Solar panel. What do I need?

[Highndry]

Not quite your usual solar panel question, a bit more involved I think.

I have installed a deck plug for my electric outboard. It connects via a 50A breaker direct to the battery.

What do I need to install in order to be able to plug a small solar panel into the same deck plug when the outboard isn't being used?

 

[deuc02]

Some sun

 

[Croak]

If you have a solar panel surely it would be easier to have it plugged in all the time!

 

[xeitosaphil]

Problem is using a small solar panel i.e. 5w or the like, is the amount of charge you would receive (somewhere in the region of 0.4A or less) at peak sun times, is so small that it really needs to fitted permanently to gain any sort of benefit, if any at all. I assume you have a relatively large battery AH to cope with your electric outboard consumptions so the amount of charge from a small solar panel only connected occasionally will probably not be worthwhile?
You don’t actually say what size panel you are thinking of using, or size of battery bank. If battery bank is large enough, the panel may not even keep up with the batteries self discharge rate?

 

[Rigger Mortice]

I take it that you intend to unplug the engine and simply plug in the panel? Surely all you would need is a second plug to fit to the solar panel?

So long as the circuit breaker is not polarity sensitive it would work but, personally, I would not want to do that. A fault could still start a fire at 49amps when you are not on board. The solar panel circuit really needs protection from a fuse/circuit breaker which is more appropriate for the current which is likely to be drawn. For that reason I would use a separate plug. Croaks comment above would also be catered for.

 

[VicS]

Not quite your usual solar panel question, a bit more involved I think.

I have installed a deck plug for my electric outboard. It connects via a 50A breaker direct to the battery.

What do I need to install in order to be able to plug a small solar panel into the same deck plug when the outboard isn't being used?

The obvious answer is a plug to fit the deck socket.

BUT you have quite a high rated breaker (and hopefully cabling rated at least as much) presumably because this is an electric start outboard. The 50 amp circuit breaker will not offer adequate protection to the light wiring associated with a small solar panel.

My preference would be to permanently mount the solar panel and connect it directly to the battery via a suitable lower rated fuse. Failing that perhaps a socket specially for the solar panel connected to the wiring for the engine deck socket with a suitable ( in line ?) fuse incorporated into the connection.


A fused plug to fit the socket would be an good solution. Dunno if you can get fused plugs to fit deck sockets .... never seen them!

 

[Highndry]

I was thinking along the lines of fitting a matching plug to a solar panel, the idea of fitting a waterproof fuse between panel and plug appeals. Would I need to fit anything between socket and battery to prevent discharge?

BTW, it's a 20' that spends all week sitting on a trailer and the battery is used for perhaps 15 minutes (just for manouvering from the pontoon after launching) each time the boat goes out. I'm thinking a small panel would save me dragging the battery home each week to stick it on a charger.

 

[ghostlymoron]

Agree with others comments that you'd be better with a permanently connected panel through a charge regulator. I had a 10w panel on my 17' trailer sailer which lived on a swinging mooring all summer which kept the 65ahr battery fully charged all the time and meant I never had to lug the battery home for charging. I didn't have an electric outboard though but I had radio, gps and nav lights. People will tell you that you don't need a regulator and that is probably true but for a tenner I think its worth having. If the sun shines strongly (doesn't seem likely at the moment) and you're away from the boat for a few weeks, you could boil your battery.

 

[VicS]

I was thinking along the lines of fitting a matching plug to a solar panel, the idea of fitting a waterproof fuse between panel and plug appeals. Would I need to fit anything between socket and battery to prevent discharge?

BTW, it's a 20' that spends all week sitting on a trailer and the battery is used for perhaps 15 minutes (just for manouvering from the pontoon after launching) each time the boat goes out. I'm thinking a small panel would save me dragging the battery home each week to stick it on a charger.

If you buy a panel that is sold specifically for battery charging it will probably have a diode built in to it to prevent reverse current flow at night but check the technical details of what you buy.

Having said that there was a discussion on here a few weeks back about the possibility that the losses due to the volts drop across a diode when charging could be graeter than the losses due to a small reverse current when not.

Regarding a regulator. The rule of thumb is that a regulator is required if the solar panel exceeds 1 watt per 10Ah of battery capacity or if the panel is greater than 10watts.
A "pulse width modulation" (PWM) type of regulator should be the type to fit if you do need/fit one. If you fit a regulator no additional diode will be needed if the panel does not have one built in.


Penny has just dropped. When you said " electric outboard" you meant "electric outboard". Not an electric start outboard

Do the arithmetic to ensure that you have a solar panel large enough to recharge the battery fully before next using it.

 

[Highndry]

Yes, AKA trolling motor. 56lb thrust as petrol outboards are not permitted on private craft on Rutland Water.