24v solar panel charger

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HunterWanderer

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Ive got a 100lb 24V electric outboard on my 1948 27' 3 ton broads sailing cruiser which pushes it along at about 3.5 kts for about 5 hours which Im happy with.
I charge the batteries from the mains but would like to change it to use a solar panel to recharge the batteries between trips (usually only on sundays). Ive got deck space for a semi flexible 100w panel but would this charge the 24v batteries properly?
The idea of a solar powered boat does appeal.
 
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HunterWanderer said:
Ive got a 100lb 24V electric outboard on my 1948 27' 3 ton broads sailing cruiser which pushes it along at about 3.5 kts for about 5 hours which Im happy with.
I charge the batteries from the mains but would like to add a solar panel to recharge the batteries between trips. Ive got deck space for a semi flexible 100w panel but would this charge the 24v batteries properly?
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It would provide a useful amount of energy, would charge the batteries between trips, depending upon how long between trips and how much the Sun shines. Well worth fitting.
 
You might need to have two panels connected in series to charge a 24 volt system. They could be two 50 W if that's all the space you have. I don't use my boat batteries for propulsion, but a 30 W panel keeps them fully charged all year.
 
neil_s said:
You might need to have two panels connected in series to charge a 24 volt system. They could be two 50 W if that's all the space you have. I don't use my boat batteries for propulsion, but a 30 W panel keeps them fully charged all year.
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Good point, i'd not allowed for the 24v, he will need to fit 2x50w and connect in series.
 
^^^ what PR says about the controller

But you don't tell us the capacity ( Ah) of your batteries or give any indication of the power of your outboard or its normal cruising current draw ( amps). It is therefore difficult to say if your 100 watts of solar power will be sufficient to recharge the batteries between Sunday outings.
 
As said it is anyone's guess whether you could recharge your batteries before the next use. Much depends on sunshine available orientation of the panels ie tilted towards the sun and facing south. However with decent battery monitoring you may achieve solar recharge between voyages. But you would really need to know how much went in to estimate voyage time available.
Now your cheapest source of solar anel is the 200w aprox variety used for domestic PV systems. Cheap because they are used in huge quantities. Our club has 200 panels on the roof. They do provide 40volts no load so could be used with a PWM controller or MPPT. However may be just too big for your boat. You could expect 5 amps from the panel for maybe 6 hours per day in summer (at best) giving you 30 amp hours per day. If you must go smaller physical size then you would need as said 2 panels in series. Although one panel with MPPT controller might work. Not all MPPT would do it however.
Don't be tempted to buy this controller claimed to be OK for 24v battery. https://www.ebay.com/itm/30A-Solar-...977953?hash=item361d21a421:g:RbgAAOSw0bJZr-Y6 Mine dropped dead with 2x 10w panels in series fairly quickly. (charging a mobility scooter) (tractor to tow my dinghy) good luck olewill
 
A 100lb thrust electric outboard is typically about 1100W or 45A at 24V?
https://www.amazon.co.uk/N150-24V-Brushless-Electric-Trolling-Saltwater/dp/B00WF07YKM
So, say it's run at half power for 5 hours, you are looking at something like 100Ah used?
Allowing for charging inefficiency, maybe 150Ah needed to charge?
That's about 4300Wh
43 hours equivalent full sunshine for a 100W panel
By the time you allow for the panel not exactly facing the sun etc, it does not look adequate.
It is a useful contribution in good weather IMHO, but not a solution.
 
This is the motor;
https://www.ebay.co.uk/itm/BISON-10...364408&hash=item4d5ab2d26d:g:sUkAAOSw8lpZJZHt
and I have six 110ah 12 v batteries.
I use it at full speed for about 2 hours so about 3800 to 4000 Wh needed for full charge.
Topping up with the battery charger for the 24 hours before going out is an option as the boat is nearby.
Im now thinking of using 4 x 50W panels that can be folded away easily then put up and plugged in when I get back.
 
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