looking for input on dealing with shade

[solarexperimenter]

OK, newbie here... My project is entirely just for fun and learning purposes. I built a little temperature logger (a common first project, lol) and wanted to experiment with how well I could run it off solar outside. Note that I'm doing everything from scratch. I want it to be a really good learning experience. I ordered two of these cheapies: http://www.parallax.com/product/750-00030

What I need is to stay above 5V. Now, in full sun, these babies work great. I can even just run off one of them and it's enough to both run my board and charge some batteries at the same time. As long as I have a couple of hours of full sun per day, my circuit runs seemingly indefinitely. The batteries kick in at night and a diode cuts off the panel.

OK, now the problem is that starting at this time of year and lasting until around March, the sun moves just enough that I can no longer get any full sun at all. I live in an apartment building and my balcony is recessed and north-facing, and I'm in the northern hemisphere. Sooooo, starting about 2 days ago, I started losing power. The positive side of this is that clearly, things really were working great before and it wasn't just my imagination. Without the panel(s), my circuit dies in about 24 hours when the batteries run out.

I have tried putting the panels in parallel and series but got nothing. As soon as I turn my board on with a single panel, I go from about 5ish volts down to 1.4V. Shade KILLS it. In series, I get about 11V open circuit, but around 2V closed. Ouch, but at least it's going up? I could conceivably just keep adding more and more of these things, although I'll have to build a buck converter for when spring eventually rolls around or my batteries will take a serious hit.

So what I'm looking for thoughts on is just how to deal with shade. Just keep adding more panels? I worry that I might fill my balcony up and still not be able to run my tiny little board. Is there something *else* I can do?

I thought of jumping up to a better quality panel, such as *maybe* this: http://www.parallax.com/product/750-00032
But I don't know if it is actually better. I don't know how to compare them. They all give their open and closed circuit voltages and aperages, which is great, but those are based on full sun.

I'm open to other products, too. Parallax is just convenient for small projects.

[Sunking]

This is going to be fun!

[solarexperimenter]

This is going to be fun!

Did I pick the wrong forum? I'll gladly leave if so.

[SunEagle]

OK, newbie here... My project is entirely just for fun and learning purposes. I built a little temperature logger (a common first project, lol) and wanted to experiment with how well I could run it off solar outside. Note that I'm doing everything from scratch. I want it to be a really good learning experience. I ordered two of these cheapies: http://www.parallax.com/product/750-00030

What I need is to stay above 5V. Now, in full sun, these babies work great. I can even just run off one of them and it's enough to both run my board and charge some batteries at the same time. As long as I have a couple of hours of full sun per day, my circuit runs seemingly indefinitely. The batteries kick in at night and a diode cuts off the panel.

OK, now the problem is that starting at this time of year and lasting until around March, the sun moves just enough that I can no longer get any full sun at all. I live in an apartment building and my balcony is recessed and north-facing, and I'm in the northern hemisphere. Sooooo, starting about 2 days ago, I started losing power. The positive side of this is that clearly, things really were working great before and it wasn't just my imagination. Without the panel(s), my circuit dies in about 24 hours when the batteries run out.

I have tried putting the panels in parallel and series but got nothing. As soon as I turn my board on with a single panel, I go from about 5ish volts down to 1.4V. Shade KILLS it. In series, I get about 11V open circuit, but around 2V closed. Ouch, but at least it's going up? I could conceivably just keep adding more and more of these things, although I'll have to build a buck converter for when spring eventually rolls around or my batteries will take a serious hit.

So what I'm looking for thoughts on is just how to deal with shade. Just keep adding more panels? I worry that I might fill my balcony up and still not be able to run my tiny little board. Is there something *else* I can do?

I thought of jumping up to a better quality panel, such as *maybe* this: http://www.parallax.com/product/750-00032
But I don't know if it is actually better. I don't know how to compare them. They all give their open and closed circuit voltages and aperages, which is great, but those are based on full sun.

I'm open to other products, too. Parallax is just convenient for small projects.

As you have found, shade is as bad as night time when it comes to solar. Or in other words "no sun means no electricity".

Using a bigger wattage panel may help but if just part of it is in the shade it will probably not produce any power based on how it is built with all of the cells in series. Adding more panels in parallel may help if at least one is always in the sun. And when I mean sun I mean useable sunlight which is (depending on the season) an hour or two on both sides of Noon. Much less if the panel is facing North.

You didn't mention your battery size and with those small 1 watt panels you will not get a lot of charging during the Winter even if it gets full sunlight.

So unless you can find a safe way of mounting your panel(s) to get more sun you may be stuck with using a different way to charge the batteries and just run the temperature logger off them.

[solarexperimenter]

As you have found, shade is as bad as night time when it comes to solar. Or in other words "no sun means no electricity".

Using a bigger wattage panel may help but if just part of it is in the shade it will probably not produce any power based on how it is built with all of the cells in series. Adding more panels in parallel may help if at least one is always in the sun. And when I mean sun I mean useable sunlight which is (depending on the season) an hour or two on both sides of Noon. Much less if the panel is facing North.

You didn't mention your battery size and with those small 1 watt panels you will not get a lot of charging during the Winter even if it gets full sunlight.

So unless you can find a safe way of mounting your panel(s) to get more sun you may be stuck with using a different way to charge the batteries and just run the temperature logger off them.

Yeah I was kind of aiming that way but was hoping someone would know something I didn't know. The battery pack is whatever I want it to be. I build them. I matched this one to one panel (or one set of parallel panels) so I wouldn't have to use a converter. So it's about 6.2V. Just a tad higher than the panel on a good day. It's a very simple project. I'm really interested in learning more about solar so I built most of it myself, although not the panels. (well I had to solder them up but the cells were already put together presumably with bypass diodes already in place because I do get something in shade, just not a lot)

I was thinking of experimenting with other forms of energy harvesting, especially during winter (heat differential through windows). Fall is going to be tough, though. I'm going to have to make the logger a lot more efficient. Until now, I was thinking this was awesome - all kinds of free energy and I could be lazy with the logger and let it run all day/night at 5V and take way more readings than it needed.

[SunEagle]

Yeah I was kind of aiming that way but was hoping someone would know something I didn't know. The battery pack is whatever I want it to be. I build them. I matched this one to one panel (or one set of parallel panels) so I wouldn't have to use a converter. So it's about 6.2V. Just a tad higher than the panel on a good day. It's a very simple project. I'm really interested in learning more about solar so I built most of it myself, although not the panels. (well I had to solder them up but the cells were already put together presumably with bypass diodes already in place because I do get something in shade, just not a lot)

I was thinking of experimenting with other forms of energy harvesting, especially during winter (heat differential through windows). Fall is going to be tough, though. I'm going to have to make the logger a lot more efficient. Until now, I was thinking this was awesome - all kinds of free energy and I could be lazy with the logger and let it run all day/night at 5V and take way more readings than it needed.

First off renewable energy is never free. There are other types renewable energy available besides solar.

There is wind but it is even harder to justify in most areas due to natural low speed and high equipment costs.

Next is water. If you had a natural flowing stream generating electricity from hydro can be done as long as you don't want to run a very high electric load.

Using differential heat is another way but is very very inefficient to convert to electricity.

Mechanical power works; like a generator mounted on a fixed bicycle could be used to charge the batteries and get your exercise.

Coming back to solar. It works best when you have an open view of the Sun during the peak hours (10 am to 2 pm) of the day. Shade, clouds, snow and bird crap are things that work against you when it comes to solar.

And finally any power generated to charge batteries cost you anywhere from 10 to 15 times as much as using the power from your Utility. So when you say "free" energy, using batteries will always be more expensive than power from a wall socket.

[Wy_White_Wolf]

Yeah I was kind of aiming that way but was hoping someone would know something I didn't know. The battery pack is whatever I want it to be. I build them. I matched this one to one panel (or one set of parallel panels) so I wouldn't have to use a converter. So it's about 6.2V. Just a tad higher than the panel on a good day. It's a very simple project. I'm really interested in learning more about solar so I built most of it myself, although not the panels. (well I had to solder them up but the cells were already put together presumably with bypass diodes already in place because I do get something in shade, just not a lot)

I was thinking of experimenting with other forms of energy harvesting, especially during winter (heat differential through windows). Fall is going to be tough, though. I'm going to have to make the logger a lot more efficient. Until now, I was thinking this was awesome - all kinds of free energy and I could be lazy with the logger and let it run all day/night at 5V and take way more readings than it needed.

What? The panel VMP (Voltage Maximum Power) needs to be at least 25% higher than the battery voltage for it to fully and properly charge the battery. Most likely a big part of your problem is the battery has been destroyed from being in a state of undercharge for so long.

You battery also needs to be bigger. You should only use 20% of it's capacity in a day. Having it dead after 24 hours tells me it needs to be 5 times larger.

WWW

[solarexperimenter]

First off renewable energy is never free.

It was a joke.

[inetdog]

It was a joke.

I am sorry, renewable energy is never a joke.
He said sarcastically....

[solarexperimenter]

What? The panel VMP (Voltage Maximum Power) needs to be at least 25% higher than the battery voltage for it to fully and properly charge the battery. Most likely a big part of your problem is the battery has been destroyed from being in a state of undercharge for so long.

I'm pretty sure they are fine. Each cell is nominally rated for 1.2V, and I have 4 of them. I used a commercial charger to charge them fully just to see what they charged to fresh out of the pack. They charged to 1.5V. So... 1.5V x 4 = 6V. They occasionally charge a little higher, up to 6.2V overall. The panel delivers 6V on a good day. I am happy with this (and note that it's 25% above the advertised voltage of the cells). Now, that said, I *have* damaged some of them because I have included no circuitry to stop them from being deeply discharged, and I include no circuitry to manage the cells individually (there's always one that drains faster than the rest). Oh well. I've actually taken the deeply discharged ones out and replaced them with good ones, but the problem will persist because there isn't enough sun anymore. I'll fix it. But seriously, I don't care if the cells die.

You battery also needs to be bigger. You should only use 20% of it's capacity in a day. Having it dead after 24 hours tells me it needs to be 5 times larger.

WWW

Oh that's just because I'm being inefficient. I wanted to see how much solar energy I could waste.

Anyway, thanks. Consider the question answered.

[SunEagle]

I'm pretty sure they are fine. Each cell is nominally rated for 1.2V, and I have 4 of them. I used a commercial charger to charge them fully just to see what they charged to fresh out of the pack. They charged to 1.5V. So... 1.5V x 4 = 6V. They occasionally charge a little higher, up to 6.2V overall. The panel delivers 6V on a good day. I am happy with this (and note that it's 25% above the advertised voltage of the cells). Now, that said, I *have* damaged some of them because I have included no circuitry to stop them from being deeply discharged, and I include no circuitry to manage the cells individually (there's always one that drains faster than the rest). Oh well. I've actually taken the deeply discharged ones out and replaced them with good ones, but the problem will persist because there isn't enough sun anymore. I'll fix it. But seriously, I don't care if the cells die.



Oh that's just because I'm being inefficient. I wanted to see how much solar energy I could waste.

Anyway, thanks. Consider the question answered.

Maybe finding an apartment on the sunny South side will help.

I wish we could provide a better answer for you. While I really support the use of solar pv there are limitations to it's use.

[Sunking]

What? The panel VMP (Voltage Maximum Power) needs to be at least 25% higher than the battery voltage for it to fully and properly charge the battery. Most likely a big part of your problem is the battery has been destroyed from being in a state of undercharge for so long.

You battery also needs to be bigger. You should only use 20% of it's capacity in a day. Having it dead after 24 hours tells me it needs to be 5 times larger.

WWW

None of any of this matters, with a 1 watt panel he cannot even charge a watch battery up. The whole discussion is silly and far from any reality of what is physically possible. .

[Mike90250]

Another rare case where a large (50-100w) amorphous panel may work. They produce better in low light, but only a 15 year lifetime

[solarexperimenter]

Maybe finding an apartment on the sunny South side will help.

I wish we could provide a better answer for you. While I really support the use of solar pv there are limitations to it's use.

It's OK. This has been a fun project. I knew it would eventually fail due to lack of sun but I was hoping I could maybe just build the array bigger and bigger and keep being able to be lazy with the electronics, but there's a limit to that as well.

None of any of this matters, with a 1 watt panel he cannot even charge a watch battery up. The whole discussion is silly and far from any reality of what is physically possible. .

Hate to break it to you, but they charged. Fairly easily in full sun, too. I was skeptical until I tried it. I put a load on the batteries and the voltage never changed over multiple days, except in the mornings. So, they charged. And why wouldn't they? They have an extremely low ESR. Why wouldn't they charge? edit: to be fair, the logger doesn't actually draw a lot of power. I think I was wrong about the "dead in 24 hours" bit. I forgot I was away for a couple of days and when I tried to remember the last time it communicated, I think I failed to remember those extra days. Oops. I wasn't being especially scientific about it.

Another rare case where a large (50-100w) amorphous panel may work. They produce better in low light, but only a 15 year lifetime

Or I can just start focusing on making the logger actually efficient. I know, it's a boring solution, but it'll work.

[Sunking]

Hate to break it to you, but they charged.

It is all very simple 5th grade math. What voltage and amp hour rating are these batteries?

Just a single AA NiMh is 1.2 volts @ 2500 mah takes a 10 watt panel to charge in a day.