None.
Matter of how you treat them.
Batteries tend to explode on how you use them.
Caps can explode on how you power them.

 

On to bigger and better things. Batteries or capacitors. Which is more safe? Keep in mind that I live in Florida and it stays damp here.

Either one is quite capable of killing you if you don't know what you are doing.

 

[snip] Batteries or capacitors. Which is more safe? Keep in mind that I live in Florida and it stays damp here.

You'll be able to store more energy in batteries, but the downside to lead acid batteries is that the cells will experience sulfation if allowed to be in a discharged state too long. Dampness shouldn't cause problems with batteries because the voltage is low. You don't want standing water to collect and touch both terminals because water with contaminants conducts.

I for one am not here to judge you or your circumstances. I'll offer whatever information I can to help with your circuit questions.

 

Batteries tend to explode on how you use them.

Unlikely to explode while being charged from solar cells or being discharged unless you short the terminals.

UnityInDiversity - keep the batteries topped with distilled water. If you don't have access to any, use your fresnel lens to boil water and collect the condensation. That'll be close to pure.

You'll also want to get a hydrometer to measure the specific gravity for each cell.

 

Thank you dl324. That is the exact kind of explanation I am looking for.

Lead acid. That would be a car battery, right?

 

Lead acid. That would be a car battery, right?

Cars, lawn tractors, motorcycles. These are usually "wet" batteries. Other battery operated equipment could have SLA (Sealed Lead Acid batteries) which are maintenance free.

Don't mix the types because they have different charging requirements; though you'll probably not be concerned with (or be able to be) if you're using salvaged solar cells for charging.

Nominal voltage for lead acid is 2.1V per cell, so a 12V battery should read 12.6V when near full charge. Charging voltage should be around 13.8V.

Solar cell voltage will depend on the amount of light it absorbs and you'll want a rectifier diode between the solar cells and batteries so the batteries won't discharge when the solar cells aren't producing enough voltage. Solar cells output more current when they're near their open circuit voltage.

 

What is open circuit voltage?

 

A battery is much better than a capacitor for storing any significant amount of energy. I would say safety should not be a particular issue if you take normal care with the design and construction.

NiMh batteries are good but tend to be expensive if you want to store significant amounts of energy.

Lead acid batteries give good storage for the buck but tend to be bulky and heavy but that may not be a problem for your application. The best for that purpose are those designed to tolerate a deep discharge (deep cycle types). The sealed type are easier to handle and maintain.

Harbor Freight has some fairly low priced (for the amount of power they generate) solar cells for sale.

How much energy do you think you want to store to begin with?

 

What is open circuit voltage?

Voltage with no load. As you apply a load to the solar cell, it's voltage will drop.

 

Not a lot, at least I do not think so, at least to start. My primary goal is to light up my living space at night and to charge my electronics so that I do not have to spend half of my day sitting around waiting for them to be done. My vegetable garden is suffering for my abcence.

 

I don't know if this would work, but one idea would be to go around and ask people if they have any old solar yard lights that they don't want, working or not. I don't know about the newer models, but the older ones actually had a NiCd AA battery in them. What you could do is repair and modify a whole bunch of them, like maybe a hundred, or two. What I would do is disconnect the LED inside, or somehow make it so that the LED never turns on when it gets dark. If you have land for a garden, you might be able to set them all out, and if it takes several days each to recharge the battery inside, so be it. You could harvest charged batteries each evening, just like a crop, enough to power your lights or recharge your phone.

If you can scavenge a battery holder that will hold 4 cells, and a connector appropriate for your phone, it should be possible to make a phone charger.

Although it sounds like you have a place to stay, I receive that you are homeless, so it might be a good idea to keep everything very simple. As such, if it were me, I wouldn't try to have good lighting. I would use one yard light as a lantern if I needed to get around, or read something short, but I would basically try to do everything during the day, and just sleep when it got dark. I've done that on occasion when camping, and it is kind of boring compared to city life, but it's also peaceful.

 

Maybe some kind of physical energy generation that didn't have to been done for long, charging a super capacitor? If you had a bike you could use a small dc motor as a charging device. If you could focus the frensel on something like this...
http://en.wikipedia.org/wiki/Thermoelectric_generator
Are you near running water?
Maybe you could build a simple Stirling engine and charge some recycled lead acid batteries.

 

Two problems with, "Supercapacitors".
1) They are miserable power storage devices compared to any battery.
2) They are basically impossible to find in a Dumpster, so they will cost money.

 

My primary goal is to light up my living space at night and to charge my electronics....

OK, that helps define the amount of juice you need. I assume you need a modest amount of light just to see your way around and maybe a higher intensity in a small area, for reading or such. How many hours of light do you need each night? Do you already have the lights? (If so, let us know what they need.) How much power do your other gadgets need, in terms of voltage and mA-hours?

Let's see if we have the other facts: You live in Florida and you have NO power grid access. (This last fact is critical. If you can plug in twice a week, the project is a lot different.) You have next to nothing to start your project except maybe some solar panels from solar lights. Your source of additional materials is uncertain and opportunistic - i.e., the dumpsters.

I think the solution is a modular system that can expand easily as you acquire more pieces. Roderick nailed it in #31. It should be fairly easy to find "spent" solar lights. Once you learn about them, you'll be able to tell if the panel is good, the condition of the battery and so on. As Roderick described, set up a little farm of solar battery chargers. You can either harvest the AAs or AAAs every evening or disable the lighting circuit so they don't waste power at night.

You're unlikely to find a large PV panel cast away, although I have gotten some nice panels from solar-powered Christmas lights that had failed and been tossed out. That would be a sweet find for you but not likely to happen.

If you can get your hands on an old car battery with decent life left in it, that can open up some options. But it will require some help and circuitry to be useful. We can provide those details if/when this becomes a viable option for you. At some point you might want 120V AC, and for this you'll need an inverter, the thing folks use in their cars to provide household current. Out of the question?

 

Maybe some kind of physical energy generation that didn't have to been done for long, charging a super capacitor? If you had a bike you could use a small dc motor as a charging device. If you could focus the frensel on something like this...
http://en.wikipedia.org/wiki/Thermoelectric_generator
Are you near running water?
Maybe you could build a simple Stirling engine and charge some recycled lead acid batteries.

I have an old beach cruiser frame that I stripped most of the parts from to get my boyfriend's bike working. That leaves me exactly an intact frame, the rear rim, the chain and the pedal sprocket. Enough for the generator you mentioned? My question would be what defines small for a dc motor in this application and in what type of device am I likely to find one?

I also skimmed the article on the thermoelectric generator and it is at least worthwhile to look into as it can be used in tandem with the solar to assist in maximizing energy output.

 

I don't know if this would work, but one idea would be to go around and ask people if they have any old solar yard lights that they don't want, working or not. I don't know about the newer models, but the older ones actually had a NiCd AA battery in them. What you could do is repair and modify a whole bunch of them, like maybe a hundred, or two. What I would do is disconnect the LED inside, or somehow make it so that the LED never turns on when it gets dark. If you have land for a garden, you might be able to set them all out, and if it takes several days each to recharge the battery inside, so be it. You could harvest charged batteries each evening, just like a crop, enough to power your lights or recharge your phone.

If you can scavenge a battery holder that will hold 4 cells, and a connector appropriate for your phone, it should be possible to make a phone charger.

Although it sounds like you have a place to stay, I receive that you are homeless, so it might be a good idea to keep everything very simple. As such, if it were me, I wouldn't try to have good lighting. I would use one yard light as a lantern if I needed to get around, or read something short, but I would basically try to do everything during the day, and just sleep when it got dark. I've done that on occasion when camping, and it is kind of boring compared to city life, but it's also peaceful.

I actually have a growing collection of solar lights from doing just what you said. Well that and my dumpster diving expeditions (one reason why a reliable flashlight is necessary) I have also started packratting small electrical devices (mostly toys) and stripping out their circuit boards for useable components. I also have all of the circuit boards from the television I salvaged the lens from so, I have a lot of odds and ends to pick through.

As for the solar lights I have taken a few of them, cut the LED out completely and spliced the remaining wires; sealing the splices with shrink tube. What I was most unsure about was how to further proceed with wiring them together to most effectively serve my needs. It is also worth mentioning that I salvaged the battery compartments from all toys requiring either AA or AAA batteries in hopes that they could be used either as-is or modified to hold the batteries that I want to charge.

As for the light consumption, my boyfriend is the night owl. I am usually out before 10. I need the light for my early morning garden tending and for that I have been given a head-lamp like those used for spelunking. I also have a bevvy of different projects that each need small amounts of electricity and I have had to shelve them until I can provide that energy which brings me to a new question. What if I wanted to wire said solar lights to provide energy directly to a water pump such as would be used for a hydroponic garden?

Hmm...time to go read some text on the math involved in all of this...

Thanks!!!

 

An automobile alternator would work with the bike parts you have to generate a small amount of electricity and charge a 12V lead-acid battery. You could use a V-belt around the bike rim to drive the alternator.
An alternator can be readily found in an auto junkyard, just make sure it's one that has a built-in regulator.

 

OK, that helps define the amount of juice you need. I assume you need a modest amount of light just to see your way around and maybe a higher intensity in a small area, for reading or such. How many hours of light do you need each night? Do you already have the lights? (If so, let us know what they need.) How much power do your other gadgets need, in terms of voltage and mA-hours?

Let's see if we have the other facts: You live in Florida and you have NO power grid access. (This last fact is critical. If you can plug in twice a week, the project is a lot different.) You have next to nothing to start your project except maybe some solar panels from solar lights. Your source of additional materials is uncertain and opportunistic - i.e., the dumpsters.

I think the solution is a modular system that can expand easily as you acquire more pieces. Roderick nailed it in #31. It should be fairly easy to find "spent" solar lights. Once you learn about them, you'll be able to tell if the panel is good, the condition of the battery and so on. As Roderick described, set up a little farm of solar battery chargers. You can either harvest the AAs or AAAs every evening or disable the lighting circuit so they don't waste power at night.

You're unlikely to find a large PV panel cast away, although I have gotten some nice panels from solar-powered Christmas lights that had failed and been tossed out. That would be a sweet find for you but not likely to happen.

If you can get your hands on an old car battery with decent life left in it, that can open up some options. But it will require some help and circuitry to be useful. We can provide those details if/when this becomes a viable option for you. At some point you might want 120V AC, and for this you'll need an inverter, the thing folks use in their cars to provide household current. Out of the question?

Funny you should mention Christmas lights as I was bemoaning the want of some that ran off of solar (I did not know such a thing existed) I have two strings of the LED (plugin) type ones and if I could only power those, they and some white paint would provide all of the light I need, at least on the inside.

 

An automobile alternator would work with the bike parts you have to generate a small amount of electricity and charge a 12V lead-acid battery. You could use a V-belt around the bike rim to drive the alternator.
An alternator can be readily found in an auto junkyard, just make sure it's one that has a built-in regulator.

I had looked into that option and was under the impression that, once powered, an alternator required something like 10hp in order to turn it and create the charge needed to power the battery...

 

Sorry, I'm very confused about the constraints of this project. If you can consider a 10HP motor, then getting enough power is not a problem. Forget about solar and water (and wind too). There are commercial generators you could consider. So far it sounds like you'd want the smallest one available, and it would run only intermittently as needed. A small generator, a 12V battery and an inverter would provide you a mini-grid with more than enough juice for your modest needs.