June 2013
How can I make a cable so that I could use a nine volt battery for my cell phone? Would a large six volt lantern battery work? Are there any electronics needed?
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How about 6V lantern battery?
First, a 9V "transistor" battery doesn't have enough current to run a cell phone. The Lantern battery might work. Look at your cell phone battery, it will be a Li-ion probably 3.7V, so you will need to lower the voltage of the lantern battery to that.
Next, measure or just read on the battery, which pins are + and -. Then, figure out how to connect to the small pins/strips inside the phone. In one of mine, I found that using the little hook-type clips worked fine.
That should do it. If you need to learn how to make a voltage reducing circuit, I believe that both linear types, using a LM317 chip as well as some of the newer switching chips have already been published in N&V. I found the LM2575. http://pdf.datasheetcatalog.com/datasheet/SemtechCorp/mXvqxtq.pdf
First, determine how long you want the phone to run, and choose a battery with enough milliampere hours for the duration. (A 9 volt radio battery may be inadequate).
That said, for efficiency I recommend a switching converter such as the On Semi MC34063. See the datasheet for how to use. For an inexpensive inductor consider the toroidial inductor CR-345 from AllElectronics.com. This should have more than enough capacity to not run dry. If, in the future, you need a voltage inverter, be aware that I have found other datasheets to be in error with their circuit for this part, but the ON Semi circuit works well. Simply use the formulas in the datasheet. If the source voltage is close to 12 volts, than a surplus car adapter for your phone from Goodwill is the low cost option.
