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My HP-15C revives......
10-04-2018, 08:10 AM
Post: #1
My HP-15C revives......
Several cases of dead HP-15C were reported such that the calculator couldn't power on after installing new batteries. My HP-15C was bought in August, 1985 and was being used quite often for 5 years and then intermittently for the remaining years. Batteries remained in the battery compartment although the low battery indicator (asterisk) was blinking. After the calculator couldn't power on, I bought new batteries and replaced them with new ones. However, it didn't power on and looked dead for two days but the new batteries still stayed in the battery compartment. I kept on pressing the ON button and other buttons one by one randomly twice a day. On the third day, 'running' suddenly popped up on its display. Yes, it revived!

I don't know how far my HP-15C can go but I'm thrilled to have it back at this instant. Have faith in your HP-15C!
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10-04-2018, 08:43 AM
Post: #2
RE: My HP-15C revives......
You might not have had to wait a couple of days if you'd removed the new batteries, shorted out the battery contacts in the 15C, pressed a few buttons for a while and re-inserted the batteries Smile
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10-04-2018, 09:16 AM
Post: #3
RE: My HP-15C revives......
(10-04-2018 08:43 AM)grsbanks Wrote:  You might not have had to wait a couple of days if you'd removed the new batteries, shorted out the battery contacts in the 15C, pressed a few buttons for a while and re-inserted the batteries Smile

I replaced batteries for so many times in the last 33 years. However, this is the first time that I encountered this situation. I once thought that some components inside the calculator might have malfunctioned considering its age.
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10-04-2018, 11:10 AM
Post: #4
RE: My HP-15C revives......
(10-04-2018 09:16 AM)Johnny Shek Wrote:  
(10-04-2018 08:43 AM)grsbanks Wrote:  You might not have had to wait a couple of days if you'd removed the new batteries, shorted out the battery contacts in the 15C, pressed a few buttons for a while and re-inserted the batteries :)

I replaced batteries for so many times in the last 33 years. However, this is the first time that I encountered this situation. I once thought that some components inside the calculator might have malfunctioned considering its age.

Some people would swear that they replaced the batteries in a voyager just once in that time frame.
:)

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10-04-2018, 12:53 PM
Post: #5
RE: My HP-15C revives......
My original 15c was bought 1988 and the first battery change was in 2003...
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10-04-2018, 02:06 PM
Post: #6
RE: My HP-15C revives......
Apart from the frequency of use, I think the battery life depends on the kind of batteries you use and the weather conditions surrounding the calculator. According to p.259 of the Owner's Handbook, you may choose between two breeds, either lithium or silver-oxide. The latter can last twice as long as the former but it seems that the latter is never available in my place. My place also has long hot and humid summer, which may shorten the battery life.

In my experience, each set of fresh batteries can last for 4 to 5 years on average.
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10-04-2018, 02:08 PM
Post: #7
RE: My HP-15C revives......
(10-04-2018 02:06 PM)Johnny Shek Wrote:  According to p.259 of the Owner's Handbook, you may choose between two breeds, either lithium or silver-oxide.

Huh?

ITYM alkaline or silver oxide... They both have a cell voltage of around 1.5V while a lithium-manganese battery is 3V.
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10-04-2018, 02:23 PM
Post: #8
RE: My HP-15C revives......
(10-04-2018 02:08 PM)grsbanks Wrote:  
(10-04-2018 02:06 PM)Johnny Shek Wrote:  According to p.259 of the Owner's Handbook, you may choose between two breeds, either lithium or silver-oxide.

Huh?

ITYM alkaline or silver oxide... They both have a cell voltage of around 1.5V while a lithium-manganese battery is 3V.

Yes, you're right! Should be alkaline.
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10-04-2018, 04:28 PM (This post was last modified: 10-04-2018 04:36 PM by Thomas Okken.)
Post: #9
RE: My HP-15C revives......
I wonder about the usage pattern of people whose Voyagers run for over decade before needing new batteries. I used to own an HP-10C in college, which I used a lot; I used it in my studies and exams, and I enjoyed the challenge of programming it, with its severe limitations (I also had a 41CX, on which, of course, everything was easy). I would run through a set of batteries in a matter of months -- and I started using even more after I had had it undergo speed-up surgery (which was slightly disappointing, I think it was about 1.6 times faster afterwards, while I had expected 2x).

I'm not complaining about several months on one set of batteries; I actually thought that was pretty good, given how heavily I used it. But how do you make a set of batteries last 10, 15, 20 or even more years?

Hmm, maybe my 10C was just out of spec? I don't have it any more, but I did buy a used 10C on eBay a while ago; I guess I could just pop a fresh set of batteries in there and set it to run a program with an endless loop, and see how long it takes before the low-battery warning comes on, and how long before it dies. If anyone has run this kind of test before, what did you find?
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10-04-2018, 05:31 PM
Post: #10
RE: My HP-15C revives......
(10-04-2018 04:28 PM)Thomas Okken Wrote:  I wonder about the usage pattern of people whose Voyagers run for over decade before needing new batteries. I used to own an HP-10C in college, which I used a lot; I used it in my studies and exams, and I enjoyed the challenge of programming it, with its severe limitations (I also had a 41CX, on which, of course, everything was easy). I would run through a set of batteries in a matter of months -- and I started using even more after I had had it undergo speed-up surgery (which was slightly disappointing, I think it was about 1.6 times faster afterwards, while I had expected 2x).

I'm not complaining about several months on one set of batteries; I actually thought that was pretty good, given how heavily I used it. But how do you make a set of batteries last 10, 15, 20 or even more years?

Hmm, maybe my 10C was just out of spec? I don't have it any more, but I did buy a used 10C on eBay a while ago; I guess I could just pop a fresh set of batteries in there and set it to run a program with an endless loop, and see how long it takes before the low-battery warning comes on, and how long before it dies. If anyone has run this kind of test before, what did you find?

I bought my HP-11C new in early 1987 and sold it around 2000. It still had the original alkaline batteries that it came with. The low battery indicator had just started to come on occasionally. I had used it heavily at my job for about a year until I bought a used HP-28C (followed by other HP models). After that I very rarely used my HP-11C.

From the HP-11C Owner's Handbook (P230):
"A set of alkaline batteries will provide at least 80 hours of continuous program running (the most power-consuming kind of calculator use). A set of three fresh silver-oxide batteries will provide at least 180 hours of continuous program running."

"If the calculator remains turned off, a set of fresh batteries will preserve the contents of Continuous Memory for as long as the batteries would last outside of the calculator - at least 1-1/2 years for alkaline batteries or at least 2 years for silver-oxide batteries."
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10-04-2018, 06:16 PM
Post: #11
RE: My HP-15C revives......
I have an HP11C which I bought as a spare in the mid 80s in case my main calculator failed (a 41cx at the time) since I have serious trouble using a standard calculator. Probably have less than 40 hours of actual use on it and it still has the original batteries in it and is running fine.
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10-04-2018, 09:59 PM
Post: #12
RE: My HP-15C revives......
So the secret of a set of batteries lasting extremely long in a Voyager is basically "don't use it"? Smile

Still, impressive that those machines manage to keep their memory powered with such a tiny standby current, which is even less than the already tiny self-discharge current! And at the same time, running down a set of batteries within months, with heavy use including much running of programs, sounds like it is well within specifications, too. Nice to know!
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10-04-2018, 11:07 PM
Post: #13
RE: My HP-15C revives......
The life of alkaline battery is very short.
Some manufactory make the voltage of alkline higher than normal to last it's life.
It may hurt some electronic device.
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