The consensus has long been against recharging normal alkaline primary AA and AAA batteries. LSD NiMHs have good cycle life, capacity, and price. And given how inexpensive an alkaline is and how quickly the capacity degrades with charging, the reward seems to not really be worth the risks of leaks or other problems.
But LSD D NiMHs are >$5 each, and they’re only 2/3 the capacity one would expect from scaling up NiMH AAs. Good alkalines are >$1. And I’ve wondered whether some things are less likely to go wrong with a D battery, especially if the charge current to capacity ratio is lower.
One downside compared to messing with recharging AAs is that if something does go wrong there’s six times the material and energy ready to be involved in the accident.
There are plenty of places where people talk about their experience recharging primary alkaline AA and AAAs, but I’ve never seen tests etc specific to larger alkalines. Anyone here know more?
In piles of disused gear I found my old Rayovac universal charger (‘Renewal’ rechargeable alkalines, NiMH, NiCad). I never bought their ‘Renewal’ batteries and only used it for NiMH; it didn’t do a great job with termination, so once I got a better NiMH charger, this started collecting dust. But it does have the advantage of fitting Cs and Ds, and maybe it’s more appropriate for this task. Old docs say it does ~500mA via pulsed charging at 50% duty cycle. That’s high enough to worry about whether it’ll make disposable AAs and AAAs leak, but maybe it’s safer with Cs and Ds. For their own rechargeable alkalines, they suggested it’d take 12 hours for Cs and 24 hours for Ds.
I’ve tried alkaline chargers in the deep past. I got 2 or 3 cycles out of them before they leaked.
Remember in an alkaline battery, the zinc metal outside shell is part of the chemistry, and gets eaten away with each battery cycle. Or so I was told. Any chemists in the audience who can verify why alkalines leak so commonly?
I don’t see much of a reason to mess with charging alkalines – much too likely to leak, you need a special charger and you get very little capacity.
If you don’t want to spring for NiMH C/D cells, there is always the option of eneloops in adapters or even 18650, 21700 or 26650 Li-ion cells in adapters (which work great in 2 or 3 C/D cell lights).
I’ve only 2 devices which use D cells, I’ve a bunch of those ubiquitous off-white coloured, plastic 3*AA to D cell converters. Loaded with 3*2400mAh cells gives 7.2Ah at 1.2V, plenty for my needs.
As an added bonus, if I don’t need full capacity, just one AA in the holder is much lighter weight!
in a life or death situation you can recharge alkaleakers.
the risk of leakage goes up about 10x
i noticed the higher frequency of leakage coincided with removal of hg from the zinc.
the supposed high purity zinc sometimes wasnt so good.
might be the problem today.
in the past i used a half wave supply with a leakage resistance across the diode to charge them.
this worked ok but the results after the first 2 cycles fell off a cliff.
nowadays its not worth it.
alkaleakers in general are a waste of resources.
I’ve given up on non-rechargable AA and AAA batteries. I’ve had too many of them leak in flashlights, remotes, radios, clocks, etc. It seems the non-alkaline “heavy duty” AA and AAA batteries are better at not leaking, but they can leak too.
I’ve switched to all rechargeables. Even using cheapo rechargeables seem to be safer than putting in “quality” alkaline batteries.