Solar panel keeps blowing fuse

[RonA]

Hi All, I have a small solar panel (10W I think) to trickle charge the battery on a car that is used infrequently.
The problem I have is that when we have brilliant sunshine (not very often I know especially in the NE of UK)
is it is blowing the 0.5A inline fuse. I come back to find the battery low, not the effect I was hoping for.
Anybody else use a similar set up & similar problems, if so how have they overcome them.
Ebay have some solar charge controllers for not a lot of money would that sort the problem?
RonA

 

[Cobbler]

If the panel will produce 10 watts at 12 volts, that is just under an amp, so it doesn’t surprise me that a 0.5 amp fuse blows. Can you use a 1 amp fuse?

 

[MoreWellie]

if it really is a 10w output then that is .77 amps at 13v and .83 amps at 12v so it sounds like a .5a fuse would blow if the sun shines hard for while, you could try putting a 1amp fuse in it

is the product marked somewhere to show it should be a 0.5amp fuse? sometimes when a fuse blows people replace them with one the right physical size but not the right value depending on what is to hand

Edit: took too long typing

 

[RonA]

If the panel will produce 10 watts at 12 volts, that is just under an amp, so it doesn’t surprise me that a 0.5 amp fuse blows. Can you use a 1 amp fuse?

I replaced the 0.5A fuse because thats what it came fitted with from new (presumably to protect the solar cell). Don't really know what happens if you pull too much current from the panel.
RonA

 

[Screwdriver]

I replaced the 0.5A fuse because thats what it came fitted with from new (presumably to protect the solar cell). Don't really know what happens if you pull too much current from the panel.
RonA

My gut reaction to that observation is that the panel is trying to dump excess energy and blowing the fuse will allow it to heat up. That's just a guess so I better look it up I suppose, depends what the panel is connected to (or connected with, i.e. cheap thin wiring). Maybe the fuse is there to protect that?

 

[The_Yellow_Ardvark]

Which fuse is blowing?

The input from the panel to the regulator box?

Or the one from the box to the battery?

If the solar set up is just a panel and cables with no "box" you need to make sure the battery itself is still good.
A defective battery will try and pull more than can be supplied.

Most sets to keep a battery toped up will need to be started on a battery that is still 85% charged.

I am guessing the battery is still good?

 

[RonA]

The solar panel has no control on it, just a fuse in the wiring of the solar cell. Interesting point about the battery, I have a battery tester think I will give it a check.
RonA

 

[minimutly]

Your first two answers are correct, put a 1A fuse in. If the wiring is elcheapo chinese it might be worth stripping back the extra thick foolem insulation to check the actual conductor size, nothing surprises me anymore with their stuff. You really should have a shottky diode in the circuit as well to stop the panel from discharging the battery at night (unless it's in the panel from supplier). 1 amp is unlikely to damage anything, if you ever get to 1 amp of course as @MoreWellie says.

 

[RonA]

Just noticed something slightly odd about the solar panel.
It was supplied with a pair of crocodile clips & a plug to go in the cars cigarette lighter socket, they can be interchanged via a polarised inline connector.
The cigarette lighter socket on my car is only powered up with the ignition on, so I had to use the crocodile clips directly to the battery.
Curiously the crocodile clips are the only leads with a fuse & indeed I have an identical panel charging my caravan battery but the difference is it is charging via a cigarette socket which is always powered up. I have never had problems with the caravan solar panel.
Makes you wonder if the fuse is really necessary.
RonA

 

[Dee J]

The fuse isn't to protect the solar panel. Solar panels can drive direct into a short circuit with no damage. The fuse is far more likely to protect against fault current from the battery if there is a wiring or panel fault. The socket in the car is already fused, so that doesn't need additional fusing. So swapping to a 1A fuse should be fine. Doubt you'd need a charge controller either with such a small panel in our climate.

 

[Screwdriver]

...so I had to use the crocodile clips directly to the battery.

Well if you're going to do that, any wires coming off the battery need to be fused. Anything up to say 5 amps will be ok bearing in mind the wire itself will act as a fuse if connected directly.

 

[jimbo84]

The fuse isn't to protect the solar panel. Solar panels can drive direct into a short circuit with no damage. The fuse is far more likely to protect against fault current from the battery if there is a wiring or panel fault. The socket in the car is already fused, so that doesn't need additional fusing. So swapping to a 1A fuse should be fine. Doubt you'd need a charge controller either with such a small panel in our climate.

Spoke to technical at a solar panel company for some large ones going on a motorhome roof as it didn't mention a fuse at the panel end. The guy said pretty much the same, just put one at the battery/controller end as a short from the panel wasn't an issue.

 

[RonA]

Thanks for all the replies. I have ordered some 1A 20mm fuses, hopefully that should resolve the problems
RonA