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Solar Panels

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bjoye
Navigator

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USA
105 Posts

Initially Posted - 07/29/2022 : 08:57:26

A major component of my electrical system are solar panels. Between vhf radio, chart plotter, MFDs, refrigeration, auto-tiller, and heat, I draw a lot of power. And space is limited. I went with 2 panels, a flexible Sun Pro 50W panel on the cabin top hatch and a flexible Sun Pro 110W panel on the Bimini, each with its own controller.

The 50W panel is attached directly to the hatch via SailRite Loxx Pull It Up Fasteners.

I have enough 'play' in the 10AWG wiring to allow the hatch to slide and the pop-up to be deployed. I will need to monitor the cable for flex fatigue as it sees a lot of movement.

The 110W panel is attached to the top of the Bimini via SailRite Loxx Pull It Up Fasteners also. There is a 4mm sheet of polycarbonate panel as a backing. (flexible panels need a hard surface to be mounted to, if they flex too much it will crack the cells). The polycarbonate panel also provides air circulation underneath the panel to keep it cool.

Each controller is a Victron Blue Tooth enabled MPPT. 10AWG Marine grade wire from the M4 connectors to the controllers. (I've since added cutout switched between the panel and the controller.) Cabin top penetrations use BlueSea Cable Clams. I use one clam per conductor wire as it was impossible to obtain round insulation, 2 conductor, 10AWG marine wire at the time. (only flat was available and you can't get a good seal with the cable clam with flat insulation wiring).

6 Important notes: 1. Since each panel is of a different size in different locations ( i.e. different shading patterns), each panel gets its own MPPT controller. If you combine different size panels on one controller (series or parallel), your over all output is the smaller of the two, if series, current, parallel, voltage, hence you just turned your 110W panel into a 50W panel. 2. The easiest way to destroy a flexible panel is to bend it. It cracks the cells and creates 'hot' spots, where it melt and burn if bad enough. So a hard backing surface is a must. 3. Heat is also a killer of solar panels. There needs to be ventilation under the panel, or the panel will over heat and lead to failure. 4. Each has a cutout switch between the panel and controller. (not shown in pics). This is to protect for sudden surges when connecting or disconnecting a panel in bright sun light. (you could also throw a blanket over the panel, but in windy conditions, this can be an issue.) 5. You can walk on the panels in a limited manner, but only if you have a strong backing. I try not to walk on the the hatch panel if I can help it, and when I do, I'm very careful to apply pressure over a wide area. 6. Not all M4 connectors are compatible. They all use different tools to disconnect/connect. I'm using only Victron M4 connectors as they appear to have a better build quality than cheap Chinese connectors off of Amazon.

Over all performance has been what was expected. On good summer days, I'm seeing +400W hours on average. In winter, I only use the 50W panel, to keep the AGMs topped off and it provides more than enough power to keep my boat security systems active year round.

"Frayed Knot" 1989 C-25 WK/SR #5878

Edited by - bjoye on 07/29/2022 08:59:23

Voyager
Master Marine Consultant

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USA
5320 Posts

Response Posted - 07/30/2022 : 18:11:00

This sounds like a very well-thought-out system. Seems that you have a great deal of power you can use in your power budget. You mentioned that you have AGM batteries. How many do you have, and what�s the AH rating for each one? 80AH, 100AH? For example with two batteries, you�d have at least 160AH, if you could fully discharge the batteries.
You also mentioned that you have 400+ WH. Divided by 18VDC (Voc), that�s about 22AH.
With your fridge, auto pilot and other high power loads, what does you actual AH power budget look like?

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Edited by - Voyager on 07/30/2022 18:11:56

bjoye
Navigator

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USA
105 Posts

Response Posted - 07/31/2022 : 09:28:31

I'm actually expecting around 720 Watts per day on average during peak summer (size of panels 110+50, x 6 hours day average x .75 efficiency). Currently, I'm seeing a guaranteed minimum of 400 Watts per day. I have 2 Trojan 102Ah group 31 batteries. So at least ~120Ah to ~160Ah usable. (In general, you can take an AGM down to 40% SOC before affecting number of life time cycles, but you can go deeper down to 20% if needed, on rare occations) This year, I've only been day sailing, no overnight trips. So my batteries are always topped off. After a few hours of sailing with VHF, auto-tiller, refrigerator, chart plotter, MDFs, fans, etc... I barely put a dent into the SOC and the next day, it is all topped off again.

Cruising/multi night trips are another issue all together. Here is my power budget for Cruising / overnight trips. I've divided it into 2 sections, full day cruising, full day rest (but aboard). All of these numbers are best guess estimates, no real data yet.

As you can see, the biggest draw are the fridge, microwave and computer. At best I think I can meet my daily needs aboard on good sunny days. But on cruising or cloudy days, I'm running a big deficit. Bottom line, I'll never have enough power for continuous activity and will need to plug in every few days.