was 100 milliamps. Not enough to engage my simple relay. Now, finding a relay that had contacts over 50 amps but with a coil of less than 100 milliamps was very difficult. They are available but boy they are expensive. I wondered if I could use a Victron Battery Protect but in reverse. On the last page of the Battery Protect data-sheet, there was the diagram I was looking for. When using the battery protect in Li-ion mode it acts like a simple relay but with a tiny 1.5 milliamps when operational.

So I replaced the coil relay with the battery protect and connected the positive feed to the screw terminals. I fed the positive from the battery BMS to the green remote of the two pin connection and a negative feed to the middle of the green three pin connection. I then programmed the battery protect, using the LED display to 8C. This is Li-ion mode. If the remote power is cut as when the BMS senses an overvoltage, the battery protect stops the connection between the two screw terminals. This has worked flawlessly including the problem with Bluetooth. I have my lithium inside my boat in the warm but if you were to install the batteries in a cold engine bay, Victron have now introduced a way to stop the charge when the batteries are below their recommended 5 degrees Celsius. When using lithium its recommended to use a BMV-712 battery monitor, as this uses very little current. This battery monitor has a connection on its rear to connect a temperature probe to the batteries. Both the battery monitor and the MPPT can communicate to each other via a recently introduced VE.Smart network.

At the bottom of the settings page, there is the VE.Smart Networking tab. If you click this tab you can create or join a network. As I’ve already done this on the battery monitor, I clicked join existing, chose the already set up network and it connected them together. I haven’t used the temperature connector on my battery monitor but if I had, it would show up here and communicate it’s temperature with the MPPT. The 625 watts of solar has produced just over 325 kW of power during the past year. August being the highest at over 60 kW and January being the worst at 9.48 kW. Remember these figures aren’t what the panels can do, but what they have generated for use. So when I’m moving, the alternator will be charging the batteries and so the solar is not required and therefor, it won’t be shown in the stats.

I’m really pleased I got them and it is great being able to look at how the panels generate clean and efficient energy.


 

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