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USB, DC & Solar Lipoly Charger

Created by lady ada

Last updated on 2016-10-11 09:31:57 PM UTC

Summary of content (40 pages)

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USB, DC & Solar Lipoly Charger Created by lady ada Last updated on 2016-10-11 09:31:57 PM UTC
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Guide Contents Guide Contents Overview FAQ Solar Charger Preparation Installing the Capacitor Solar Panel Preparation Splice or Adapt? 7 9 9 Voltaic Panels with 1.
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Overview Make your projects to go green this summer with our specialized USB/Solar Lithium Ion Polymer Battery charger! This charger is a very unique design, perfect for outdoor projects, or DIY iPod chargers. We've spent over a year testing and tinkering with this charger to come up with a plug and play solution to charging batteries with the sun and we're really pleased with what we ended up with. Easy to use! Pick up any of our many 3.7V/4.2V LiIon batteries (http://adafru.
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Charge with 5-6V DC, USB or 6V solar panel! Too dark out? Use a USB mini-B cable (http://adafru.it/260) or a 5V DC adapter (http://adafru.it/276) Automatic charging current tracking for high efficiency use of any wattage solar panel Use any 6V solar panel (6V seems to work best, 5.5V may work, 5V does not work) Three color indicator LEDs - Power good, Charging and Done Low Battery Indicator (fixed at 3.
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FAQ Is this a MPPT tracker? This is not a true MPPT tracker, for information on why we did not design it as a true MPPT, read our design notes! (http://adafru.it/aN7) Why didn't you make this an MPPT? For low power solar charging of lithium ion's, its not necessarily a better way to charge.For information on why we did not design it as a true MPPT, read our design notes! (http://adafru.
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Solar Charger Preparation Installing the Capacitor The first thing to do before starting to charge with a solar panel is to install the large filtering capacitor. This capacitor is necessary to stabilize the panel a little, and since we're going to charge with a lot of current, the capacitor needs to be pretty big. There is a spot on the PCB for the capacitor, you can of course install it directly there by soldering the wires of the capacitor into the pads.
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Next you will have to connect up your solar panel. Panels sometimes come 'bare' (no wires), with just wires, or with a connector of some sort. You may need to splice a connector onto the panel to match the 5.5/2.1mm (or 4mm on older charger) DC jack on the adapter. © Adafruit Industries https://learn.adafruit.
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Solar Panel Preparation Splice or Adapt? The first verison of the solar charger came with a 4mm DC barrel jack on it. On older versions (4mm) it would come with a converter cable. If you have a newer v2 charger (June 2013+), connect a 2.1mm Terminal Block Adapter (http://adafru.it/369) onto the panel using basic wires, or a1.3mm to 2.1mm adapter cable (http://adafru.it/2788) then plug that into the 2.1mm adapter.
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Other 6V Solar Panels If you have a panel with something other than 2.1mm or 1.3mm connector, you'll need to remove any existing connector. Cut off whatever connector is on © Adafruit Industries https://learn.adafruit.
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Method 1 For this you'll need a 2.1mm Terminal Block Adapter (http://adafru.it/369) but its really simple. Just open up the screw terminals, slide the red wire into the + hole and the black wire into the - hole and retighten! Now you can just plug it directly into the charger (or adapter cable). © Adafruit Industries https://learn.adafruit.
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If You Have a Pre-2013 Solar Charger This method is a little tougher, but results in a nicer cable. You'll need some heatshrink as well as some item with a 2.1mm DC barrel plug (like the 2.1mm adapter) Cut off anything on the opposite end. © Adafruit Industries https://learn.adafruit.
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Place a big piece of heatshrink onto the cable, and then two shorter and smaller pieces on each of the wires. Solder red to red and black to black, keep the heatshrink away from your soldering iron since it may shrink too fast! © Adafruit Industries https://learn.adafruit.
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After the solder cools off, pull the smaller shrink onto the wires and heatshrink them! © Adafruit Industries https://learn.adafruit.
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Then pull the big piece over everything! And heatshrink it (with a hot air gun if you have one, or carefully with a lighter if you don't). © Adafruit Industries https://learn.adafruit.
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That's it! Check with a multimeter, in the sun, to verify that you have a open circuit voltage on the plug. © Adafruit Industries https://learn.adafruit.
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Using the Charger Solar Charging Solar charging is easy, don't forget to prepare your solar panel and solder in the electrolytic capacitor beforehand! (http://adafru.it/aN8) Once you've done that, you can simply plug in the solar panel into the DC jack - look for the PWR GOOD LED to indicate that the solar panel is providing power and then plug the battery into the BATT slot in the left. Use only 3.7V/4.2V lithium ion/polymer batteries.
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panel facing direct sunlight not shaded and not behind any glass or plastic! when the battery is full, you'll see the green DONE LED light up. USB & DC Charging Of course, sometimes is just really dark out and you can't solar charger, so there's a USB port on the board as well. Use any mini-B cable to plug in and charge.
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If you need the DC power for something else, you can also connect to the DC input via the 0.1" breakout. While you can feed power into the breakout pins as well, it's not polarity protected so make sure you use a schottky diode or just be really careful. Indicator LEDs There are three status LEDs on the charger, which you'll find very handy! The red PWR LED indicates that there is good power connected to the charger.
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Load Sharing The MCP73871 chip in the usb/solar charger has a very nifty feature called 'load sharing.' Say you have an every day lipoly charger and you want to use the battery while its charging. To do this, you might connect the project directly to the battery output. This means, however, that the charger is both charging a battery and driving your project at the same time. The charger is working extra hard and the battery is being charged and discharged constantly.
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output load from the input voltage, so that you dont lose efficiency from charging/discharging the battery. When the USB/Solar charger is powered from a USB port or panel, the load current goes directly from the input voltage to the output. If the current required is higher than what the panel or USB port can provide, the current is supplemented by the lipo battery, up to 1.
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Simply remove the 10K surface mount resistor from theTHERM pads (or cut the trace going to it), and solder in a 10K NTC thermistor (http://adafru.it/372). Test out the system by trying to charge while you place the thermistor in a freezer or against some ice, as well as in a cup of > 50°C hot water. The charger should stop charging the battery. Once you are sure it is working, attach the sensing element (the epoxy bulb in this case) so it is resting against the battery.
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The current is set by 1000/RPROG Amps, where RPROG is the resistance. So for 2 Kohms, that would make it 1000/2000 = 0.5 A = 500 mA. If you want 1A, you would use a 1K ohm resistor. If you want to increase the current, you need to decrease the resistance, so you can just solder over the existing 2K. So for example, soldering another 2K resistor into RPROG will give you 1K total resistance and 1000 mA current draw. See above for a 2.2K resistor soldered for about 950mA of max current draw.
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Design Notes Is this a Max Power Point Tracker (MPPT)? This design is not a 'true' MPPT, and we did that for a reason! Max power point trackers work by 'tracking' the voltage and current curve of a solar panel so that the total Power (Voltage * Current) is maximized. This means that as the light changes, the voltage and current must be carefully tracked.
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increases the voltages stay sort of the same but the amount of current you can draw goes up! If you can keep the DC/DC converter operating on the red line, that's the maximum power. However, there are some side effects to using a MPPT design. First is that DC/DC converters are expensive, and adding a DC/DC converter to a LiPo charger chip increases the cost by 2x.
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causes them to do one of two things: rapidly turn on and off as they try to draw more current from the panel than possible and/or draw much less current than they can, to keep the voltage from collapsing Here is a diagram of a single solar cell, in various light conditions (the colored rainbow lines): We find these diagrams common but a bit confusing. So we'll show how to use them. Pick the top red line (maximum light) and start at the very right of the line where it meats the horizontal scale.
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(the short circuit current is bigger) but the voltage of the cell is fixed at 0.5V open circuit it's just part the physics of the cell. However, you can connect a bunch of cells in series to add them up. A 6V panel has 12 cells (12 * 0.5V = 6V) Now you can see what happens if you connect a 6V solar panel to a lipoly charger. As long as the current being drawn by the charger is less than the panel's short circuit current at that light condition, everything is peachy.
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the CHRG light is on but really its doing a poor job of it! Solar Optimization! OK so how do we fix this problem? The issue we have here is that the voltage collapses during high current draw. We need to find a way to keep the lipo charger from drawing too much current, and backing off when the voltage starts to droop. We looked high and low and finally found a chip that has something like this built in.
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This schottky diode charges a 4700uF capacitor from the panel - the diode prevents the capacitor from draining back into the panel. © Adafruit Industries https://learn.adafruit.
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Downloads Files MCP73871 datasheet (http://adafru.it/aMO) Fritzing object in Adafruit Fritzing library (http://adafru.it/aP3) EagleCAD Board / Layout & Schematic files on Github (http://adafru.it/aMP) Schematic & Fabrication Print © Adafruit Industries https://learn.adafruit.