New Project Farm Battery Testing

[mfleming]

Eneloops left in a device and under light load (e.g. keeping memory contents safe) will eventually discharge and occasionally end in a reversed voltage state. The voltage dropoff is pretty steep so you may not get a low battery warning in a timely manner. I lost a 48GX when this happened, so the usual rule of removing batteries when not in daily use applies.

~Mark

[AnnoyedOne]

(12-18-2024 05:17 PM)HPing Wrote:  Our Casio electronic dictionary from 2013 has a setting that allows configuration for different types of batteries, including eneloops.

Lithium metal (non-rechargeable) batteries "die" very quickly. NiMHs also "die" quickly but less so than Lithiums. Alkalines "die" much more slowly.

Some devices contain a "battery type" setting so that the battery level indicator accounts for the above.

A1

[HPing]

(12-19-2024 01:02 PM)mfleming Wrote:  Eneloops left in a device and under light load (e.g. keeping memory contents safe) will eventually discharge and occasionally end in a reversed voltage state. The voltage dropoff is pretty steep so you may not get a low battery warning in a timely manner. I lost a 48GX when this happened, so the usual rule of removing batteries when not in daily use applies.

Did the drained eneloops destroy the 48GX or just wipe your stored items?

(12-19-2024 01:20 PM)AnnoyedOne Wrote:  Some devices contain a "battery type" setting so that the battery level indicator accounts for the above.

That is a useful feature but is a bit irritating to set every time. Indeed, the Casio electronic dictionary has a battery level indicator.

[mfleming]

(12-19-2024 05:18 PM)HPing Wrote:  

(12-19-2024 01:02 PM)mfleming Wrote:  Eneloops left in a device and under light load (e.g. keeping memory contents safe) will eventually discharge and occasionally end in a reversed voltage state. The voltage dropoff is pretty steep so you may not get a low battery warning in a timely manner. I lost a 48GX when this happened, so the usual rule of removing batteries when not in daily use applies.

Did the drained eneloops destroy the 48GX or just wipe your stored items?

Not entirely sure about the damage. The screen briefly shows some pixels when ON is pressed, then no longer responds until the batteries are removed and the contacts shorted. I would guess (hope!) damage to the power supply somewhere, but have had no time to investigate. Everything is SMT anyway, except for a couple of discrete capacitors...

Relying on another 48GX that requires pressing beneath the display to get the ON key working

[HPing]

(12-19-2024 08:17 PM)mfleming Wrote:  Not entirely sure about the damage. The screen briefly shows some pixels when ON is pressed, then no longer responds until the batteries are removed and the contacts shorted. I would guess (hope!) damage to the power supply somewhere, but have had no time to investigate.

Thanks for the insight... I'll still go with the eneloops and remove them for storage.

[Steve Simpkin]

(12-19-2024 08:17 PM)mfleming Wrote:  ...
Relying on another 48GX that requires pressing beneath the display to get the ON key working

I have one with the same issue. I used a nylon cable tie and a folded piece of cardboard to constantly apply pressure on the area under the display as a temporary fix. Here is a photo of someone else who did a cleaner job using a plastic bar under the nylon cable tie.
https://drive.google.com/file/d/12oh-Qd7...drive_link

[AnnoyedOne]

(12-19-2024 08:17 PM)mfleming Wrote:  Not entirely sure about the damage.

I cannot imagine how batteries could kill a device other that leaking corrosive chemicals over the insides. I assume that wasn't the case with the Eneloops.

My guess is a failure coincidental with the batteries going flat.

Then again knowing that the HP-25 is known to self destruct if an AC adapter is attached with a missing/dead battery pack I'm not sure.

A1

PS: I downloaded the very latest (dated 3/3/2023 & 12/12/2022) Energizer Alkaline & Lithium AA datasheets. The ones I had were "old". Anyway the Ultimate Lithium AA's now claim a shelf-life of 25 years. The MAX AA Alkalines 12 years. Not sure if better data became available or the chemical composition of the batteries changed. Either way the "discharge rate" graphs decrease almost linearly for the Alkalines and with a steep "knee" dropoff for the Lithiums. In laymans terms the latter "die" (lose capacity) very quickly. The former don't. That said the Lithiums have a much higher mAhr rating.

[bxparks]

(12-20-2024 01:29 PM)AnnoyedOne Wrote:  

(12-19-2024 08:17 PM)mfleming Wrote:  Not entirely sure about the damage.

I cannot imagine how batteries could kill a device other that leaking corrosive chemicals over the insides. I assume that wasn't the case with the Eneloops.

We had a previous discussion about this in June 2024:
https://www.hpmuseum.org/forum/thread-21...#pid188859

When multiple NiMH batteries are in series, one dies to 0V, then the other good cells can drive the dead cell into reverse polarity. I've seen that happen myself. Then the next cell dies to 0V, and gets driven to reverse polarity, and so on. Until the last good cell dies to 0V. The final state of the batteries could be that the reverse polarity cells send negative voltage into the calculator. Maybe this damages the calculator if it doesn't have reverse polarity protection? This is just speculation at this point, no experimental data. [Edit: fix grammar typos]

[AnnoyedOne]

(12-20-2024 04:15 PM)bxparks Wrote:  This is just speculation at this point, no experimental data.

You may be correct although I've never seen that myself. I have seen NiCads/NiMHs "short" internally and go to 0V. I've "recovered" some (via externally applied voltage) and others not.

Whatever the case I decided some time ago that they're not worth the cost/effort.

A1

[bxparks]

(12-20-2024 04:23 PM)AnnoyedOne Wrote:  Whatever the case I decided some time ago that they're not worth the cost/effort.

Funny. I have had so many alkaline batteries leak that I have decided the opposite: I will always use NiMH whenever possible. I will not use alkalines unless I am forced to. I will absolutely never use Duracell. Its reputation has been destroyed by its previous private equity owners, as private equity almost always do.

[Jase]

(12-20-2024 04:41 PM)bxparks Wrote:  I will absolutely never use Duracell. Its reputation has been destroyed by its previous private equity owners, as private equity almost always do.

I've had the same bad luck. A year ago, I told my wife to stop buying them, and to start buying Energizer. It's still too early to tell, but I think/hope that the Energizer will be less prone to leaking.

These days, Duracells will leak if you merely look at them funny.

[AnnoyedOne]

I just checked my records and the last time I purchased a bulk-pack of Duracell AA's was in 2014.

I don't know the details but Duracell seems to have destroyed their brand name perhaps in the pursuit of short-term profits. If so they weren't the first to do so. Nor will they be the last. Unfortunately we live in age where this happens. Pay attention and act accordingly is my advice.

As an aside I see that Panasonic now makes Eneloops. Presumably Sanyo sold the battery division to them.

I've personally been on both sides. I've worked at companies sold and others that bought others. None have worked well in the medium/long term IMO.

A1

[Steve Simpkin]

(12-20-2024 06:38 PM)AnnoyedOne Wrote:  ...
As an aside I see that Panasonic now makes Eneloops. Presumably Sanyo sold the battery division to them.
...
A1

For reference:
"In 2009, Sanyo was acquired by Panasonic, and in 2011, it was fully consolidated into Panasonic and its brand disappeared."
https://en.wikipedia.org/wiki/Sanyo

[mfleming]

(12-20-2024 04:15 PM)bxparks Wrote:  We had a previous discussion about this in June 2024:
https://www.hpmuseum.org/forum/thread-21...#pid188859

When multiple NiMH batteries are in series, one dies to 0V, then the other good cells can drive the dead cell into reverse polarity. I've seen that happen myself. Then the next cell dies to 0V, and gets driven to reverse polarity, and so on. Until the last good cell dies to 0V. The final state of the batteries could be that the reverse polarity cells send negative voltage into the calculator. Maybe this damages the calculator if it doesn't have reverse polarity protection? This is just speculation at this point, no experimental data. [Edit: fix grammar typos]

If all three Eneloops had reversed, then that could have damaged an electrolytic cap and account for the brief flash of the display before not responding further. It's been some years since opening a 48 for repair (not a pleasant experience) but a spare board does show a cap connected to the positive battery contact.

Might as well open it, nothing to lose but my temper . . .
~Mark

[AnnoyedOne]

(12-19-2024 08:17 PM)mfleming Wrote:  Everything is SMT anyway, except for a couple of discrete capacitors...

FYI I recently replaced the 20yr old coin cells in my 15C/16C calculators with new Energizer 357 silver oxide batteries.

The HP-15C gave a "Pr Error". From what I've seen from photo's both it and the 16C have a small electrolytic through-hole "discrete" capacitor that is supposed to hold the memory contents while changing the batteries. Since that didn't happen I assume that it has long since failed.

https://www.hpmuseum.org/forum/thread-22337.html

The HP-20S had "cheapie" LR44 coin cells in it.

https://www.made-in-china.com/showroom/1...ttery.html

Those are gone and replaced with Energizer 357's.

A1