Solar panel for an electric o/b - or just get a second battery?

[RO'D]

Hi folks,

I'm soon to be the owner of a 14 foot sailing dinghy, which will be used for both racing and general pottering / social outings.
After years of messing around with ICE O/Bs I'm looking to start afresh with an electric O/B.
Some of the outings would probably be at the upper range of the battery - so I was considering getting a folding solar panel to top it up.
Is this a feasible proposition, or should I just get a second battery as my backup?
(Boat will be used in Ireland, not known for its day long sunshine).

Ideally the panel could also be used for general purposes e.g. also charging a cool box, phones etc
From looking at the electric O/B website their panels would seem to only be compatible for use directly to the O/B so no flexibility there?

Does anyone have any practical experience of this setup?
Thanks
RO'D

 

[Ingwe]

Hi folks,

I'm soon to be the owner of a 14 foot sailing dinghy,

Surely your going to using the sails for the majority of the time and only using the outboard in an emergency?

I currently have a First 18 which we have a Torqueedo on board to get us home if the wind dies, range would be 8-10 miles. However we have only used the Torqueedo once in the past 2 seasons, basically it is far quicker and easier to paddle out of the marina when necessary and then once out we will be using the sails.

So I would hang fire on spare batteries / solar panels until you have the boat and been out a few times to see exactly how you are going to use it.

 

[RO'D]

Yes I'll happily be sailing most of the time, and won't be bringing the O/B
The range issue is around some specific trips which will be O/B only - e.g. exploring waterways / under bridges etc.

 

[fredrussell]

I think electric OBs these days have batteries from 500 to 1000 watt/hours capacity. A 50 watt panel will (realistically) be chucking out 25 watts or so - so you can see it’ll be a fairly slow way to charge an OB battery. Personally I’d get a second Li battery and work out a way to charge OB from that. I say work out a way because OB battery voltage and Li battery voltage will be different.

 

[JerryRhum]

How would you charge the batteries without a solar panel?

I have an electric motor, but to charge the batteries I have to lift them out of the boat, carry them back to the car and charge them at home. They are heavy and it is a faff.

I do have a (small) solar panel on board and, in the summer, it will charge a leisure battery between one weekend use and the next. In the winter I don't think I have got a full charge.

I've gone for 'belts and braces' leaving one battery on board charging from solar, and two lifted out and charged at home.

 

[Sea Change]

Does the electric OB have a 12v charger option? If so you might find that you can have a setup something like: solar panel -> charge controller-> 12v battery -> charger -> OB.

In other words, you probably need the second battery anyway.

 

[Ian_Edwards]

I've had an ePropulsion Spirit plus 1.0 for 2 seasons now.
It works well. It's about the same weight as a 2.5hp 4 stroke outboard it replaced. But has the advantage of having 2 parts, battery and leg so it's easier to carry and store and no need to carry petrol.
I came with a mains charger. You can buy a 12v charger.
You can also buy a second battery, which just slots in, like the one original.
The battery is 1 kWh, so a 100 W solar panel, outputting 50 W would take about 20hr to charge it from empty to full. However, it's unwise to run the battery down to zero. I usually start recharging between 10% and 20%.
How far you can go on one charge largely depends how fast you go, and it's not a linear relationship. You'll go a lot further at 50% than at 100%.
My guess is that an ePropulsion Spirit plus 1.0, would work well for the OP, but it's a really expensive option.

 

[William_H]

It seems to me your electric o/b may have an internal Lithiou battery or use an external lead aid battery (heavy). I am guessing you would go for internal lithium battery type. In any case as said you would need a very large solar panel to do any real charging while you are away from home. A more manageable sized panel would not do any worthwhile charging over a few hours. As said get an extra battery if you need more range or carry oars. ol'will

 

[webcraft]

We run a small trolling motor

It seems to me your electric o/b may have an internal Lithiou battery or use an external lead aid battery (heavy). I am guessing you would go for internal lithium battery type. In any case as said you would need a very large solar panel to do any real charging while you are away from home. A more manageable sized panel would not do any worthwhile charging over a few hours. As said get an extra battery if you need more range or carry oars. ol'will

We charge a 60 Ah lithium battery used to run a trolling motor using a 100W folding solar panel.

Charging from 30% to 85% typically takes around 8 hours in full (Algarve) sun.

- W

 

[Boathook]

We run a small trolling motor


We charge a 60 Ah lithium battery used to run a trolling motor using a 100Ah folding solar panel.

Charging from 30% to 85% typically takes around 8 hours in full (Algarve) sun.

- W

Do you mean 100 watt solar panel. Never heard of 100Ah being used.

 

[fredrussell]

Whilst the use of trolling motors in often poo-pooed by some on here, I do feel there’s a case to be made for buying a cheap 2nd hand one and using it with a lithium battery. Often see 50 - 60 lb thrust one’s on eBay for £100 or so. At that price, if you get three or four years before the rust sets in, your still quids in compared to Torqeedo and the like.

 

[webcraft]

Do you mean 100 watt solar panel. Never heard of 100Ah being used.

Sorry, yes of course 100W panel, 60Ah battery.

- W

 

[dunedin]

Hi folks,

I'm soon to be the owner of a 14 foot sailing dinghy, which will be used for both racing and general pottering / social outings.
After years of messing around with ICE O/Bs I'm looking to start afresh with an electric O/B.
Some of the outings would probably be at the upper range of the battery - so I was considering getting a folding solar panel to top it up.
Is this a feasible proposition, or should I just get a second battery as my backup?
(Boat will be used in Ireland, not known for its day long sunshine).

Ideally the panel could also be used for general purposes e.g. also charging a cool box, phones etc
From looking at the electric O/B website their panels would seem to only be compatible for use directly to the O/B so no flexibility there?

Does anyone have any practical experience of this setup?
Thanks
RO'D

Hope you enjoy your new dinghy. Intrigued what type of dinghy it is, as few 14 foot dinghies are used these days for both racing and general pottering? Most boats used for racing these days have open sterns etc which would prevent fitting a motor, for example.

However, going back to your questions, the key thing with electric outboards / propulsion is to DO THE MATHS. Always important to do some simple calculations to check the feasibility, and they are very simple.

Clearly solar panels can’t be used for material “range extension” - ie to extend a single continuous journey. A typical £2k electric outboard will be rated at 1kW power. Even pootling at quarter throttle, that is 250W. To keep up with that might need at least 500W of solar panels in perfect sunshine, perfect alignment and zero shade. That would probably entirely cover a 14 foot boat. Slightly impractical.

The battery is typically 1kWh. Not sure what the rated output is of your intended folding solar panel? Perhaps 50W or 100W theoretical maximum? So divide by at least 2 for practical output on an ideal day. Then work out how many hours would be needed to charge from say 20% to 80% - ie needing 600Wh input.
Perhaps worthwhile if always staying at the destination for a full day or more in good sunlight before returning. But not otherwise. Taking a mains charger and going to a friendly pub might be more effective.

In practice my 2.5hp two stroke is a much more practical proposition for that type of use. And only cost £250 second hand.

 

[Sea Change]

Whilst the use of trolling motors in often poo-pooed by some on here, I do feel there’s a case to be made for buying a cheap 2nd hand one and using it with a lithium battery. Often see 50 - 60 lb thrust one’s on eBay for £100 or so. At that price, if you get three or four years before the rust sets in, your still quids in compared to Torqeedo and the like.

That's exactly what I did. £100 for a secondhand 68lb thrust Bison, plus £280 for a 60Ah lithium battery. This was back in 2021 so that was an absolute steal.
I used it quite a bit but the Bison motor eventually started falling apart. One transom clamp stripped its thread in the plastic mount. The plated mild steel bolts and springs rusted and I could no longer lift, tilt, adjust steering friction, or lock the leg up.
The motor simply connected to the battery using screw on terminals, so there was no protection from water, and I had to repeatedly cut down the cables and crimp on new eyes.
The cheap battery didn't have Bluetooth so I couldn't tell how much range I had left.
Finally, at about 4.5kt, the motor was slower than sailing and not much faster than rowing.
It was wonderfully quiet and civilised though.

I think to make a trolling motor a practical idea you need to invest a little more than I did. Webby seems to have it work well, with the battery in a waterproof box, with a Bluetooth battery monitor, and waterproof connectors. I might do the same at some point, with a lower powered motor (under 50A makes it easier to find connectors).

 

[fredrussell]

That's exactly what I did. £100 for a secondhand 68lb thrust Bison, plus £280 for a 60Ah lithium battery. This was back in 2021 so that was an absolute steal.
I used it quite a bit but the Bison motor eventually started falling apart…

Fair point(s) but I guess the point I was making was that, yes, these motors are not going to last that long before the rust kills them, but they’re very cheap compared to proper leccy ones. You could buy 20 ones like yours for the cost of a Torqeedo etc!
Just out of interest, how feasible would it be to replace the failed parts you mentioned with SS parts?

 

[Sea Change]

Fair point(s) but I guess the point I was making was that, yes, these motors are not going to last that long before the rust kills them, but they’re very cheap compared to proper leccy ones. You could buy 20 ones like yours for the cost of a Torqeedo etc!
Just out of interest, how feasible would it be to replace the failed parts you mentioned with SS parts?

I think it would be relatively straightforward. And I've learned my lesson about the transom clamps- don't overtighten! I fixed that particular problem by boring out to a larger size and then putting in a larger bolt. But it meant I had to take a spanner with me, and it was very very stiff to use. Just another reason I stopped using it.

 

[LiftyK]

Speed has a big Impact on range. Try your motor and see what you can get from it at a modest but acceptable speed.

 

[toothless]

I have been mucking about with torqeedo motors for a while now and think I can help. This website was really useful Range Extension options Torqeedo 1003 and Ultralight - The Torqeedo Shop

As per the tables nearer the bottom, any reasonably new torqeedo travel battery on their prev model outboards can accept a charge of up to 50v and 4a, though it can't really accept much over 100w at a time and will max out at that. It also can't take more than 4a at any voltage. This means you can directly attach a solar panel of circa 100w, or indeed connect to a leisure battery directly (but you will be limited to 12v*4a =48w charging. If hooking up to a leisure battery you are best off doing it via a voltage booster which are cheap on amazon so you get the full charging rate. You CAN charge while using the motor - the charge just gets deducted from the power being taken from the torqeedo battery.

In terms of range extension - totally depends on your boat but I find when shoving the club dinghy along at 2 knots I use about 150w. 4 knots nearer 600w. So at 2 knots your solar/leisure battery does most of the work, at 4 it just helps a bit.

I've now gone off the deep end and have made a custom controller so I can run my torqeedo directly from my big boats 24v lithium bank so I can unlock a bit of hybrid electric sailing which has also worked very well indeed. But that's a much bigger project!

 

[nestawayboats]

There are lots of electric outboards out there but the market leaders - if you're looking for an electric outboard with approx 1kW power and integral but removable lithium battery - are ePropulsion and Torqeedo. From those two manufacturers the choices are:
- ePropulsion Spirit PLUS 1kW motor with 1276Wh capacity battery £1875
- Torqeedo 903 (older design still available) 900W motor with 915Wh battery £1695
- Torqeedo Travel S (new 2024 design) 1100W motor with 1080Wh battery £2300

The 903 is cheapest, the ePropulsion gives you the most battery for your money, the newer Torqeedo Travel design has some very nice features and eliminates cables from the connection process (more like a battery drill).

In terms of driving a 14 foot sailing dingy along, to all intents and purposes, they'll all do the same thing at the same power output. I haven't read this thread to the last comma but don't think the dinghy type has been specified... however as a moderately well-informed guess you'll probably get about 3 knots at 250-300W, 4 knots at 400-500W, and 5 knots at 1000W.

In terms of range then, at 4 knots:
- ePropulsion Spirit should give you at least 10 nautical miles (1276/500 = 2.5, 2.5x 4 =10)
- Torqeedo 903 should give you 7-8 nautical miles
- Torqeedo Travel S should give you 8-9 nautical miles

However do not forget your range will all-but halve if you ramp it up to 5 knots. People do seem to forget in these discussions that with an electric outboard the journey itself will actually be pleasant. Electric outboards are near-silent and vibration-free (particularly compared to small single cylinder petrol outboards!), so if you take slightly longer to get there it's not necessarily a terrible thing.

Back to OP question which I'll paraphrase/clarify as "will a solar panel do anything useful in terms of range in real time?". And the answer is no, not really, for a solar panel that's realistic on a 14ft dinghy. ePropulsion offers the fastest 12V/Solar charger, now up to 400W (new 2024 model) - and as above 400W would equate to a useful amount of power/speed - but a 400W panel is huge in the context of this type of boat. If you took the rig off and put a solar roof on it, maybe. But even then and as others have pointed out that 400W still only comes on a perfectly sunny day with perfect alignment of the panel perpendicular to the sun, and no shading at all.

If you only needed slightly more than the battery capacity and your motoring voyage was fairly leisurely, over the course of a day with several stops, then a 100W panel might put back enough to extend your range by 4-5 nautical miles (on a sunny day). If you were to slow down just slightly from 4 knots, 15 nautical miles is now well in your sights, even 20nm might be possible. Quite long distances in a small open boat?

If you want more than that simplest way to add range on this sort of motor is another battery, doubles it, simple as that. Big "redundancy" advantage and if it's a two-way journey, as long as you only use say 80% of one battery in one direction, the remaining 20% of that plus 100% of the second one should usually get you back (unless you've done literally zero planning in terms of wind/tide/current!).

Cheaper and still pretty simple, if your motoring voyage involves a pub or similar (somewhere in the middle), but without the redundancy benefit, is a single battery with fast mains charger. The ePropulsion Spirit fast charger will put back about 30% per hour so assuming you haven't arrived at zero percent the duration of a decent lunch could have you back to full or near enough.

As always and in the interest of clarity I should point out we actually sell these things, so we do have some commercial interest... but do also know roughly what we're talking about (have been using and selling Torqeedos for 17 years)!

Ian
Nestaway Boats

 

[Plum]

There are lots of electric outboards out there but the market leaders - if you're looking for an electric outboard with approx 1kW power and integral but removable lithium battery - are ePropulsion and Torqeedo. From those two manufacturers the choices are:
- ePropulsion Spirit PLUS 1kW motor with 1276Wh capacity battery £1875
- Torqeedo 903 (older design still available) 900W motor with 915Wh battery £1695
- Torqeedo Travel S (new 2024 design) 1100W motor with 1080Wh battery £2300

The 903 is cheapest, the ePropulsion gives you the most battery for your money, the newer Torqeedo Travel design has some very nice features and eliminates cables from the connection process (more like a battery drill).

In terms of driving a 14 foot sailing dingy along, to all intents and purposes, they'll all do the same thing at the same power output. I haven't read this thread to the last comma but don't think the dinghy type has been specified... however as a moderately well-informed guess you'll probably get about 3 knots at 250-300W, 4 knots at 400-500W, and 5 knots at 1000W.

In terms of range then, at 4 knots:
- ePropulsion Spirit should give you at least 10 nautical miles (1276/500 = 2.5, 2.5x 4 =10)
- Torqeedo 903 should give you 7-8 nautical miles
- Torqeedo Travel S should give you 8-9 nautical miles

However do not forget your range will all-but halve if you ramp it up to 5 knots. People do seem to forget in these discussions that with an electric outboard the journey itself will actually be pleasant. Electric outboards are near-silent and vibration-free (particularly compared to small single cylinder petrol outboards!), so if you take slightly longer to get there it's not necessarily a terrible thing.

Back to OP question which I'll paraphrase/clarify as "will a solar panel do anything useful in terms of range in real time?". And the answer is no, not really, for a solar panel that's realistic on a 14ft dinghy. ePropulsion offers the fastest 12V/Solar charger, now up to 400W (new 2024 model) - and as above 400W would equate to a useful amount of power/speed - but a 400W panel is huge in the context of this type of boat. If you took the rig off and put a solar roof on it, maybe. But even then and as others have pointed out that 400W still only comes on a perfectly sunny day with perfect alignment of the panel perpendicular to the sun, and no shading at all.

If you only needed slightly more than the battery capacity and your motoring voyage was fairly leisurely, over the course of a day with several stops, then a 100W panel might put back enough to extend your range by 4-5 nautical miles (on a sunny day). If you were to slow down just slightly from 4 knots, 15 nautical miles is now well in your sights, even 20nm might be possible. Quite long distances in a small open boat?

If you want more than that simplest way to add range on this sort of motor is another battery, doubles it, simple as that. Big "redundancy" advantage and if it's a two-way journey, as long as you only use say 80% of one battery in one direction, the remaining 20% of that plus 100% of the second one should usually get you back (unless you've done literally zero planning in terms of wind/tide/current!).

Cheaper and still pretty simple, if your motoring voyage involves a pub or similar (somewhere in the middle), but without the redundancy benefit, is a single battery with fast mains charger. The ePropulsion Spirit fast charger will put back about 30% per hour so assuming you haven't arrived at zero percent the duration of a decent lunch could have you back to full or near enough.

As always and in the interest of clarity I should point out we actually sell these things, so we do have some commercial interest... but do also know roughly what we're talking about (have been using and selling Torqeedos for 17 years)!

Ian
Nestaway Boats

Really appreciate your advice.