Which lead is positive ?

[bshoring]

Before investing in a charger, I want to hook up this HP35 to 3 AAA batteries to see if it works. Can anyone tell me which lead in the battery comp I should connect the positive current to? The one above the serial number or the one below? See photo.

[Massimo Gnerucci]

(11-01-2015 12:12 AM)bshoring Wrote:  Before investing in a charger, I want to hook up this HP35 to 3 AAA batteries to see if it works. Can anyone tell me which lead in the battery comp I should connect the positive current to? The one above the serial number or the one below? See photo.

You can find the answer just around the corner... ;)



(http://www.hpmuseum.org/batts/bccls.jpg)

[bshoring]

Thanks, Massimo!

[Kinma]

(11-01-2015 12:12 AM)bshoring Wrote:  I want to hook up this HP35 to 3 AAA batteries to see if it works.

Use depleted AAA batteries.
The original cells for the HP35 were 3 times 1.2 volts.
New AAA batteries produce 1.5 volts.

[Katie Wasserman]

(11-01-2015 08:02 AM)Kinma Wrote:  Use depleted AAA batteries.
The original cells for the HP35 were 3 times 1.2 volts.
New AAA batteries produce 1.5 volts.

1.2 volts is just the "nominal" ni-cad voltage, fully charged they are at 1.45 volts. 3 x AAA alkalines or primary lithium cells works great. I use this in the the HP 'Classic' series calculators I have and never had an issue.

[Harald]

(11-01-2015 03:49 PM)Katie Wasserman Wrote:  

(11-01-2015 08:02 AM)Kinma Wrote:  Use depleted AAA batteries.
The original cells for the HP35 were 3 times 1.2 volts.
New AAA batteries produce 1.5 volts.

1.2 volts is just the "nominal" ni-cad voltage, fully charged they are at 1.45 volts. 3 x AAA alkalines or primary lithium cells works great. I use this in the the HP 'Classic' series calculators I have and never had an issue.

Why not AA? I don't se any reason to use AAA. But I agree there is no problem with the higher voltage of the Alkalines.

[bshoring]

Thank you all for the great advice. My HP-35 tests just fine. Special thanks to Katie and Harald for putting my mind at ease regarding the voltage from 3 alkaline batteries.

[Katie Wasserman]

(11-01-2015 06:50 PM)Harald Wrote:  Why not AA? I don't se any reason to use AAA. But I agree there is no problem with the higher voltage of the Alkalines.

You could but if you're using alkaline cells how would you connect them up? There's not enough room in the battery compartment for springs, you can't/shouldn't solder to them, so you'd have to weld them together somehow. If you use AAA cells a 3 x AAA plastic battery holder will fit in the battery compartment very nicely and they're very easy to replace. Also, AAA alkaline cells have more capacity than the original AA nicad cells so the calculator will run for a longer time between battery replacements (or recharging as you could use AAA rechargeable cells too).

The OP didn't actually specify alkaline cells I was just assuming that.

[bshoring]

(11-02-2015 07:49 AM)Katie Wasserman Wrote:  

(11-01-2015 06:50 PM)Harald Wrote:  Why not AA? I don't se any reason to use AAA. But I agree there is no problem with the higher voltage of the Alkalines.

You could but if you're using alkaline cells how would you connect them up? There's not enough room in the battery compartment for springs, you can't/shouldn't solder to them, so you'd have to weld them together somehow. If you use AAA cells a 3 x AAA plastic battery holder will fit in the battery compartment very nicely and they're very easy to replace. Also, AAA alkaline cells have more capacity than the original AA nicad cells so the calculator will run for a longer time between battery replacements (or recharging as you could use AAA rechargeable cells too).

The OP didn't actually specify alkaline cells I was just assuming that.

Katie, What type of holder do you put your AAA alkaline cells in? I'm very interested in this approach.

Thanks!