looking for input on dealing with shade

[ZoNiE]

If you live in a large city, look on craigslist, find a panel around 100W or so, buy it. there are always new and used panels. Sometimes they come off of rental equipment, sometimes leftovers from solar installers. Pay a buck or less per watt.

Buy a cheap PWM 12V charge controller.

Get a car battery, or lawnmower or motorcycle 12V battery. Your application is not that much of an energy draw smaller may be better.

Build or buy (from china on ebay) a 12-5V DC-DC converter that has sufficient ampacity for your needs. If your project is small enough, a simple 7805 voltage regulator with a heat sink from Rodeo Shark may be all you need. Heck, even a voltage divider.

There you have a nice little solar power system that you can use for tons of little electronic projects.

Those $9 1W Panels are a waste of money. $9 per watt? Fughetabout it. Those are for calculators and the like.

The 18W panel is nearly as bad.

If you have a harbor freight, they have a little 10 foot LED light set with a battery and 3"x3" solar panel for $10. It may work. I bought one for kicks and put it on my patio, and it stays on all night. You could hack the parts out of it.

[Mike90250]

Look for some shade panels on ebay, maybe they exist, Solar panels require direct sun.

[SunEagle]

Using his math, it looks like his panel would take around 4 days to charge a 2500 mAh 6v battery on days with 4 sun hours, if it didn't have to power his logger at the same time. Does that sound about right? I'm trying to see if I understand this.

Using math that 1 watt 6 volt panel with a 0.17amp output would take over 14.7 hours (about 4 x 4 hour days) to charge that 6 volt battery. But in reality since a 6v battery needs over 6volts to charge he would have had to put at least two of those panels in series to charge at all.

Now that 10 watt panel could have charged his 6 volt 2500ma battery in one day if he gets a lot of sunshine. Since he is now getting shade the charge time would extend into days.

[sdold]

Using his math, it looks like his panel would take around 4 days to charge a 2500 mAh 6v battery on days with 4 sun hours, if it didn't have to power his logger at the same time. Does that sound about right? I'm trying to see if I understand this.

[russ]

You said it was physically impossible for my panel to charge even a watch battery. Turns out it isn't physically impossible at all.

2500mAh/0.17A = 14.7 hrs =/= inf. They'll charge. You said it was impossible for them to charge. It obviously isn't. 10W panel: 2500mAh/580mA = 4.3 hrs =/= 1 day. Even if you start adding in losses, it does not come up to a day.

Anyway, this has been fun. Time to figure out how to kill the notifications.

Goodbye and have fun- as you don't want to listen to someone who knows but to believe your own BS you must lead an "interesting" life.

[solarexperimenter]

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.

You said it was physically impossible for my panel to charge even a watch battery. Turns out it isn't physically impossible at all.

2500mAh/0.17A = 14.7 hrs =/= inf. They'll charge. You said it was impossible for them to charge. It obviously isn't. 10W panel: 2500mAh/580mA = 4.3 hrs =/= 1 day. Even if you start adding in losses, it does not come up to a day.

Anyway, this has been fun. Time to figure out how to kill the notifications.

[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.

[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.

[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

[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. .

[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.

[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.

[inetdog]

It was a joke.

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

[solarexperimenter]

First off renewable energy is never free.

It was a joke.

[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