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Cell Phones,
Telephone
Circuits,
Battery Chargers
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Do It Yourself Portable Cell Phone
Charger August 24, 2009
It seems that as cell phones become more sophisticated, their operating times become
shorter and shorter. If you are on the go all the time and have difficultly finding
AC or DC outlets to charge your phone, you might consider this simple scheme. |
| First, check to see what voltage your cell
phone requires. The AC power adapter should list its voltage and current output.
Most phones have their own internal lithium ion battery charger circuit, which accepts an
external 5 volts, from either an AC wall adapter or a special 12v DC cigarette lighter
plug. A pack of 4 NiMH AA rechargeable cells delivers very close to this voltage and
should charge nearly any cell phone battery. With quality cells rated at 2.5
amp-hours, the pack stores about 12 watt-hours of energy. This is about 4 times what
many cell phone batteries store. This allows the pack to recharge a nearly dead cell
phone battery some 3 or 4 times, extending talk time by that same factor.
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| The scheme is pretty low tech. First,
buy a covered 4 AA cell battery pack like shown below. Radio Shack and other places sell
such battery holders. Buy a pack of four 2500ma-hour NiMH cells. I have had very good
luck with the Energizer brand. Wire a coaxial power plug to the two wire leads coming
from battery pack. The red wire should be soldered to the center plug terminal.
Next, tap into the red and black wires of your AC or DC charge adapter for your phone with
two insulated wires. Your adapter might look something like the one shown
below. Solder the other end of the two wires from the phone plug to a DC power
jack, matching the plug from the battery pack. That is it. When you plug the
phone adapter into the phone and the battery pack to the power connectors, your phone
should indicate a charging mode. Disconnect the pack when the phone is fully
charged. |
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After two to four charge
cycles, the AA cells should be removed from the holder and recharged in a standard NiMH
charger as shown below. Both AC and DC charge stations are available. |
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Cell Phones,
Telephone
Circuits,
Battery Chargers
Master Category List - Dave's Circuits |
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