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Old 26th Jun 2014, 11:19 pm   #1
Tractorfan
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Smile Alkaline battery charger?

Hi,
I spotted this gadget in our local supermarket a couple of months ago. Sorry the photos are fuzzy. It's a plug in battery charger that can, apparently, charge alkaline 'single use' AA, AAA & PP3 batteries which would otherwise be thrown away. Has anyone tried one of these and, if so, how effective were they? I may be wrong, but I think they use something other than just DC to charge ordinary cells. I've not seen one before and am just curious, as ever.
Cheers, Pete.
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Old 26th Jun 2014, 11:33 pm   #2
Bazz4CQJ
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Default Re: Alkaline battery charger?

I think I can hear an alarm bell. Over the years, we've probably all tried putting some energy back in to primary cells in moments of dire need. But isn't the risk that you might start generating gas and that a cell could burst with some violence?

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Old 27th Jun 2014, 12:59 am   #3
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Default Re: Alkaline battery charger?

Charging dry cells was a fairly regular feature in the electronics magazines, using unsmoothed DC with plenty of ripple. The usual advice was to do it regularly, only partially discharging them in-between.
I'm not sure the modern thin walled cells will be as successful as the older ones.
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Old 27th Jun 2014, 1:26 am   #4
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Default Re: Alkaline battery charger?

These chargers have been around for decades. They don't generally inject enough current to cause explosions but their effectiveness is very variable, depending on the battery brand and state of discharge. They can sometimes be used to extend the life of alkaline batteries used in a low drain application like a radio, but there's a lot of faffing about for a very small benefit. Low discharge NiMH batteries are available now at very low prices, so there's little point in trying to use alkalines in a manner for which they weren't intended.
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Old 27th Jun 2014, 7:58 am   #5
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Default Re: Alkaline battery charger?

They are unlikely, as said above, to cause explosions but with certain cells in particular will almost certainly provide you with a gooey corrosive mess. In my experience some makes will not accept hardly any charge at all before leaking (Duracell, Kirkland) and others (Sanyo, Fuji and old Energizer) are remarkably good. Do note though that the internal resistance of the cells does rise when you do this; for small current drains this has little effect but, for high drain applications, the cells may not perform well enough.
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Old 27th Jun 2014, 11:06 am   #6
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Default Re: Alkaline battery charger?

The only time I had an alkaline battery leak explosively was when "charging" via a charger intended for charging NiCd cells. This was many years ago, and was with some unused Duracells that I had had for some time and thought might benefit from freshening up before use. It used to work fine with the old Ever Ready Blue U2 unsealed leclanché cells which never leaked. I never had problems with part-used alkalines, other than lack of success in regaining capacity.
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Old 27th Jun 2014, 11:25 am   #7
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Default Re: Alkaline battery charger?

Quote:
Charging dry cells was a fairly regular feature in the electronics magazines, using unsmoothed DC with plenty of ripple. The usual advice was to do it regularly, only partially discharging them in-between
Quote:
These chargers have been around for decades. They don't generally inject enough current to cause explosions but their effectiveness is very variable, depending on the battery brand and state of discharge.

Tried it once on some Duracell AA's. Didn't work and they leaked all over the bench.
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Old 27th Jun 2014, 11:25 am   #8
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Default Re: Alkaline battery charger?

I experimented with this and I now won't do it.

The reason was the rather sinister problem that I found. I could charge a non-rechargeable up but that about a week or two later it would suddenly vent a load of electrolyte and gas for no obvious reason. If it failed during charging I could live with that, but the "time bomb" aspect was a guarantee to mess up equipment.
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Old 27th Jun 2014, 11:44 am   #9
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Default Re: Alkaline battery charger?

I honestly would not bother, I have tried this in the past with little success, I also ruined a charger due to the battery leaking goo into it.

Rechargeable batteries are so cheap these days, that it simply is not worth it.

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Old 27th Jun 2014, 3:43 pm   #10
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Default Re: Alkaline battery charger?

They don't actually recharge the batteries but rather depolarise them, it depends on the condition and type of battery whether this is effective or not, it worked best with the old carbon-zinc cells but even then they had to be in good mechanical condition.

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Old 27th Jun 2014, 8:01 pm   #11
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Default Re: Alkaline battery charger?

I find NiCad etc, rechargables very little use for radios, as I usually use most radios occasionally and I find they don't hold a charge for long periods. But well worth knowing that alkaline cells are likely leak if recharged. I have used such a device and found it did inject new life, although not as much as the sales blurb claimed. Good £ shop Duracells for me.
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Old 27th Jun 2014, 9:29 pm   #12
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Default Re: Alkaline battery charger?

Modern low discharge NiMH batteries retain their charge for ages if not used and you would only need to charge them every 6 months or so. They have become the dominant type on sale now, and even the ones sold in Poundland are of this type, though these have quite low capacity (800mAH for an AA). 2000mAH ones are quite widely available, and even higher capacity ones exist.

http://en.wikipedia.org/wiki/Nickel%...ischarge_cells

It's not a good idea to leave batteries of any type in a radio that's not being regularly used, as any battery technology can leak.
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Old 27th Jun 2014, 9:35 pm   #13
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Default Re: Alkaline battery charger?

It's funny. Every few years, a device claiming to do something along these lines appears for "primary" cells with all sorts of breathless claims. Then it vanishes. Until next time round.

I suspect that, every now and then, someone has a bright idea based on limited success, gets a container load made out East, gets loads of returns and complaints and opts to go out of business.
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Old 27th Jun 2014, 10:16 pm   #14
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Default Re: Alkaline battery charger?

I sense you may be correct there; some of these 'snake-oil' devices got pretty advanced though - a friend in Wakefield has one with LCD display (of voodoo Volts & capacity). Given the capacity metering on even very expensive rechargeables can be somewhat dodgy after the first year or so I don't have much confidence for that given for a 10 year old SP2 being charged for the 4th time!
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Old 8th Jul 2014, 9:02 am   #15
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Default Re: Alkaline battery charger?

Some revealing real-life tests on primary cells here. http://www.batteryshowdown.com/
Seems the most unlikely ones are better than some of the well-known brands.
I tried several different reviving techniques at one time, but none of them were worth the bother, or the messy eruptions that occurred. Tony
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