A question about alternative power supply for hp41 series

[Dieter]

(02-24-2016 06:09 PM)wojtek Wrote:  But just count, on average 1800 mAh for a single nimh accu...

What battery size do you want to use? Typical AA NiMHs have 2000...2500 mAh, some even more (well, at least the label says so), while AAAs are typically 700...800 mAh.

(02-24-2016 06:09 PM)wojtek Wrote:  ...would give 1mA for some 500 hours till the voltage drops to some 1V from 1.2V. With 100uA the accu would last for 5000 hours or 200 days.

Let's say a running HP41 draws 10 mA at 6 Volts. That's 60 mW. Even with a 100% efficient voltage converter these 60 mW would translate to 60 mA at 1 V input voltage. Using a 800 mAh NiMH battery this means 13 hours. Or roughly one sixth of what you get ouf of a set of four regular Alkaline N-cells, resp. a quarter if N-size NiMHs are used. Unrealistically assuming 100% efficiency, that is. At 25% it's only 1/4 of these figures, i.e. in total roughly 5% of an N-size battery set.

Please correct me if I'm wrong here.

Dieter

[wojtek]

Sorry, I should have been more specific here. I was talking about low discharge accus, like eneloops, which typically have about 1800 mah (although there some low discharges wchich have more than 2000 mah)
Regular nimh accus perhaps can have even 2500mah, according to their makers, but, if you leave for a month or two a fully charged low discharge (with 1800 mah capacity) and a regular accu (with 2500mah), their charge will become the same (because of much bigger discharge feature of regular accu). Later with time every low discharge will win over the regular nimh accu. After three or more months regular nimh will become completely empty but low discharge will still keep more than 80% of its initial charge.
I am using only low discharges and have at home more than 50 pieces of AA and AAA. In the long run low discharges are cheaper than any regular nimh accus.

As for the calculations in the second part of your post, I was talking about 41c in the off state only. I do not know how much juice 41c takes while running, certainly it depends on what 41c is doing. For example if you would leave 41c in endless loop it probably would empty the batteries during less than 12 hours.
I have no data on power consumption of 41c during typical average usage (but would like to know it if anybody knows where to find it.

[Artur - Brasil]

Just converting your words (I really would like to use HP50G solver):
t - time of continuous work [hours]: what we want to know
Cbat - battery capacity [mA.h]: let's say 2000mAh
Eff - converter efficiency [%]: 90%
Vbat - battery voltage [V]: 1.2V
Vcalc - operating calculator voltage: 6V
Icalc - operating calculator current [mA]: 10mA

So, using the solver for hp50g...

t[h] = Cbat*Eff.Vbat/(Vcalc.Icalc.100)

t = 36h of continue work;

Not bad, as I won't use it for so long time at once. Let's say, 1 hour daily -> easily 30 days.
Being less confident in numbers, I would say recharging battery once a week. Not bat, at all....

This if we don't put two AA batteries inside the battery holder - my mistake: really forgot to measure it yet.
And remember, we have stronger cell phone batteries available too.
   
Beyond calculations, what I really would like to express is this simple point: N cells here are difficult to find; I have some rechargeable, but thery are always depleted when I need them - and the charger is hard to find too... AA battery is easy to find (ready to use 1.5 alkaline or 1.2 NiMH, also easily chargeable).
so, its a question of hard x easy and also a new project to keep my mind occupied with something positive.

[rprosperi]

(02-25-2016 02:26 PM)Artur - Brasil Wrote:  N cells here are difficult to find

Here, Amazon has a set of 20 N Cells for less than $1.00 each, not expiring until 2019 (and they of course actually last longer). While shipping to Brazil surely adds to the cost, they are still pretty easy to buy and IMHO, pretty cheap.

[Artur - Brasil]

Actually not expensive, but, I really will try this funny project.
I consider all yours ideas and suggestions, really, but this will be my first contact with such converters and a good experience with them.

[wojtek]

(02-25-2016 03:24 PM)Artur - Brasil Wrote:  Actually not expensive, but, I really will try this funny project.
I consider all yours ideas and suggestions, really, but this will be my first contact with such converters and a good experience with them.

It is not complicated at all, at least as for the electronics. I would have made it some week ago but have a problem with that weird connector to fit into the slot on the left side of mine 41c.
Any ideas how to make it? Make a cast of epoxy resin? A mould should be made first.
I even bought a 3d pen, but it is useless for such tasks in my opinion.

[Artur - Brasil]

Hi,
I have the 41 which has already the balls connected to main board.
About the connector that come from wall power supply, it's quite simple! Do you have one usual HP power supply?
Look at its connector - it is a divided in two, ok? (my language is not helping here...).
I cut two small alluminium plates and, at one end, I folded them (as it was a pin) and insert in the hole of connector. So, I folded again and glued on the upper side of connector. These plates will make the contact to the balls.
The power supply was modified too, as I rectified and stabilized it on 6V using one simple 7806.
Very, very simple and works great!
I'll post some pictures when I get home.

[wojtek]

(02-25-2016 05:24 PM)Artur - Brasil Wrote:  Hi,
I have the 41 which has already the balls connected to main board.
About the connector that come from wall power supply, it's quite simple! Do you have one usual HP power supply?
....
I'll post some pictures when I get home.

I have the HP charger but I need it for my notebook...
Thanks for the pictures to come!

[Artur - Brasil]

No, no. The charger for HP calculators (10~12Vac).

[Dieter]

(02-25-2016 02:05 PM)wojtek Wrote:  Sorry, I should have been more specific here. I was talking about low discharge accus, like eneloops, which typically have about 1800 mah

Panasonic (or formerly Sanyo) rate their standard AA Eneloops at 2000 mAh typical capacity (1900 mAh minimum).

(02-25-2016 02:05 PM)wojtek Wrote:  Regular nimh accus perhaps can have even 2500mah, according to their makers, but, if you leave for a month or two a fully charged low discharge (with 1800 mah capacity) and a regular accu (with 2500mah), their charge will become the same (because of much bigger discharge feature of regular accu). Later with time every low discharge will win over the regular nimh accu. After three or more months regular nimh will become completely empty but low discharge will still keep more than 80% of its initial charge.

Please don't get me wrong: I am perfectly aware of the many benefits that low-self-discharge batteries like the Eneloops offer. I have recommended them several times in this forum, and I have been using them since they became available about ten years ago. Yes, of course these are the best choice here.

(02-25-2016 02:05 PM)wojtek Wrote:  As for the calculations in the second part of your post, I was talking about 41c in the off state only. I do not know how much juice 41c takes while running, certainly it depends on what 41c is doing.
(...)
I have no data on power consumption of 41c during typical average usage (but would like to know it if anybody knows where to find it.

Maybe these links can help:
Measuring Calculator Current PDF (cf. page 3)
HP41 Info data (search for "battery current")
Some more results in an older post on this forum.

Dieter

[wojtek]

(02-25-2016 08:51 PM)Dieter Wrote:  Panasonic (or formerly Sanyo) rate their standard AA Eneloops at 2000 mAh typical capacity (1900 mAh minimum).

I was buying eneloops successively a few years ago and then 1800 mah was a standard capacity.

Thank you for the links, I'll check them

[wojtek]

        I enclose a picture of mine HP41c powered by a converter 12-5.5V and single nimh AA accu. The setup is very simple and provisional for a while, the capacitor on the right side has 100uF. I do not know yet what is the power consumption and how long the accu will last. The converter used is a backup power up of a telephone and can provide some 600ma max. The nimh accu used had about 1.1V.
On the second picture the electronic circuit is shown. It is very small, about 16mm in diameter and will fit in the battery holder of 41C without problem (of course without the aluminium body shown in the picture) along with a single nimh AA accu.
Electronic setup took some 10 minutes to assemble but the problem for me was in making the connector to 41C (after a few tries I decided to make it of the epoxy resin)
But in the near future I expect even greater problem in making the cover of the battery holder of the 41C. I would be grateful for any ideas how to make it.

[rprosperi]

(02-27-2016 12:09 AM)wojtek Wrote:  I enclose a picture of mine HP41c powered by a converter 12-5.5V and single nimh AA accu.

Many of these posts refer to "accu" - is this another name for battery? Is it a slang term, or maybe a translation?

[Dieter]

(02-27-2016 01:37 AM)rprosperi Wrote:  Many of these posts refer to "accu" - is this another name for battery? Is it a slang term, or maybe a translation?

In some languages "accu" is a false friend, for instance in German. Here the term "battery" ("Batterie") usually refers to a disposable, e.g. Alkaline battery, while rechargeable batteries are called "Akkumulator", or shorter and more common, "Akku". I assume this also applies to some other languages where it may be confusing that in English both disposable and rechargeable cells are simply called "battery".

Dieter

[wojtek]

(02-27-2016 01:37 AM)rprosperi Wrote:  Many of these posts refer to "accu" - is this another name for battery? Is it a slang term, or maybe a translation?

No :-0, no slang, no translation, it was only because of my laziness, typing many times "accumulator" in a single post was tooo much for me. I hoped it should be understandable. OTOH (on the other hand :-) mine Am Heritage Dict says: "accumulator" - chiefly Brit. an automobile storage battery, and Longman dictionary says: "accumulator" - esp. BrE, a type of battery ...

[wojtek]

(02-27-2016 06:48 AM)Dieter Wrote:  In some languages "accu" is a false friend, for instance in German. Here the term "battery" ("Batterie") usually refers to a disposable, e.g. Alkaline battery, while rechargeable batteries are called "Akkumulator", or shorter and more common, "Akku". I assume this also applies to some other languages where it may be confusing that in English both disposable and rechargeable cells are simply called "battery".

Dieter

Thank you, I can remember that I met this word (accu) probably in Karl Marx "Winnetou". I had not undestood then what was its meaning, but certainly it could mean "false friend".

[wojtek]

Going back to HP41c and voltage converter.
I left 41c over the night powered by the single nimh. During 6 hours voltage dropped about 0.1V and 41c calculated more than 60000 square roots of 2. So it could give some 12-15 hours of continous work. But the nimh was the oldest I could find at home, more than 10 year old Energizer with nominal capacity of 1800 mah and real probably less than 1000mah (I was afraid of damaging any of my eneloops).
Certainly if someone would like to apply such a converter to power the 41c it would be worth to invest in the newest eneloop of 2500mah capacity

[jebem]

(02-27-2016 08:11 AM)wojtek Wrote:  

(02-27-2016 01:37 AM)rprosperi Wrote:  Many of these posts refer to "accu" - is this another name for battery? Is it a slang term, or maybe a translation?

No :-0, no slang, no translation, it was only because of my laziness, typing many times "accumulator" in a single post was tooo much for me. I hoped it should be understandable. OTOH (on the other hand :-) mine Am Heritage Dict says: "accumulator" - chiefly Brit. an automobile storage battery, and Longman dictionary says: "accumulator" - esp. BrE, a type of battery ...

In Portuguese language we commonly use the term "Acumulador" as a rechargeable battery a well.
EDIT: The same as in Spanish language.

[walter b]

(02-27-2016 08:18 AM)wojtek Wrote:  

(02-27-2016 06:48 AM)Dieter Wrote:  ... rechargeable batteries are called "Akkumulator", or shorter and more common, "Akku". I assume this also applies to some other languages where it may be confusing that in English both disposable and rechargeable cells are simply called "battery".

Thank you, I can remember that I met this word (accu) probably in Karl Marx "Winnetou". I had not undestood then what was its meaning, but certainly it could mean "false friend".

Now that's going to become a real chaos.

• A 'false friend' in linguistics is called a term in a foreign language looking similar like a term in your native language but meaning something different. Some English examples for German readers: sensitive, handy, become, etc.
• 'Winnetou' was written by Karl May, a Saxonian fake traveller.
• Karl Marx was a different guy. Based on your name, I'd guess you wouldn't have got along with that confusion some 30 years ago.
• If Karl May ever wrote something looking like 'accu' he must have meant anything in a (for him) foreign language - since the German term for a rechargeable battery is 'Akkumulator' as mentioned by Dieter above. I admit having read a lot of his books when I was a kid though don't remember that piece of text.
  

Enjoy!

d:-D

[wojtek]

(02-27-2016 09:06 AM)walter b Wrote:   Now that's going to become a real chaos.

• A 'false friend' in linguistics is called a term in a foreign language looking similar like a term in your native language but meaning something different. Some English examples for German readers: sensitive, handy, become, etc.
• 'Winnetou' was written by Karl May, a Saxonian fake traveller.
• Karl Marx was a different guy. Based on your name, I'd guess you wouldn't have got along with that confusion some 30 years ago.
• If Karl May ever wrote something looking like 'accu' he must have meant anything in a (for him) foreign language - since the German term for a rechargeable battery is 'Akkumulator' as mentioned by Dieter above. I admit having read a lot of his books when I was a kid though don't remember that piece of text.
  

Enjoy!

d:-D

Thank you for interesting grammar info. I didn't know that.
Of course I distinguish both Karls one from another. The one named Marx will become related in history forever with his boy friend Fritz Angel (just kidding)
I supposed that "accu" was used in conversation between old surehand an old firehand during their visit at fake general's hacienda, but I can be wrong.