Suitcase solar power question

[Scouser1]

I got a 13w suitcase solar power from Makro a couple of years ago. I've never been happy with it's performance. In fact, every time I've used it, the battery loses it's charge rapidly. Yesterday, I happened to check the voltage coming out, and it was generating 24v instead of 12v. This can't be normal, surely, and will I have done my leisure battery any damage?

Norman

 

[ProfJohnL]

Hello Scouser.

The output voltage from the solar cell has to be higher than the battery terminal voltage to be able to 'push'current into the battery.

But it does depend on how you measured the voltage. I will assume that you simply put a volt meter across the cell's output, without it being connected to anything else. This is called the open terminal voltage, and I am not suprised that you found 24V.

This is quite normal.

The voltage will drop as the the cell provides current. This is unlikely to damage your battery, however larger solar cells do require a charge controller.

 

[JTQ]

Another issue with getting best performance from a solar cell is to make sure there are no "grass shadows" on it.

So often you see cells placed directly on the ground where the odd shadows from blades of grass are cast on one or more cell elements.

This has a totally disproportional effect on the cells current output relative to the area shaded.

A simple solution is to place the cell on a spare bit of awning skirt such as that provided for bridging the wheel arch, as that will hold the stray blades down and is weather proof.

This effect is worse with small cells; some modern cells incorporate a diode network to lessen the loss from shadows like from flies etc but placing the cell on something to eliminate the grass effect is very worthwhile.

 

[James_374408700]

I would try it with a charge controller.

Try www.aireandsun.co.uk Steca Solsum 5amp @

 

[EmmanuelMuldoon]

I use one of these with a sunsei regulator & it works fine. You say the "battery loses charge every time you use it"; are you connecting it correctly, sounds to me like it's the wrong way round??

 

[Guest]

Couple of other points. Most solar panels do not like being walked on, I wouldn't be laying one on the ground.

Roof mounting is the best option, permanent or temporary when pitched. (Use velcro or simlar to secure if temp fixing)

Friends had large solar panel that has legs so that it can be stood and angled towards the sun, they were told time and time again to roof mount it. About hree weeks ago it walked when they caravanning near Javea. They contacted their insurers who have rejected the claim.

 

[PopRudd]

Scouser,

I have used solar pannels for many years now and remenber reading somewere, if you leave the pannel connected to the battery ( without a suitable regulator ) after the sun goes down,or at least when the pannel is not charging the battery, it goes into reverse. In other words the battery starts to discharge.

My 15w pannel is used on a 110amp battery all year around in storage no problems.

Pop.

 

[EmmanuelMuldoon]

Scouser,

I have used solar pannels for many years now and remenber reading somewere, if you leave the pannel connected to the battery ( without a suitable regulator ) after the sun goes down,or at least when the pannel is not charging the battery, it goes into reverse. In other words the battery starts to discharge.

My 15w pannel is used on a 110amp battery all year around in storage no problems.

Pop.

Pop, Most panels thesedays have a series diode to prevent this happening. The Maplin the OP has certainly does.

 

[Dustydog]

Couple of other points. Most solar panels do not like being walked on, I wouldn't be laying one on the ground.

Roof mounting is the best option, permanent or temporary when pitched. (Use velcro or simlar to secure if temp fixing)

Friends had large solar panel that has legs so that it can be stood and angled towards the sun, they were told time and time again to roof mount it. About hree weeks ago it walked when they caravanning near Javea. They contacted their insurers who have rejected the claim.