Very nice aaa battery pack for Classic Calculators

[Waterhosko]

Folks,

I've built very nice battery packs for the Classic Calculators that uses any AAA batteries. I'm offering at a discount to all HP Calculator Museum followers. I sell them for $25 + shipping on Ebay but will drop it to $18 and no shipping in USA (yet please add $12 additional international shipping). Please note attached picture.

Drop me an email waterhosko@aol.com if you'd like. Hope it's ok to send a note here?

Any tech feedback on using alkaline batteries in a generally lower voltage realm of rechargeable cells? I have not seen any problems with my calcs so far using alkaline, but I'm curious about the long-term effect of the initially higher voltage within these calculators?

Mark Hoskins

[Massimo Gnerucci]

Hi Mark, this looks like a nice solution for classics.

I already found out your pack and mentioned it here...

Do you combine shipping charges for multiple orders?

Thank you very much!

[Waterhosko]

Yes I'd be glad to reduce costs for international shipping. Also if I send the cases with no cells I can even drop shipping costs more. Say $5 shipping.

I am still curious about the voltage issue. I have a friend who heard that alkalines will ruin the calculators. He does not know for sure this is true. I have measured voltages on charged battery packs over 4 volts. So I'm not at all convinced that alkalines will hurt the calculators.

Does anyone know for sure?

I have been running my calcs: HP-45 and HP-67 with no problems, on this case with AAA alkaline cells.

[Maximilian Hohmann]

Hello!

(06-03-2016 12:42 AM)Waterhosko Wrote:  Does anyone know for sure?

No, but I would rather ask: Why use alkaline batteries in the first place?

Rechargable 2500Ah NiMH batteries cost exactly the same as good alkalines and provide the voltage the calculator was designed for. The calculators can safely be used with it's charger when working at one's desk (try that with alkalines instead...). And, also import to some, one set of NiMHs outlasts 500 sets of disposable batteries.

Regards
Max

[Dieter]

(06-03-2016 09:54 AM)Maximilian Hohmann Wrote:  Rechargable 2500Ah NiMH batteries cost exactly the same as good alkalines and provide the voltage the calculator was designed for. The calculators can safely be used with it's charger when working at one's desk (try that with alkalines instead...).

As usual, I would not recommend the highest available capacity but Panasonic Eneloop NiMHs. They feature virtually no self-discharge so that they can be used even in calculators that you use only every few months.

The higher capacity compared to batteries of the Seventies yields a much lower relative charging current. This again means, with the original charger attached, harming the batteries by overcharging is nearly impossible. #-)

(06-03-2016 09:54 AM)Maximilian Hohmann Wrote:  And, also import to some, one set of NiMHs outlasts 500 sets of disposable batteries.

With an intelligent charger offering decent charge control, that is. I would not rely on this figure when using the "dumb" original HP chargers.

Dieter

[Dieter]

(06-03-2016 12:42 AM)Waterhosko Wrote:  I am still curious about the voltage issue. I have a friend who heard that alkalines will ruin the calculators. He does not know for sure this is true. I have measured voltages on charged battery packs over 4 volts.

Near the end of the charging process NiCds and NiMHs can and will reach voltages of 1,4 V per cell and more, in some cases even beyond 1,5 V. That's close to the output of a new Alkaline battery.

(06-03-2016 12:42 AM)Waterhosko Wrote:  So I'm not at all convinced that alkalines will hurt the calculators.
Does anyone know for sure?

Noone can say this for sure unless the electronic specification of the particular calculator is known. But this topic has been discussed here several times over the years. I only remember posts that say Alkalines are fine. After all, if a new Alkaline has 1,55 V and a fully charged NiMH 1,45 V, that's merely 7% difference. But again, I do not think there can be a definitive answer, unless...

Dieter

[Leonid]

(06-03-2016 12:42 AM)Waterhosko Wrote:  I am still curious about the voltage issue. I have a friend who heard that alkalines will ruin the calculators. He does not know for sure this is true.

IMHO, even NiZn rechargeable batteries (1.65 V) can't destroy calculator although still better to use low self-discharge nickel–metal hydride batteries (LSD NiMH) like Panasonic Eneloop 2100 (4th gen) with Smart Charger.

[Sylvain Cote]

I received this morning a AAA battery holder for the Classic & 75C/D/Pod series from Mark.
I had another one that I bought years ago from another vendor but it broke into pieces on the first drop.
This one is very sturdy, well made, easy to use, fit exactly the battery space and accept regular or rechargeable AAA.
The holder came with 3 NiCad AAA already charged in it.
Regards,
Sylvain

[motjebben]

I just purchased one of Mark's AAA battery cases and LOVE it!

It is well made, fits into the classics' compartment easily, and - with NiMH batteries - allows one to recharge the batteries with a separate charger to keep the classics safe. It ticked all of my boxes for the right solution.

Mark also gave me some advice about the proper charger port pins to connect when a classic doesn't power up on batteries. I know I had seen such before, but Mark's reminder was timely, as two of mine did not initially power up. I have multiple calculators stored in climate-control (WITHOUT BATTERIES - to prevent corrosion), hence it has been awhile for some of them....

Thank you, Mark!

Kind regards,
Mike

[teenix]

(06-03-2016 12:53 PM)Dieter Wrote:  Noone can say this for sure unless the electronic specification of the particular calculator is known. But this topic has been discussed here several times over the years. I only remember posts that say Alkalines are fine. After all, if a new Alkaline has 1,55 V and a fully charged NiMH 1,45 V, that's merely 7% difference. But again, I do not think there can be a definitive answer, unless...

Dieter

Okey doke, I used a HP-45 CPU board and ran it through a range of voltages. I got to say, for such a simple switch mode supply it does pretty well.

The voltage range I used was from 3.16V to 4.5V.

VGG stays steady around -12.30V
VSS stays steady around 6.06 - 6.09V

The issue is VCC, it changed from 7.05(3.16V) to 8.3(3.75V - standard) to 9.9V (4.5V) and would go higher for higher battery voltages.

So VCC increases by 1.6V using 3 x 1.5V alkalines - theoretical 4.5V. I don't know if this puts stress on the chips, but it might do because of their age.

The other issue if the peripheral devices that run directly from the battery, coils for the LED displays, sense IC etc. These will have increased voltages but again, I can't say if they will be damaged, and I don't want to destroy a board to find out :-)

The Classic charger supplies a fixed voltage for the CPU board during charge, and the batteries are charged separately so if the charging battery voltage rises it won't affect anything, unless after charging the loaded voltage is above the normal 3.75V.

cheers

Tony