HP 15c Limited Edition OLD batteries

[ytterligare]

WAS : "Really disappointed by HP : 15c Limited Edition"

I know, I read elsewhere people are having problem with this calc's keyboard.

I'm not, or at least I don't think it is the keyboard.
I purchased this calc brand new in 2011, used it for maximun 10-20 hours, then stored it away in a dry place ( home ).
Reopened the box today, I started to use it for fun, and this happened :

https://youtu.be/iX1fBrKA1pA

Now, the batteries seem to be in good shape ( they both measure 2.9 V ), I've tried either the "ON+"-" reset method, the paperclip on the back and shorting the battery terminal , but nothing seems to help : after the "Pr Error", which sometimes is "corrupted", the behaviour is the same.
I'm really disappointed, since the calc is technically almost brand new....anyone any idea ?

Tnx
A.

[jebem]

Imho the batteries at 2.9V may already be depleted, as they have high internal resistance and when complex current load is imposed by the calculator processor (this model has nothing in common with the origin high quality high impedance low leakage current 15C) it is expected to see the voltage dropping below the value you reported (assuming you measured the cells with no load).

Basically I would use fresh good quality batteries to test the calculator.

[ytterligare]

(11-19-2020 04:01 PM)jebem Wrote:  Basically I would use fresh good quality batteries to test the calculator.

Good point your reasoning : I will buy a fresh new set and report.
After all, the batteries might be 10 years old if not more......

Tnx
A.

[grsbanks]

Make sure you get batteries of a reputed brand. Those cheap no-name Chinese batteries have many problems, among which an inordinately high internal resistance and poor capacity.

[ytterligare]

(11-19-2020 07:05 PM)grsbanks Wrote:  Make sure you get batteries of a reputed brand. Those cheap no-name Chinese batteries have many problems, among which an inordinately high internal resistance and poor capacity.

Yes, got 4x Energizer LiOn from Amazon, delivered tomorrow.
My guess is that those were the original one, so they might well be 10-12 years old...and chinese.. :-D

[CMarangon]

Hello!

This seems to be a problem of the keyboard blanket, that is corroded.


Keyboards usually have a "blanket" like this one in the picture, it is between the letters and the PC board and are usually affected by moisture.

Pic 01 - Keyboard and "blanket"


I was unable to find a HP15 keyboard pic,
so I posted this PC keyboard, just to see its parts.

[ytterligare]

Ok, thank you all people, fortunately, the Keyboard problem CMarangon is reporting, has not hit my 15c LE yet.

On other hand, with a new set of fresh batteries, I'm happy to announce that the 15c now works like a charm.
I was mistakenly thinking the old set was still charged, as they reported 2.9V, but as jebem pointed out, when really old, some batteries tend to suddenly drop the voltage when under load.

Now, I''ll try to change the subject of this series of post, as I was in error.

Ciao
A.

[lyuka]

It may have been caused by the "high current spike problem" of the HP15C limited edition.


HP 15C Limited edition, power supply current

[ytterligare]

(11-20-2020 04:40 PM)lyuka Wrote:  It may have been caused by the "high current spike problem" of the HP15C limited edition.


HP 15C Limited edition, power supply current

Good thought !!
To keep aside for future modding...

Thank you
A.