Charging Alkaline Batteries

Charging alkaline batteries is not recommended

Last updated: June 2012

Charging alkaline batteries is not recommended, even with so-called "rechargeable" alkalines in a special alkaline charger.  That's because:

1. Charged alkalines give very few recharge cycles.  You'll get only a couple dozen of recharge cycles, maybe less.  A true rechargeable like an NiMH can be recharged hundreds or even thousands of times.
2. Alkalines lose capacity every charge cycle.  That is, after every time you charge them, you get less and less run time.
3. Alkalines require constant topping-up.  You can run a NiMh or NiCd all the way without worry.  But if you drain alkalines too far then their cycle life plummets.  (Cycle life is the number of times a battery can be charged before it won't charge any more.)  So to get the best cycle life out of alkalines, you have to constantly top them up, which is a real pain.
   
4. Alkalines designed to be rechargeable often have a much smaller capacity than real alkalines—or even NiMH rechargeables!
   
5. Charged alkalines are much more likely to leak, either inside the charger, or later inside your device.  I hope it wasn't an expensive device.
6. There is not much good reason to charge alkalines in the first place.  You want to recharge your batteries?  Use NiMH.  You need more shelf-life than a standard NiMH?  Use low-self-discharge NiMH.  You need more voltage than NiMH?  Use NiZn.

I can think of only one good reason to charge alkalines:  You have a stockpile of them, or easy access to them.  (For example, I have a friend who works in a hospital which throws out tons of old alkalines, that he's able to score for free.)  He won't get many cycles out of these free batteries, but hey, they're free.

Use a special charger

If you insist on charging your alkalines, you absolutely have to use a special charger.  You can't use a NiMH, NiZn, or NiCd charger.  It must be designed specifically to handle alkalines.  There are only a few such chargers in existence.  I cover most of them below.

Chargers that purport to charge standard alkaline batteries

Some alkalines are designed to be recharged with a special charger, but some chargers purport to let you charge even standard alkaline batteries.  I think that charging either kind of alkaline is usually a mistake, but trying to charge standard alkalines is a bigger mistake.  They yield even fewer recharge cycles, the voltage drops on each cycle, and I suspect that they're even more susceptible to leaking than rechargeable alkalines (though those leak too).

Note that high-drain alkalines designed for things like digital cameras are especially resistant to charging.

Sierra Electric JB5411

I list this one first because as I write this in June 2012, it's the only battery charger still on the market that purports to charge standard alkalines.

Not that it's any better than the ones listed below.  The reviews on Amazon are simply devastating.  'nuff said.

Battery Xtender

The Battery Xtender is absolute crap.  It purports to be an all-in-one charger, charging both rechargeable and nonrechargeable batteries.  So I first tested a AAA NiMH and it didn't even fill it one-third of the way full!  So I ran some tests to see how much runtime I could get out of AAA batteries after charging them with the Battery Xtender vs. a real charger, and my results are shown at right.  Each battery was tested at least three times in each charger.

In 19% of my tests, the runtime on a battery charged with the Battery Xtender was less than one minute! The battery ran out almost immediately. But even if you tossed out all those cases, the average runtime from the Battery Manager is still woefully low, typically less than an hour.

As for alkalines, it has the same problem as all other alkaline chargers:  very few recharge cycles, decreasing capacity every cycle, and a high probability of leaking.  The table at right shows that over five years, you could easily spend more than four times as much by charging alkalines as you would by simply using real rechargeable batteries in the first place.  And if you typically burn through a set of batteries faster than once every three weeks, the penalty for trying to charge alkalines is even greater.

Five-year cost of charging a pair of NiMH vs. Alkaline (AA size) Assumes you go through a set of AA's every three weeks.
	NiMH	Alkaline
Charged with...	A real charger, like any of the ones mentioned above	Battery Xtender
Cost per set of batteries	$12.63 inc. shipping from Thomas Distributing	$1.89
Sets of batteries used in five years	1	29
Cost over five years	$12.63	$54.81
Assumptions: Two batteries per set.  Calculation for the Aklalines:  Run down most of the way before charging, so 12 charge cycles and a 200% increase in battery life.  Use of 1 fresh set every 3 weeks, or 52w x 5y ÷ 3w =86.7 fresh sets over 5 years.  86.7 fresh sets ÷ 3x increase from charging means 28.9 sets used.

But it's not just that it's a waste of money, it's a waste of time.  With the BatteryXtender you have to keep screwing around buying more batteries, AND you have to constantly keep them topped off, rather than just letting them run down like you would with NiMH's.

The user's manual says as much.  When you run down the battery most of the way before recharging you get only 12 charge cycles, and only a 200% increase in overall battery life. That means that if you got an hour's worth of run time without recharging, then with recharging you'll get three hours overall. Why wouldn't it be 12 hours if you're recharging 12 times?  Because you have to charge before the battery has run down, and because after every charge cycle the battery capacity is less than it was before.  So after screwing around with 12 charges you've only tripled your run time.

Of course, you can recharge after just a little bit of use, and thus get more charge cycles.  If you let the battery run down just a little bit before charging, then the manual claims you can get 180 charge cycles.  Except that that represents only 16x total run time compared to a single battery.  Which would you rather do to get 16x the run time of an original battery: charge a NiMH 16 times or charge an alkaline 180 times?

The sad thing is, if this charger simply charged NiMH's properly then it would be a great charger, because then it could handle everything. You could use it to charge the NiMH's you should be using, and you could use it to charge the odd alkaline you have lying around so they don't go to waste.  But since it charges a NiMH less than 1/3 full, and since there's no point in charging alkalines when you can get better performance and convenience out of NiMH's, there is really little use for this charger.

Innovations Battery Manager

This is the worst charger I've ever tested.  It purports to charge alkalines as well as rechargeables.  In fact, the alkalines I charged with it frequently leaked, either inside the charger or after they've been removed.  But that's not the worst part, since the spill in the charger can mostly be cleaned with rubbing alcohol and a cotton swab (unless the batteries leaked in whatever device they were powering, ruining it).  No, the worst parts are (1) It often refuses to charge NiCads (while these NiCads charge fine in any of the four other chargers I own), and (2) it can't even fill up a standard NiCad D battery! I'm not talking high-capacity D, I mean not even a normal D!  And the insiduous thing is, you'd never know!  I used this charger for a couple of years before I tested it and found out it had been short-changing me on the charge the whole time.  Maybe the warning sign is that this unit is sold by Real Goods, who were fairly notorious for putting misleading descriptions in their catalog (or for selling crap that just doesn't work right).  Someday I may put their laughable responses to these problems on this website.  In the meantime, here's a review from another user who hated his Battery Manager.

Buddy L Super Charger / Emerson EBR444

The Buddy L Super Charger was released in 1993 and didn't last long. (All About Batteries)  Popular Mechanics tested it and found that the first charge didn't revive alkalines back to their original 1.5V, but rather only 1.38V.  The second charge was worse—only 1.3V.  And it gets worse from there.  From the pictures I've seen, the Emerson EBR444 was the same unit with a different name.  I bought an EBR444 around 2000 and originally gave it a poor review here, but a reader pointed out how I goofed in my testing.  Doesn't really matter, since it's not easily available anyway, and even if it were, there's little point in charging alkalines, since you can only charge them a dozen or so times (if you're lucky), vs. hundreds or thousands of times for a real rechargeable like a NiCad or NiMH.  Also, this unit doesn't recharge NiMH batteries at all, a pretty serious drawback.

Homegrown alkaline battery charger

For the daring, here's one guy's plans for how to make your own alkaline battery charger.  Definitely not recommended by me.

So-called "Rechargeable Alkalines"

Even alkalines that are designed to be recharged have the same problems as standard alkalines:  few recharge cycles, decreasing capacity each cycle, and susceptibility to leaking.  So why did anyone even bother trying to make rechargeable alkalines?

The answer is that we didn't use to have good choices for rechargeable batteries.  Until the early 2000s, your only choice for a rechargeable AA or AAA battery was a NiCd, which had very low capacity.  They ran out so quickly that they almost weren't worth using.  They also had low shelf life and low output voltage (think dimmer flashlights).

Years ago I bought one of these to test.  When I get around to it, I'll post the photo of the horrible mess it made inside the charger when one of the Renewal batteries leaked inside of it.

I have some more information about rechargeable alkalines on the Battery Types page.