Solar Painels

[lampshuk]

Wanting to keep Drifter's batteries topped up over winter I bought a couple of cheap, portable, solar panels last November. I think they are something like 6W max output, so not too bad for £15 each, or something. Nice and compact, they fold up like a little briefcase to stow, so easy to store and keep safe.

I asked if they were "waterproof" and was told that they should be showerproof. Since they will only be sitting in the cockpit in harbour I assumed that would be OK. After all, the worst that could happen is that they just leak a bit and get spoiled. So cheap that it's not a big deal.

Everything has been fine: batteries kept healthy etc, until this weekend when I found one of them lying face down, with the connector melted and the wires desoldered from the plug that connects them in to the front of the panel. (see photos for the front panel and the remains of the connector).

Assuming that the plastic was not melted by Southampton's intense February sun, I assume that rainwater getting in to the unit (I dismantled it and it was quite wet inside) must have created a short, so the battery discharged through the connector, melting the connector and solder so that luckily the wire disconnected before draining the battery or starting a fire. I dismantled the other one and it, too, is quite damp inside.

I was slightly surprised that rainwater was sufficiently conductive to get 12V flowing at high enough current to do this. I suppose it's possible that the wind blew the panel around and stressed the connector in such a way that there was a mechanical short.

Anyway, I thought I would post this as a cautionary tale. I plan to rebuild both panels with a more robust connector and properly waterproofed. Assuming the regulator isn't blown, of course
se.

 

[neilf39]

Surprised the regulator allowed it, you did have one between the battery and panel i presume? I would have thought that would have protected against a short on the panel side. Put a low value fuse in the wiring as close to the battery +ve as possible to protect against this.

 

[VicS]

Cannot comment on what you bought but many of these cheap solar panels are not fully weatherproof. They are suitable for use on top of a car dashboard.

When you rebiuld the system be sure to connect ir to the battery via a fuse. You are lucky this time. Without a fuse a short circuit could start a fire!

 

[Sandyman]

Was there no diode in the cct ?

 

[VicS]

Further to my earlier quick post ( I was cooking lunch at the time!):


Panels as small as 6 watts do not need regulators if the battery capacity is more than around 60 Ah.

The fuse both neif39 and I referred to should be sized to protect the wiring from the potentially high currents that the battery can supply in the event of a short circuit
It should be rated less than the safe working current of the wiring

In response to Sandyman; panels supplied for battery charging do usually have a diode fitted. An integral diode would not have prevented the damage the Ops set up has sustained.

 

[Richard10002]

A solar panel that isn't 100% waterproof isn't much use on a boat, or a house. It's only suitable for sitting inside a window, in the hope of a bit of a trickle charge - which might be fine.

 

[ghostlymoron]

Panels as small as 6 watts do not need regulators if the battery capacity is more than around 60 Ah.

Although it's not necessary to fit a regulator, I would always do so as you then get indication when the panel is charging and the state of charge of the battery which I find reassuring.

I would advise the OP to get a proper waterproof panel rather than bodge the ones he's got.

 

[Sandyman]

Further to my earlier quick post ( I was cooking lunch at the time!):


Panels as small as 6 watts do not need regulators if the battery capacity is more than around 60 Ah.

The fuse both neif39 and I referred to should be sized to protect the wiring from the potentially high currents that the battery can supply in the event of a short circuit
It should be rated less than the safe working current of the wiring

In response to Sandyman; panels supplied for battery charging do usually have a diode fitted. An integral diode would not have prevented the damage the Ops set up has sustained.

Point taken but I was referring (intended to ) to a diode in the regulator or in the wiring connections at the battery.

 

[lampshuk]

Yes, good points. I will definitely fit the inline fuse at the battery end. These panels are just intended to keep the batteries trickling away while on the berth. We have little electrical equipment on board, so I am not planning a more sophisticated setup just yet.

I have used similar cheapo units before (hung on the outside of a building) to good effect, just hadn't anticipated this failure mode.
There is a small diode and charging LED built in to the panel, but the short was "downstream" from it and it had no chance of protecting the cable.

 

[Fantasie 19]

Yes, good points. I will definitely fit the inline fuse at the battery end. These panels are just intended to keep the batteries trickling away while on the berth. We have little electrical equipment on board, so I am not planning a more sophisticated setup just yet.

I have used similar cheapo units before (hung on the outside of a building) to good effect, just hadn't anticipated this failure mode.
There is a small diode and charging LED built in to the panel, but the short was "downstream" from it and it had no chance of protecting the cable.

I had a couple of them and always found them very useful to keep my battery charged for the entire season (low power needs!) but I always mounted them one on each side inside the cabin windows.. ok, so the charge is not going to be as great, but it would avoid your problem....

 

[dslittle]

Hmmm. I am not sure what the rainfall has been like in Southampton recently but where we are, there is a bloke with a beard on the cliff knocking up a ship like structure. Might have some bearing on the 'weatherproof' panel!!!

 

[William_H]

Just guessing but I would imagine it was the wind tumbling the panel over that twisted the wire and broke it creating a short circuit at the cable entry. I doubt that rain water even with salt from off the boat surfaces could create a low enough resistance path to melt wires and terminals. So yes a fuse is necessary. The alternative is to remove the diode from the panel and locate it right at the battery terminal end of the feed wire. This should stop any current flowing from the battery ion case of cable short.
Water ingrees can cause a kind of corrosion of the elements and can be seen through the glass and is then not repairable. good luck olewill

 

[charles_reed]

Hmmm. I am not sure what the rainfall has been like in Southampton recently but where we are, there is a bloke with a beard on the cliff knocking up a ship like structure. Might have some bearing on the 'weatherproof' panel!!!

Does he have 3 sons?
Opera by Benjamin Britten?