HP Forum Archive 14

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HP-67 batteries Message #1 Posted by Miki Mihajlovic on 4 May 2004, 5:48 p.m. Would an HP-67 work on alkaline batteries of any kind or are the rechargeables a must? 1234

Re: HP-67 batteries Message #2 Posted by Jeff on 5 May 2004, 7:30 a.m., in response to message #1 by Miki Mihajlovic From an electrical perspective, I believe the general consensus is that there would be no problems with using three 1.5 Volt alkaline batteries to power a 67. The 4.5 Volt output of the three batteries is basically the same as the charger/AC adapter puts out. from a practical perspective, it may be a bit tricky to use alkaline cells. The battery pack does not really lend itself to having such cells installed and uninstalled. You could use an external pack with wire leads clipped to the battery terminals, just make sure to get the polarity correct.

Re: HP-67 batteries Message #3 Posted by Tom (UK) on 5 May 2004, 12:55 p.m., in response to message #2 by Jeff If you are worried about 4.5V being more than the 3.6V then put a diode in series with the batteries as this will drop the voltage by about 0.7V (for a silicon diode). You must use a high capacity diode (5A safe?) for driving the peak load when the card read motor is on. Please note that this will not stop you connecting the battery the wrong way round (unless you solder it to the calculator) as the diode doesn't know what lead you just connected the battery to! Perhaps you could make up a battery pack with a diode and some flying leads ending in small crocodile clips - suitably marked so you get the polarity right!

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