It's important to do the math on the solar input and understand its' limitations. Start with the fact that 1 hp = 745 watts. Even if we had 100% efficiency from solar panel to prop (which we don't - figure 85% at best, less when charging battery and then drawing from battery), we would need 745 watts of solar panels at full output (full sun, optimal angle to sun, no shading of panels) to give us 1 hp equivalent. And that would only apply for 4-5 hours around mid-day. Not sure where anyone would be able to rig that much panel on a Monty...tow a barge behind? But then you've got to pull the barge too which adds to the hp needed... So it's not possible to realistically power a Monty (or any boat other than exotic experimental craft built specifically for the purpose) by electric motor direct from solar panels alone. You could move it around a bit on an ideal day but for any current, breeze, etc. forget it. That's what the batteries are for. As a practical example, I met a guy at Fern Ridge some years ago who had an S2 6.7 (drop daggerboard light displacement racing boat, ~22 ft and ~2200 lbs displacement). He was experimenting with running his Torqeedo off panels only. He put what panels he had on deck, along both rails, I think he had maybe 250-300W max, and of course they got shaded by sail and/or rigging as he maneuvered. Less than 1/2 hp, absolute best case on a clear sunny day. So he was able to motor slowly around the glassy marina, but anything much more challenging, there would not be enough power. There are electric inboard motors for cruising sailboats, they use regeneration to recharge the batteries when sailing wind is good. And they have lots of big batteries... cheers, John On 5/11/21 4:33 PM, Sailing Spark wrote:

Torqeedo and epropulsion also have solar "blankets" that you can unfurl to help charge their batteries. They can also be used to supply power while using them, depending on your speed, could theoretically extend your cruising to infinity or until the sun goes down. I will be running an Epropulsion outboard on my Monty when I get her back in the water. It's not that I have range anxiety, I have start anxiety. Provided the batteries are charged, electric motors almost always start

Art Haberland Monty#406 *Tea*

On Tue, May 11, 2021 at 1:53 PM John Schinnerer via montgomery_boats < montgomery_boats@mailman.xmission.com> wrote:

...

The weak point in all electric systems is the battery.

The reason Torqeedos (and electric bicycles) cost so much is in significant measure because of the lithium batteries.

If you want to stay with the affordable and heavy lead-acid batteries then you will spend money regularly on a new battery, but otherwise it's fairly inexpensive. You can buy 3-5+ lead-acid marine/RV batteries for the price of one (much lighter) lithium battery of similar capacity. And they are readily recycled to reclaim the lead.

Note that those marine/RV batteries will die fast if you run them down more than 20% regularly. They are not true "deep cycle" batteries, which are rated at 50% discharge cycles. "Marine/RV deep cycle" are typically only rated 20% discharge cycles. Which means, the expected life or number of cycles from the manufacturer is based on no more than 20% discharge per cycle (50% per cycle for true deep cycle batteries). If you repeatedly discharge deeper than that, their life shortens considerably.

If you are just going to/from a mooring fairly close to shore then you could be fine in terms of battery use.

Also depends on how often you use the motor, and the math of solar panels and battery capacity & charging. A panel small enough to be not in the way on a Monty is basically a trickle charger for a trolling motor size battery. It will not keep up with motor use if you use the motor more than a certain amount. The calculations of "a certain amount" can be done but there's a lot of details needed...beyond the scope of this reply :-).

If you are within the sustainable window of solar input vs. motor use a trolling motor will do ya with minimal hassle.

If you're outside that window, then you will be having to haul that heavy battery home repeatedly to charge it up (and then haul it back out to the boat and wrestle it back where it lives...). Less of an issue at a dock, more of a hassle on a mooring to transport that battery.

cheers, John

On 5/11/21 10:30 AM, Jon Barber wrote:

...

Yet another trip to the mooring where I am smelling gasoline. I love the 2 hp Honda, but i realize in many situations I really only need a small push here and there. My thought was to buy a trolling motor, extra battery and a solar panel. There us plenty of sun where I live. The Honda leaks just enough to perfume my cabin with gas fumes. I will be making the necessary repairs; fuel lines and cap, but can anyone offer their wisdom re electric options? Torqueedo is out of the question as to the price. Thanks Jon Barber Monty17l Ol'44

-- John Schinnerer - M.A., Whole Systems Design -------------------------------------------- - Eco-Living - Whole Systems Design Services People - Place - Learning - Integration john@eco-living.net - 510.982.1334 http://eco-living.net http://sociocracyconsulting.com

-- John Schinnerer - M.A., Whole Systems Design -------------------------------------------- - Eco-Living - Whole Systems Design Services People - Place - Learning - Integration john@eco-living.net - 510.982.1334 http://eco-living.net http://sociocracyconsulting.com