Updating the Solar System

The Solar Problem

When we purchased Eximius, we were told that the Solar Panels were a total of 350Watts with 2 x 100 Watt panels and 1 x 150 Watt panel. The solar charge has never lived up to expectation, and I wondered why!

My first thought was that the supply wires from the panels to the solar charger were undersized and that we were experiencing voltage loss over the length of the wires.

The wires are twin 10AWG and length is approximately 24’ one way, or 48’ round trip.

Looking up in the electrical tables for the voltage loss over that length of 10AWG cable I found that the resistance of that wire is 48’ x .102Ω/100feet = 0.049Ω≈ .05Ω

With the panels connected in Parallel, the max current would be about 15amps

Voltage Drop, Vd, = I x R = 15amps * .05Ω = 0.75v

That's not a huge voltage drop but more than I would expect.

The Solar Panels are mounted on top of our Bimini so we cannot see the underside of them, and we didn’t think to take pics when we had the Bimini off a year ago for restitching. I took photos this week.

The panels are not 350Watts!!!!

We have 2 x BP365U solar panels which are each 65watt panels and 1 x ICP SolarTech 100w panel.

So total wattage would be 230Watts and that was when new, which seems to have been in 2003. They have a 25 year warranty of 80% nominal output. So realistically, we have somewhere between 180watts and 230watts.

So taking a mid point on the 17 year old panels, let’s say we have 200 watts. The panels in parallel should have a voltage of 21v and max current of 14amps. So my calculations above would seem valid.

We have a Blue Sky 251 2i Solar Boost MPPT Controller. Which has a 25v, 25amp capability. Which would seem very capable of handling the output of the panels and the battery charging.

Oh, the Batteries: We have 4 6volt Trogan 105 Batteries connected in series and parallel to provide a total of 12v and 450 Ah at the 20 hour discharge rate.

Upon inspection, we found that the Wire from the solar panels is showing signs of damage and the connections that join the panels in parallel are not up to my spec (they seem to be covered in electrical tape and liquid tape, yuk) also the wire passses through the top of the port side combing through a drilled hole which has been covered with a huge goop of silicone sealant. 

The MPPT controller does not have any management utility, there is an upgraded version that does, but it would be cheaper to replace the unit.

I have decided to replace the wiring, I’ll use individual 10AWG wires and MC4 connectors along with a suitable cable gland where the power line passes through the fiberglass of the boat. I’ll also change the MPPT controller for one that has a remote management facility (most likely bluetooth) in order to correctly tune the charger to the system, which will include a temperature sensor on the battery bank.

Now to decide on the controller and the wiring cables, connectors and the cable clam to provide a waterproof pass through.

• 30' of 10 AWG Black Multi Strand Tinned Copper Wire
• 30' of 10 AWG Red Multi Strand Tinned Copper Wire
• 6 MC4 Connectors Male/Female Pairs
• 1 of 1M-3F Branch Connector 
• 1 of 1F-3M Branch Connector 
• Twin Cable Clam
• Victron SmartSolar MPPT 75/15 Solar Charge Controller 75V 15A with Bluetooth

 Found all of those on Amazon. I don't have a crimp tool for the MC4 connectors, hence choosing a kit that includes the crimper and wrenches. Here's a link to the shared ideas list on Amazon 

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We went down to the boat today to further inspect the wiring. The Wire, Terminals and Crimp kit as well as the twin cable clam had all arrived, time to get dirty.

Step one was to remove the Bimini canvas so that we could get to the underside of the panels. The two 65w panels have terminal boxes affixed to their undersides, with the covers off I could see the connections and the diodes, that's a good start, but the larger panel wire is connected to the Stbd side aft panel (65w) via a hole in the terminal box and a large goop of silicone. Grrrr.

So, we tested the panels.

• Port Side 65w BP Solar panel - 17.9 volts 3amps
• Stbd Side 65w BP Solar panel - 17.9 volts 3amps

• Foward 100w Solar Panel - 0.00volts 0.0amps
• Inspecting the panel, it has no terminal block and I cannot see where any diodes could be fitted! The wiring looks awful and it's connected from the Port Aft corner of the panel to the terminal box  on the Stbd panel. I checked at the inter panel connections that are on this panel and they were all zeros! This panel it no use!
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My conclusion is that the 100w panel is beyond my repair and is probably 13 years old.

Time to look for a new panel. I searched for a panel that was the same physical size 60in x 29in and could not find one, but I did find a 170w panel that uses Z brackets and they would extend the size of the panel by about 1.5" with luck it will fit, if not I'll just have to add a wider brace between the two aft panels and the new forward panel.

Here's the updated materials list

• 30' of 10 AWG Black Multistrand Tinned Copper Wire ✔
• 30' of 10 AWG Red Multistrand Tinned Copper Wire ✔
• 6 MC4 Connectors Male/Female Pairs ✔
• 1 of 1M-3F Branch Connector ✔
• 1 of 1F-3M Branch Connector ✔
• Twin Cable Clam✔
• Victron SmartSolar MPPT 100/20 Solar Charge Controller 100V 20A with Bluetooth 
• Victron Smart Battery Sense Long Range (Up to 10M)
• BougeRV 170 watts Monocrystaline Solar Panel 12volts

• BougeRV Solar Panel Mounting Z Brackets✔

Everything has either arrived or is ordered, the last item to arrive is, according to the amazon schedule, the solar panel due on September 3rd. Meanwhile I can get the other wiring taken care of. 

 

 So there's a few items to arrive, I hope to get as much as I can done before the new pan el arrives in September. I'll take more pics and post another article then. Maybe I can get Peggy to take a video showing what we are doing.

Stay tuned.