rasputin Posted August 19, 2018 Report Share Posted August 19, 2018 I have a 250w solar panel, a 20A mppt controller, 6 44ah wheelchair batteries 10 M60P NiCd batteries a 86Lb 24v electric motor, a 12v 54Lb thrust electric motor and a 2Kw generator and battery charger just in case, I have a week and a 18 1/2 foot boat to play with and try to prove my maths wrong. Link to comment Share on other sites More sharing options...
TheBiscuits Posted August 19, 2018 Report Share Posted August 19, 2018 3 minutes ago, rasputin said: I have a 250w solar panel, a 20A mppt controller, 6 44ah wheelchair batteries 10 M60P NiCd batteries a 86Lb 24v electric motor, a 12v 54Lb thrust electric motor and a 2Kw generator and battery charger just in case, I have a week and a 18 1/2 foot boat to play with and try to prove my maths wrong. It's not your maths, it's your geography. Solar boating in the UK is not going to fly on one 250W panel. @peterboat is going to be trying it with several kW and is not expecting to move very far doing it. Electric boating using a generator to charge is daft - you lose so much energy between genny -> battery charger -> battery -> electric motor -> prop that you might as well just run the outboard motor and travel twice as far for the same juice. 2 Link to comment Share on other sites More sharing options...
rasputin Posted August 19, 2018 Author Report Share Posted August 19, 2018 fly? have you missed the summer? I get 2mph out of my 35 Lb thrust, I recon that takes 500W Link to comment Share on other sites More sharing options...
MtB Posted August 19, 2018 Report Share Posted August 19, 2018 20 minutes ago, rasputin said: I have a 250w solar panel, a 20A mppt controller, 6 44ah wheelchair batteries 10 M60P NiCd batteries a 86Lb 24v electric motor, a 12v 54Lb thrust electric motor and a 2Kw generator and battery charger just in case, I have a week and a 18 1/2 foot boat to play with and try to prove my maths wrong. You haven't given any maths for us to check for you. Link to comment Share on other sites More sharing options...
rasputin Posted August 19, 2018 Author Report Share Posted August 19, 2018 Foggy maths, all the figures are there if you want to have a play with them Link to comment Share on other sites More sharing options...
rasputin Posted August 19, 2018 Author Report Share Posted August 19, 2018 solar panel will give me 120A for 8 hours gives me a kW I recon a kW will give me 4 miles Link to comment Share on other sites More sharing options...
TheBiscuits Posted August 19, 2018 Report Share Posted August 19, 2018 1 minute ago, rasputin said: solar panel will give me 120A for 8 hours gives me a kW I recon a kW will give me 4 miles Eh? Your solar panel will give you 20A maximum under perfect laboratory conditions using a 20A controller. Flat mounted in the UK you will be lucky to get 10A out of it, and that assumes you don't ever cruise in the shade - trees, bridges, tunnels, clouds etc. I would expect that your 35lb trolling motor will draw something like 30-40A at 12V - are you measuring the current to the motors? @peterboat has bought 14 Lithium batteries at 138Ah each to try and run his motor. I think you are going to kill your wheelchair batteries very quickly indeed if you don't measure how much you are taking out of them. Link to comment Share on other sites More sharing options...
rasputin Posted August 19, 2018 Author Report Share Posted August 19, 2018 (edited) 10A x 12v x 8 hours gives 960W ? sorry wrong letter. so, my 54lb will draw 80A at 12v, 1 hour a day at 4mph I want to do 24 miles in the week so 6 days charging? Edited August 19, 2018 by rasputin Link to comment Share on other sites More sharing options...
TheBiscuits Posted August 20, 2018 Report Share Posted August 20, 2018 3 minutes ago, rasputin said: 10A x 12v x 8 hours gives 120W ? sorry wrong letter Quite an important one when discussing electrics - bad combinations of A V W h get the engineers all upset. So your thinking is similar to mine - you will be able on a clear sunny day with no shade to provide under a quarter of the power your 35lb trolling motor uses in an hour. How do you recharge the batteries after that? Link to comment Share on other sites More sharing options...
rasputin Posted August 20, 2018 Author Report Share Posted August 20, 2018 (edited) Quarter? solar will give me about 1kw per day 35lb engine will use about 1kw per day run for 2 hours where am I going wrong? yes I am aware I will upset the engineers, trying hard not to, Edited August 20, 2018 by rasputin Link to comment Share on other sites More sharing options...
MtB Posted August 20, 2018 Report Share Posted August 20, 2018 Amps x Volts = Watts. Watts x hours = WattHours. Slotting in your numbers, 10A x 12V = 120W. 120W x 8 hours = 960WattHours You motor drawing 80A at 12V is drawing 80A x 12V = 960Watts. (Coincidence or what?!) So the 8 hours of charging from your panel will theoretically generate enough energy to run the motor for one hour. However this assumes no charging losses and 10A exactly for the full 8 hours, neither of which happens in real life. Charging losses will perhaps be 10% and that 10A charging current will probably be closer to 3A at each end of the 8 hour period, judging by the performance of my own solar installation, so my guess is about two days of charging will run your motor for one hour, based on your figures. 2 Link to comment Share on other sites More sharing options...
Alan de Enfield Posted August 20, 2018 Report Share Posted August 20, 2018 6 hours ago, Mike the Boilerman said: around However this assumes no charging losses and 10A exactly for the full 8 hours, neither of which happens in real life. Charging losses will perhaps be 10% and that 10A charging current will probably be closer to 3A at each end of the 8 hour period, judging by the performance of my own solar installation, so my guess is about two days of charging will run your motor for one hour, based on your figures. As we (all) know, the actual output gained at latitude 53 degrees, and taking into account the odd cloud, tree cover, tunnels, rainy days, shorter days in the Spring and Autumn, lower angles of incidence of sunlight in the Spring & Autumn all mean that it is nearer 50% of the theoretical output. Output in October to March may TOTAL 1 hours motor running Link to comment Share on other sites More sharing options...
Murflynn Posted August 20, 2018 Report Share Posted August 20, 2018 bitter experience: I have been cruising with my small yogurt pot for 4 years now, only during the height of summer when sunny weather is predicted. I have 600W solar installed (and 660AH batteries). On a good sunny day I expect to generate about 2kWh. My 12v motor draws about 40A including losses in the cables and controls, so it will run for 4 hours before depleting the batteries. GPS speed indication is average 3mph. In practice I cruise about 10 hours a day (say 8 hours running and 2 hours locking) and I need to get a hook-up every night to recharge. To improve the situation I am currently building a longer, sleeker, lighter boat designed specifically to run faster and further using a trolling motor. Construction - tortured plywood (conical sections with enormous structural strength) stitch and glue, with GRP sheathing. However, I will still need to recharge overnight. Solar is fun to play with but unlikely to ever be a serious source of motive power in northern Europe. 2 Link to comment Share on other sites More sharing options...
rasputin Posted August 20, 2018 Author Report Share Posted August 20, 2018 Thanks, nice to hear some real life figures. How big is your boat? Link to comment Share on other sites More sharing options...
peterboat Posted August 20, 2018 Report Share Posted August 20, 2018 My first electric boat was a 32 x 12 broads cruiser, it has a 24 volt Cedric Lynch motor at 3mph it draws 23 amps at 24 volts. Ii also has a large roof so can accommodate a lot of solar, it also has a 24 volt whispergen for lecce and heat The boat I am converting is 57 x 12 will have 3kw of solar a series motor running at 60 volts, it also has a 24 volt domestic bank on solar and a 24 volt whispergen, I expect in summer to move for a couple of hours a day on solar which is ok for me Link to comment Share on other sites More sharing options...
Alan de Enfield Posted August 20, 2018 Report Share Posted August 20, 2018 1 minute ago, peterboat said: 3kw of solar a series motor running at 60 volts, it also has a 24 volt domestic bank on solar and a 24 volt whispergen, I expect in summer to move for a couple of hours a day on solar which is ok for me If the OPs equipment is similarly rated then you would expect his 250w solar system to support about 10 minutes cruising. Link to comment Share on other sites More sharing options...
MtB Posted August 20, 2018 Report Share Posted August 20, 2018 An oversight in my brief calcs above is your 80A motor will probably not need to draw 80A during normal cruising. Only for stopping and starting. More likely 40A at 3mph steady speed. So so you may well get closer to one hour of cruising from one day of charging. Link to comment Share on other sites More sharing options...
peterboat Posted August 20, 2018 Report Share Posted August 20, 2018 Its difficult for me to judge as the broads cruiser is so economical on power [it has a proper underwater shape] next year will tell me if I have got it right or wrong, however others have done this before with success so who knows 1 minute ago, Mike the Boilerman said: An oversight in my brief calcs above is your 80A motor will probably not need to draw 80A during normal cruising. Only for stopping and starting. More likely 40A at 3mph steady speed. So so you may well get closer to one hour of cruising from one day of charging. If it has a boaty shape and is light it will draw less, it will be better than my Broads cruiser I should think Link to comment Share on other sites More sharing options...
WotEver Posted August 20, 2018 Report Share Posted August 20, 2018 9 minutes ago, Mike the Boilerman said: ... you may well get closer to one hour of cruising from one day of charging. ... in the summer. Link to comment Share on other sites More sharing options...
Boater Sam Posted August 20, 2018 Report Share Posted August 20, 2018 Its probably more efficient to use the solar power to grow sugar cane, eat the cane and use the energy to pull the boat on a rope. I think you may go further that way and get fit. Of course its still seasonal. Link to comment Share on other sites More sharing options...
peterboat Posted August 20, 2018 Report Share Posted August 20, 2018 9 minutes ago, Boater Sam said: Its probably more efficient to use the solar power to grow sugar cane, eat the cane and use the energy to pull the boat on a rope. I think you may go further that way and get fit. Of course its still seasonal. Solar works and as long as you arnt in a hurry its very cheap and clean Link to comment Share on other sites More sharing options...
rasputin Posted August 20, 2018 Author Report Share Posted August 20, 2018 23 minutes ago, Boater Sam said: Its probably more efficient to use the solar power to grow sugar cane, eat the cane and use the energy to pull the boat on a rope. I think you may go further that way and get fit. Of course its still seasonal. Pulling the boat is an expected option and I have packed a harness for that eventuality Link to comment Share on other sites More sharing options...
Jen-in-Wellies Posted August 20, 2018 Report Share Posted August 20, 2018 Does sound like solar-electric boating is only going to be practical if you are on the Suez Canal, rather than the UK. I do like the idea of silent boating though. Horses are expensive to run and people bow hauling aren't silent as they whinge a lot! Jen 1 Link to comment Share on other sites More sharing options...
RLWP Posted August 20, 2018 Report Share Posted August 20, 2018 2 minutes ago, Jen-in-Wellies said: people bow hauling aren't silent as they whinge a lot! Jen Not if they are doing it right - no breath for moaning 1 Link to comment Share on other sites More sharing options...
TheBiscuits Posted August 20, 2018 Report Share Posted August 20, 2018 26 minutes ago, Jen-in-Wellies said: Does sound like solar-electric boating is only going to be practical if you are on the Suez Canal, rather than the UK. I do like the idea of silent boating though. It can work if you only expect a few hours moving a week and have a decent solar array and a large battery bank. Sadly, @rasputin doesn't, and with 250W of solar on an 18ft boat I suspect he has run out of roof room to install more. I am actually more concerned about his batteries, as they seem quite small capacity for doing this. The rough rule of thumb for trolling motors is that a fully charged 110Ah battery will give about an hour of propulsion. He has some 44Ah batteries, presumably secondhand, and I doubt they will be able to store enough sunlight to run the motor for a couple of hours. Link to comment Share on other sites More sharing options...
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