I thought I would share my knowledge of solar installations on boats with you. I hope you all find some good info here. In the last 5 years I have done 3-4 installations and gained a lot of info on what works and what does not work so well, technology has moved on at quite the pace, panels have got small, flexible and charge controllers more efficient with high outputs. PWM charging Starting with the basics. There are a few concepts of solar charging, the most common is wiring panels in parallel thus harvesting the highest output in amps and feeding this to a basic pulse width modulation charge controller. The sum of the output from the panels will be no more than the amount the batteries need to draw or has available to draw. PWM controllers also will start to restrict the amps being flowed into the batteries as the battery becomes more charged. Here are the plus and minuses of the basic method of solar charging using parallel wiring and PWM controllers. Pros – Charge controllers are cheaper! Oh that’s it really. Cons – Very thick cables required to run from solar panels to the charge controller making hard to hide (and costly). Less output Bottle neck charging as the batteries get full. One panel out of sunlight the whole array becomes inefficient. MPPT Charging Then along came MPPT charge controllers (Maximum Power Point Tracking). To save a huge lesson in electronics for those that don’t know. MPPT controllers turn unused voltage (for boats anything over 12v) into amps. They also track optimum voltage outputs. For MPPT set ups it is best to wire your panels in series (output = sum of all volts produced, amperage sum of single output of panel) But wait are we not wanting as many amps for our bucks? This is where MPPT gets clever. In an average set up with 4 100w panels on a bright day you can produce as much as 80volts DC. However your batteries only need 12v. The controller cleverly turns the residual voltage into amps! So what are the benefits? The most obvious is cable thickness from the array to the charge controller. Instead of needing to handle up to 40amps on a 4 panel set up the wiring only needs to handle 10amps (I recommend using AWG10 however as it matches the panels wire leads.) From the MPPT controller to the batteries of course you need a lot thicker wire, but this run can be very short if you place the controller near the batteries. The other benefit is less loss in shading conditions. If one panel is shaded then only the voltage drops but you would still have the other panels producing voltage to the controller to produce amperage. panel set up from design to installation. The beauty of modern panels is that they come in flexible options, some able to bend by up to 240 degrees! So boats Biminis and hard tops suddenly become a very good mounting point. How to mount. Hard top mounting is pretty straightforward. Most panels come with toggle holes in the them so you can easily bolt through. Canopy Biminis are a little more complex but with a good sewing machine or canvass shop easy to work with. To mount on the canvass, first obtain the sizes of the panel and work out how many you can get on top. Most boats will support 3-4 panels. To attach to a canvass the best option is to sew into the canvass following the inner edge of the panel industrial Velcro, sewing to the canvass the fabric portion of the Velcro strip, this is available on Amazon. I suggest at least 2” thick or wider. The toothed strip of Velcro is self sticky backed to the panel itself. When sewing in the Velcro I do suggest adding a 3” deep piece of canopy along the lead edge of the panel making a lip that flaps over the front of the panel acting as a wind shield to stop wind getting under the panel when at speed ripping the panel off. Panel wiring As written previous. If adopting the most optimum technology (MPPT charging) then the wiring should be in series, however please check with your panel supplier each panels maximum voltage handling capacity, cheaper panels do not handle more than 40v well. I opt for ones that can handle 600vDC. I recommend fitting to each positive output wire from the panel a reverse flow diode which often comes with a 10amp fuse built in. Solar panels when controllers shut off have a habit of shunting voltage back into themselves doing a fine job of self-destruction, the diodes stop this issue. Once you have all panels daisy chained in serial you will be left with of course a plus and minus lead from the panel. Using either pre made cables from Amazon or making your own (make sure 10awg) you can now feed the wire down to where you have placed the charge controller. My suggestion is as close to the battery bank as possible. Wiring to the controller is easy, the controllers are well labelled. NOTE – DO NOT plug in the positive line to the panels until you have completed all wiring! Follow controller manufacturers instruction for setting up controller! Can be a little shocking if you don’t do this! Solar has no off button other than darkness. What size controller to use? My suggestion is to ask the manufacturer or supplier. Tell them how you are wiring the panels and how many, they can determine the potential output. I always use 40amp controllers for 4 x 100 panels, however 60amp is optimum and gives lots of room for upgrading. Most good controllers will not produce more than they are rated to. Choice of storage (Batteries) My optimum choice is 4 x 6volt deep cycle batteries. When wired in series/ parallel configuration you get the best storage capacity and higher battery life. Wiring from controller to batteries. The importance here is to match controller output to wiring capability. A 40amp controller typically allows for 8AWG cable. It is imperative you put an inline fuse in between the battery and controller that matches the controller output. If the controller comes with a battery monitoring thermometer, follow instructions for installation. My choice of supplier for panels is Renogy, they are a bit more pricey but offer the best support and product reliability. For charge controllers my preferred MPPT controller is EPever. For supplies…Amazon. Good luck with your own installation and feel free to contact me if you have any questions. And on a final note, if you have any concerns doing anything yourself seek professional electricians help! Even solar can harm or worse!