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| Alternative Energy Discussion relating to the design and implementation of alternate energies. |
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| New Member | Hi there... Im new at the forum, and i really dont know if this kind of threads are allowed in this forum. I tought about a project that im trying to build, but my problem is i dont know a thing abut electronics (trying to learn :S), i was wondering if you guys could take a look to my project and give me something like a "guide line", so i know what kind of information should i "dig" to make this. What i want to do, is find a way to charge my nokia battery (BL-5C), and for that i want to use solar energy. I've reccentrly borrowed 4 solar cells from a friend, he told me that the output of those cells was "2v/500mA" each, at bright light. Here is the picture -> solar.jpg The transformer from nokia tells me that the AC input is 100-240V 50-60Hz/180mA DC Output is 5.7V/800mA --- And now im a bit confused, i think i have to find a way to "control" the output of the cells to do not exceed the 5.7v/800mA ... right? What exactly do i need, to do that? I need a "name of something that lets me do it", so i can dig information about it. Hope someone can help me in this... Thanks Reguards OpPoSiTe PS- Sorry about the bad english |
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| Guest | Current regulation won't be a problem as the solar cells won't output more curent, and a simple linear power supply should do the rest. http://www.national.com/pf/LM/LM317.html |
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| Experienced Member | Hello Paul Even if all the solar cells were put in series, this would only give a max output of 8 volts. If I'm not mistaken the lm317 needs a differential voltage of at least 3V (8-5.7=2.3). Furthermore, that would only give a curent of 500mA not the required 800mA. Also, isn't the output voltage usually rated with no load, making the situation worse. Hello Opposite Quote:
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| New Member | Thanks both of you for answering, and thanks for the answers, thay sure gave me something to search for Quote:
Here is the picture -> solar.jpg (Silly draw, hope you understand it) If i am correct, my output at bright light would be 8V/1000mA (Am i right?) Quote:
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Did some "googleing" about this kind of project and found this: http://www.fizzl.net/projects/solar_charger/ Obviously that aint lithium ion battery, the mobile is way too old, but since the transformer is the same for all nokia phone (i think), the process woulnt be so different, right? Once again, thanks both of you Reguards OpPoSiTe PS- Sorry about the bad english | |||
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| Experienced Member | ![]() Those diodes are connected backwards so it'll discharge the batteries into the solar pannels possibly damaging them. I personally wouldn't charge Li ion batteries with a simple circuit like this, however I've heard that they'll be fine providing the current is very low. |
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| Experienced Member | Hello Opposite DO NOT follow the project in that link. That person clearly knows nothing about charging batteries, especially lithium ions. Quote:
It should also be noted that niether of us has a clue what additional charging circuitry is included in either the phone or the charging adapter. Well it is 6:25AM here and way past my bedtime so I must go for now. It looks like you have enough research to keep you busy for a while anyways. Some other battery types are a bit easier to charge. You may want to make something like this instead. I think it would be a little more versatile, and more simple to design. Just my 2 cents. | |
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| Experienced Member | Hello Hero999 I concur. If you read that guys remarks you'll see that it doesn't even work for him. It just doesn't add up. goodnight....errr moorning |
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| Experienced Member | A lithium battery is a hazzard if it isn't charged correctly. You don't want to be near the extremely hot white flame from an overcharged lithium battery burning.
__________________ Uncle $crooge |
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| Experienced Member | "What i want to do, is find a way to charge my nokia battery (BL-5C), and for that i want to use solar energy. I've reccentrly borrowed 4 solar cells from a friend, he told me that the output of those cells was "2v/500mA" each, at bright light." You need a single diode. thats it !! but check if the cells are in series or parallel, or individual, they look individual They should be hooked in series with a diode pointing twards the battery plus from the plus of the series cells. I dont believe that overcharging is a problem .And the voltage need not be regulated because the battery will regulate the voltage . |
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| Experienced Member | Quote:
__________________ Uncle $crooge | |
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| Super Moderator | Quote:
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| Experienced Member | Quote:
The battery is a dinky little thing for a cell phone. It won't take much over-charging current to set off the chemical reaction: Overcharging causes rapid oxidation which produces heat, which causes even quicker oxidation which produces more heat, which ruptures the case and lets oxegen in to make it really hot! Here is what Analog Devices says about lithium battery charging:
__________________ Uncle $crooge | |
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| Experienced Member | Quote:
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| Experienced Member | Hi, I do not believe that overcharging or undercharging by as little as 1% would be a problem. I think they are mistaken or lying. John
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| Experienced Member | All semiconductor makers have Li-Ion battery charger ICs with very good accuracy. Linear Technology has one with 0.35% accuracy. They don't want the battery to burn. Green Batteries have a FAQ about Li-Ion batteries:
__________________ Uncle $crooge |
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