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Make External Battery for the 95LX

Make External Battery for the 95LX

I have fallen in love with my HP 95LX, even though I have barely scratched the surface of its capabilities. It has already replaced my wrist watch, my Day-Timer, my address/phone book, a scratch pad, and (with Gene Dorr's CMCALC.EXM (ON DISK ICON)), my programmer's calculator.

However, the battery life is finite, and using an AC adapter is not always convenient. I got the idea to make a small external battery pack. HP Customer Support representative, Michael Johnstone, informed me that the DC power requirement for the 95LX was +/-7.8V minimum, +/-9V nominal, and +/-12 V (175 mA) maximum.

This is ideal for using "square" 9 volt alkaline batteries, and the ability to use voltage of either polarity is wonderful for those of us who are not electrical engineers.

For just a few dollars, I obtained at a local Radio Shack (they are most everywhere) a small plastic box, four 9V battery snap connectors, a little wire, four spring metal 9V battery holders, and a coax-type barrel plug.

Using cyanoacrylate glue ("Super Glue" or "Krazy Glue"), affix the holders to the bottom of the box. One could screw down the battery holders, of course, but cementing them in makes for a neater appearance. Cut a personally convenient length of 24-gauge or better double stranded insulated wire. With a hot nail or drill, poke a whole in one end of the box. I used a nail heated over a gas range to poke the hole because I didn't have a drill, and because melting leaves the hole with smooth edges, which will not fray the wire insulation.

Solder the leads from the snap connectors, IN PARALLEL, to one set of ends of the double wire. Some "clear" silicone rubber sealant works well to insulate the soldered connections. Solder the other ends of the double wire to the coax plug. Use a little more silicone there to avoid any shorting and screw the plug back together. Be sure to put the wire THROUGH the hole in the plastic box BEFORE soldering the leads to one end and the barrel plug to the other! I didn't the first time and had to do it over.

PRESTO! You have a small external battery pack which should power the 95LX for a long time when AC isn't convenient. (I haven't gone long enough to see how long it will last, and I suppose I will have to use a cheap voltmeter to see how the batteries do.) I'm not even particularly handy with a soldering pencil, but I managed. (The toughest part was finding a glue which would fasten the battery holders to the inside of the box, because I didn't want to use screws.)

Paul O. Bartlett

CompuServe ID: [76625,150]

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