Turns out I've been recharging these alkalines for a couple years

Couple years ago got a set of holiday puck lights at Home Depot. For some reason I presumed the Defiant AAAs that came with them were rechargable. After all, thats what one uses in flashlights, right ?

So I have recharged them very frequently during two holiday seasons & not used them otherwise. Out of 24 I have tossed about half, and will toss another 6 when the are drained since they got REALLY hot on the last charge cycle. Have 5 more that didn't get hot, maybe 3 in a light still... the charger thinks they are NiMh, and it charges actual NiMh to 1.5x volts.

Yes I have bought Eneloops.

Hmmm.......what charger are you using?

I used to recharge alkalines, mostly to experiment. Be aware that there is a huge risk of them leaking, within a couple of weeks after you charge them. Don't leave them in your flashlight, unless you like cleaning up leaked batteries.

prof student said:

Hmmm.......what charger are you using?

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Gyrfalcon, holds 8 w separate circuits.

WalkIntoTheLight said:

I used to recharge alkalines, mostly to experiment. Be aware that there is a huge risk of them leaking, within a couple of weeks after you charge them. Don't leave them in your flashlight, unless you like cleaning up leaked batteries.

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Me too
back in the 80`s there was a circuit in a popular electronics mag that allowed you to recharge regular batts up about 10x before they got a bit flakey, it used something called Periodic Current Reversal. it`s interesting to note also that the batts we use here have "Do not recharge" on them and yet the same batts we send for export don`t say that! and in Japan you can actually buy chargers for regular batteries like it`s the most normal thing in the world to do! LOL
The circuit was really simple too, it was an AC current passed through a diode (making pulsed DC) and the diode had a resistor across it at 10% of the forwards charging current, so you get 100% forwards and 10% reverse, apparently it`s to stop the plating from getting spongey and remaking a smooth clean electrode surface.
from a Chemistry perspective there`s absolutely nothing in the world stopping you from doing this either, it`s just the actual mechanics of the battery itself that could create problems.

Katherine Alicia said:

The circuit was really simple too, it was an AC current passed through a diode (making pulsed DC) and the diode had a resistor across it at 10% of the forwards charging current, so you get 100% forwards and 10% reverse, apparently it`s to stop the plating from getting spongey and remaking a smooth clean electrode surface.

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I have a charger that does that. It does an okay job with alkalines (it's meant for rechargeable alkalines), but seems to stop the charge too early. I find a regular slow charger at around 150mA works better, you just have to estimate when to stop the charge. Both result in a lot of leaks within the next few days, though.

I`v yet to try the "trick" of drilling a tiny hole in a dead/ used up NiMH putting some water in and soldering the hole back up. I`v read that it does work but my jury`s still out on that one

Katherine Alicia said:

I`v yet to try the "trick" of drilling a tiny hole in a dead/ used up NiMH putting some water in and soldering the hole back up. I`v read that it does work but my jury`s still out on that one

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Well, give it a try and let us know. I expect it will turn a dead battery into a dead battery with a hole.

WalkIntoTheLight said:

Well, give it a try and let us know. I expect it will turn a dead battery into a dead battery with a hole.

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I look after my battts too well, I have no dead ones yet but I strongly suspect you`re right.

Katherine Alicia said:

I`v yet to try the "trick" of drilling a tiny hole in a dead/ used up NiMH putting some water in and soldering the hole back up. I`v read that it does work but my jury`s still out on that one

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To my recollection that was a trick for reviving carbon-zinc dry cells where the paste had dried out.
In the construction of zinc can <-> paste <-> center carbon rod <-> sealant over the paste,
sometimes the sealant was poor and pulled away from the zinc can walls leaving cracks, letting the moist paste dry out.

When I was a kid (~60 year ago) No. 6 ignition cells were a common power source for hobbyists. When they were depleted, I would sometimes drill a hole in the top and add water -- actually I think I added salt water. I believe I did this to many cells, so it must have appeared to work.

Hand-cranked telephones were still being used (my maternal grandparents in rural New York State had one in the 1950s) with No. 6 cells to either enable or improve service. I suspect folks developed strategies to keep them functioning as long as possible.

I have a couple of chargers which claim to recharge regular alkalines, have used them with
limited success. Recovered capacity is nowhere close to original, and they sometimes leak
even during charging. I believe the process works best on cells which are not too heavily run
down.

Limited use as I am busy running down everyone else's primary alkalines, see thread:

https://www.candlepowerforums.com/vb/showthread.php?473112-reclaiming-alkaline-(and-other)-cells

In the 1990's I experimented with rechargeable alkalines (Pure Energy and Ray-O-Vac). Cells
had lower peak current capability, initially had a fraction of capacity of regular alkalines and lost capacity
fairly early in their life, and overall didn't seem to live up to the 20-30 cycles claimed. Besides
this, they also leaked. I have a couple of chargers for these which also do NiMH at a slow rate,
which is good for older cells which often are not charged by fast-chargers (rapidly blinking light).

Dave