Solar panel reading 18 volts

[Roverlord off road spares]

I purchased a boat and it came with a single solar panel on the inside of the windscreen. The blue LED is always on I know very little about these about these things, but put a multi meter on wires and it read 18Volts.
I realise these are not like an alternator , as an Alternator putting out 18 volts would cook a battery. Shouldn't a solar panel put out about 12 volts?
thanks Mario

[London Boy]

Does it have a regulator, or is that the voltage straight off the panel?

[towe0609]

That's normal, and the reason a regulator between the panel and battery is important.

[inside]

Depends which controller you are using. A cheapy will just discard the extra volts and ensure your battery is not getting too much voltage. A MPPT will convert the extra volts into amps.

My setup runs about 33 volts, this is desirable as it means long cable runs aren't too much of an issue.

So yeah regardless your controller will be taking care of things, that is if you're using one which you absolutely must on all setups.

[mike123]

The solar panel is 12volts but can reach 18volts - nothing unusual there. There should be a regulator between the panel and the battery to bring the voltage down to 12volts.

Some regulators will have a diode to stop the battery discharging at night through the panel and there may also be a diode at the back of the solar panel (in the box where the wires connect) to do the same thing.

Having a working regulator is key. Do you know how many watts the solar panel is. That will help size the regulator is you require one?

Mike

[Roverlord off road spares]

Thanks guys as I said I'm not savvy with these things, but there is no regulator that I can see. the solar panel is bolted down and has a lead from it , the lead has a cigarette lighter plug on the end of it. This is plugged into a cigarette lighter socket on the dash.
This socket is wired into the wiring on the buzz bar.
So I assume his idea was to feed the socket with the charge and it would run down along the wiring as long as the battery isolater was in the on position.
So it looks like I might need to call into Jaycar and see if I can buy a regulator for the system.

[Tank]

Thanks guys as I said I'm not savvy with these things, but there is no regulator that I can see. the solar panel is bolted down and has a lead from it , the lead has a cigarette lighter plug on the end of it. This is plugged into a cigarette lighter socket on the dash.
This socket is wired into the wiring on the buzz bar.
So I assume his idea was to feed the socket with the charge and it would run down along the wiring as long as the battery isolater was in the on position.
So it looks like I might need to call into Jaycar and see if I can buy a regulator for the system.

Solar regulator might be positioned near the battery, as it should be, Regards Frank.

[slug_burner]

Sounds like open circuit voltage is what you are reading. As soon as you connect your battery the current will start to flow and the volts will drop to the battery voltage, a little higher.

Unless the panel can put out more than a trickle charge you can get by without a regulator. The regulator saves you having to worry about forgetting to disconnect the system once the sun goes down (discharge) and the possibility of overcharging your battery due to a lengthy charge of a couple of days/weeks.

[JDNSW]

If it is only a very small panel it may not have a regulator. This is a fairly crude but common setup where the average panel output is only about the same as the self-discharge current of the battery.

If the voltage at the battery rises to 18 the battery is either dead or soon will be, but if you are measuring the open circuit voltage of the panel, that is normal.

John

[roverrescue]

JD is on the money - the fact it is behind the windscreen and plugged into the lighter socket.
My guess is it is a small panel 5W - 10W
running without a regulator to just ensure battery is always topped up.
A regulator will achieve very little in these circumstances unless you intend increasing panel size.

S