a solar 3ds charger

Discussion in 'The Projects Forum' started by sonicslayer, Mar 12, 2012.

  1. sonicslayer

    Thread Starter New Member

    Mar 12, 2012
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    i'm a gamer and i love to play my 3ds but on the long trips the battery just does not last long enough 4 my taste and i don't want to a better battery for it so what i would like to do is make a solar usb charger with a battery back so that i can play it on long trips and not worry about it dying .i know what u r going to say get a car charger but i tried it in my car and it didn't work and besides a solar charger can be taken anywhere and the portiability is ehat i like more then any thing about so can any one help me thanks
     
  2. wayneh

    Expert

    Sep 9, 2010
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    I think to be useful you'll need a panel that could charge a battery pack in, say, 2 hours in full sun. Pick a different time if you like. The time available and the battery capacity in mAhours define how big the panel must be, in terms of mW. I'd add maybe 50% for the various losses. I forget what modern panels are capable of but it's something like 1W for a 4-inch square panel.

    Then you'll need to consider voltage. It seems like a maximum panel voltage of about double the battery voltage is common. A panel is most efficient when loaded to about 80% of its peak voltage, but I think designers go higher to sacrifice efficiency for shorter charging times while the sun is at less than full.

    To hook it all together, you'll need at the very least a blocking diode to prevent reverse current when the panel is dark. You'll probably also need overcharge protection to keep your panel from ruining your battery. For this you'll need to know a lot about your battery's chemistry and find the appropriate charge controller for that kind of battery. This might be as simple as a 5v voltage regulator to give you "usb"-like output, to let the device then handle the charging. That will waste power (eg. you feed it 10v and it puts out 5v, wasting the other 5 as heat) but is really simple to hook up.
     
  3. sonicslayer

    Thread Starter New Member

    Mar 12, 2012
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    thanks the back of the wall charger says that the out put is 4.6 v and my solar charger inside just under a light is 5.20 dcv so what else would it take to make what i want to make
     
  4. wayneh

    Expert

    Sep 9, 2010
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    Hard to say, since it's impossible to guess how your test compares to full sun. The voltage you measured is no more than the absolute minimum you'd need, though, so it's a yellow flag. You need a blocking diode, and it will drop about 0.6V across itself. Does your charger give a current rating, like 1A or 500mA?

    Voltage of an un-loaded panel, without other information, is not useful. A tiny panel or a giant one might both produce the same voltage. You need to compare the power output of the panel, in mW or watts, and compare that to the battery power storage capacity, usually given in mAh. One thousand mAh at 5V in the battery is the same as 5W-hrs from the panel. So if you have a 1W panel, you'd need at least 5 hours of optimal operation to give you a full charge. If the math shows your panel requires 30 hours, for instance, to give a full charge... I question how satisfied you'd be with that.
     
  5. sonicslayer

    Thread Starter New Member

    Mar 12, 2012
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    well i got to test it out side and i got 9.85 dcv max so i think that is pretty good but i think it will work if i get min that i need in house light and more then that outside so i know i will need a blocking diode, a 5v regulator, a battery pack, 5v worth of batteries and, a female usb cable i think that is all i will need but i have no idea how to hook it up
     
    Last edited: Mar 13, 2012
  6. wayneh

    Expert

    Sep 9, 2010
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    3,060
    The blocking diode goes between the solar panel and the battery. Most folks put it on the positive path and directly connect the grounds together. It's unlikely your panel is big enough to damage your batteries, so it's probably OK to have no controller between the panel and the battery. You should check these assumptions, though. Batteries are too expensive to ruin, and it can even be dangerous to overcharge them.

    If your battery pack voltage exceeds ~5.2V or so, then you need a regulator to reduce it to 5v, to simulate a USB power source. This creates another problem: The regulator itself needs a source that is at last 1.2V higher than the output, ie. >6.2v. You can find regulators that require less, and these are called low-dropout or LDO regulators. Not as easy to find as the 7805, which you can get at Radio Shack or even find in many scrap electronics.

    The voltage regulator goes between your battery and the USB cable. Look up the datasheet for the 7805 voltage regulator and you'll find lots of examples. Look up the pinout of a USB cable so that you get the polarity correct. You'll be using only the two outer pins, but it's easy to mix them up.

    You may run into one other problem. While USB power is on the two outer pins, there can be a data "handshake" on the inner two pins that sets the charging level. Your 3ds may not like having a dead or stupid power supply and might refuse to run off your rig. An iPod, for instance, needs to see certain voltages on the data pins to initiate charging. You can research this problem for your 3ds, as I'm sure you're not the first to be playing around with this idea.
     
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