what to do with 4 1.8W solar cells

[Simon]

I ordered a pack of solar cells on ebay. I actually ordered 36 but have received 40. Well I'll only need 36 to make a standard 12 V (well 17.5-18V) panel.

What shall I do with the other 4 ?

Creative suggestions welcome. These are amazingly light, the listing claims 6.5g per cell and yes they feel well fragile. I'm curious as to what they are made of as some look like "papermashay" so providing the support system is very light the overall panel will be very light.

My instinctive thought was make some portable power packs with them, use 1 or more with a boost converter to produce anything up to 12 volts.

My plan for the 36 and the many more that should follow is to make custom fit panels for my shed and then my outhouse. The outhouse will be an interesting one because it has a flat roof and I will need to put the panels on a 45 degree frame. Having individual cells makes this very easy as I can have long thin panels that will not stick up much and not have so mauch trouble in the wind or be an eyesore. A possible development will be to put each cell in it's own "leaf" and make a mechanism to tilt the whole row at the sun as it does round. I expect that's what I'll use the 4 spare panels for - prototyping.

[ShiftPlusOne]

How much current can they provide (on a sunny day, aimed directly at the sun)?

They sent 40 because they expect a few to break in transit.

[Simon]

they allegedly make 3.6amps (I say allegedly because they are about the same size if not smaller than the ones in my 50W panel that is declared at well under 3.6 amps)

Well you see they have listings for 36 and 40 so my guess is that they made a mistake in packing

[Zero999]

Just use them all and connect them to a buck SMPS to convert the excess voltage into current to charge the batteries more.

[ShiftPlusOne]

I think if you would've ordered 40, they'd send 44

Anyway, I'd make some sort of battery charger.

[RayJones]

Have you started soldering them yet?

I tried with similar cells and admitted defeat after damaging the cells.
I got to 9 and destroyed 4 in the process - not a good start so I cut my losses and bought a proper panel.

In other words, don't bank on having 4 when you're done!

[Simon]

Just use them all and connect them to a buck SMPS to convert the excess voltage into current to charge the batteries more.

well at the moment I'm covering the shed roof and so need to match them all as they go into the grid tie inverter, the current panels are 17.5 and 18 V, I think the losses in the converter would offset the gail in this type of use.

Have you started soldering them yet?

I tried with similar cells and admitted defeat after damaging the cells.
I got to 9 and destroyed 4 in the process - not a good start so I cut my losses and bought a proper panel.

In other words, don't bank on having 4 when you're done!

Fair point, I do have 2 x 20W and 1 x 50W panels at the moment, I decided to experiment in making up my own. This is like in the case of covering the flat roof making custom long thin panels is ideal

[Simon]

anyone have tips on sodering ? I can see that fragile as they as yes they will just crack if pressed hard

[Zero999]

I think the losses in the converter would offset the gail in this type of use.

Yes, I think youre right there.
36/40 = 0.9 = 90%

A typical converter would also be 90% efficient. However, you go gain something: it should work at lower light intensities.

[Simon]

yea well I'm not sure a SMPS in parallel with other solar panels is going to go down well, anyway if the other panels drop out having the 40 cell one still performing will be of little help as it will just feed into the other 3 and not be enough on it's own to boot the MPPT controller in the GTI. it would work if I did the whole shed roof like that. I'm considering making each cell into a little panel or doing them in 1-2 Volt blocks so that over time I can arrange them as I please and it is easier to solder them and stick them down on their own than in a large array. If these are successful I'll do more so I could have 24V panels feeding the GTI (Takes up to 28V) and later if I had a larger system rearrange for 30-50 volt systems

[Simon]

right well here is the plan: I'm scrapping the idea of the shed roof, it get's partially shaded by the house and is falling apart. I'll start on the flat outhouse roof instead.

Now here is the plan. I'm going to make a single panel out of each cell. No I'm not nuts in making myself so much work. Firstly these will have to be put on a frame at 45 degrees (or whatever angle - preferably ajustable) so will be nice and open to picking up the wind and it can get damn windy. So by using small blocks I'm not trying to hold down a lot of "sail area" and don't need to overthink fixing. Secondly it won't be a huge eyesore.

Thirdly and much much more importantly I want to make these tilting. Now i know you think I'm truly nuts but no. I have a good 6 sq meteres of roof area and if i essentially make a miniture solar staion I will be able to track the sun and have all of the rows working off the same drivemotor. with small cells tilting individually I can get more in as with large panels I'd need to leave more spacing

Basically I'm going to put them in lines tilted with a lever pointing down from each one. A bar will run the length of the rows connected to each lever so that but pushing it left and right I tilt all of the cells at once, this can be connected to the drive motor to shift them in the desired direction. But now if I have all of these parallel rows All I need to do is run another bar connecting all of the bars from the rows together and so with one motor move 6 sq metres of panel. Yes I have such a motor from MFA who make small powerful motors for this sort of thing with built in gear boxes and providing an impressive torque.

Well not sure how long this will all take. the advantage is i can just keep adding it as I go and making up my own cell arrangements can specify my own voltages, so yea I'll be midway between standard 12 and 24 volt panels making the best of my 28V GTI and less power loss over transmision line that's not that long anyhow but I bet the GTI is more efficient with a higher voltage

[Uncle Vernon]

anyone have tips on sodering ?

http://www.sodastream.com.au/auretail/FAQ.aspx#CarbonatingBottles you could try these! 

[Simon]

yea typo, I meant soldering