Can you recharge non-rechargeable alkaline batteries?

Question

There are conflicting reports of whether it is possible to safely recharge alkaline batteries (not lithium) that are not sold as rechargable. The packaging for batteries regularly has cautions against recharging. However, there are also claims that they can be successfully recharged (e.g. Ref, Ref, Ref).

One of the recharger manufacturers claims:

Our Alkaline battery charger will recharge standard alkaline batteries up to 20 times depending the type and quality of batteries used.

It is unclear whether the battery manufacturers claims are just trying to sell more batteries. Can single-use, alkaline batteries be safely and successfully recharged in standard battery chargers?

Answer 1

So far, this appears to be a Yes, provided one has the right tools.

I was first going to look at the chemistry involved, but figured it would be easier to just look at one of the top hits for chargers claiming to do this and examine its patent.

One such device is the Battery Xtender.

I searched for patents containing "alkaline battery recharger" and came across a few. I wanted to try to figure out which one was responsible for the "patented technology" claim in the link above. I simply searched the applicant's name and "battery xtender" and got it on the first hit: JD Pfeiffer of Quebec, Canada, owns the trademark to Battery Xtender, and his patent application was granted under US Patent #5,543,702 (LINK).

You can read the patent, which contains circuit diagrams and descriptions of preferred current supplies and test methods to determine when charging is completed.

Now... does it work? I can't be sure without testing one, but one of the requirements for a granted US Patent is utility -- it has to be useful (LINK). A charger that doens't charge is not useful. Assuming the US Patent Office is doing their job, the data provided by the applicant with the application showed that this device was useful!

You do have to jump through some hoops for this -- charging alkaline batteries requires that they not be depleted. Here's a page from their manual (LINK):

So, note that instead of using an alkaline battery until it's dead, one would cut it off about about ¹/₅ to ¹/₆ of it's normal life and recharge it. I don't know how long it takes to recharge, but this might amount to having an extra set or two of batteries if one is to keep cycling like this.

Wiki has an article HERE about this which references pulsed current for charging; the whole article is quite vague and un-referenced, though. I didn't see anything about pulsing in my read of the Pfeiffer patent.

So, with the right type of charger, one does appear to be able to recharge alkaline batteries intended for single use if recharged frequently and before draining very much.

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I wish there were more available test data from this device from external users/organizations. So far, nothing like that. Here's the best I was able to find. Perhaps some independent, controlled tests/reviews will come about down the road.

Answer 2

It cannot be done safely, or with more than limited success. Your results may vary.

First, we need to understand how batteries work. Two chemicals with opposite charges are separated in a cell. When a circuit is completed from the cathode (+) to the anode (-), electromagnetism happens and the two chemicals react with each other, releasing electricity, until they are in equilibrium and the battery is dead.

In order to recharge a battery, an opposite electric charge needs to be applied to the battery in attempt to reverse the reaction and restore the two chemicals to their original state. However, this is not possible with all materials. The professor states that...

nonrechargeable, or primary, batteries can be based on irreversible chemical changes. For example, the carbon-fluoride-lithium primary batteries often used in cameras generate energy by converting (CF)n and Li metal to carbon and LiF. But the starting material at the battery's cathode, (CF)n, is not reformed when a reverse potential is applied. Instead the cell electrolyte decomposes, and eventually the fluoride is oxidized to form fluorine gas.

The professor goes on to say that...

A reversible chemical change is not the only requirement for rechargeable batteries, however. To be classified as rechargeable, the battery must be able to undergo the reverse reaction efficiently, so that hundreds or even thousands of recharging cycles are possible. In addition, there must often be provisions to ensure that the recharging process can occur safely.

(emphasis mine)

In reference to alkaline batteries specifically...

The alkaline batteries (which are generally based on the conversion of MnO2 and Zn to Mn3O4 and ZnO) offer an excellent example of this last point. Although the chemical changes at the electrodes can be reversed, until recently alkaline batteries were manufactured only to function as primary cells. Recharging one of these primary cells could allow the battery to be reused, but the possible number of recharging cycles for such a cell is very limited--it performs more poorly with each recharge. More important, recharging an old-fashioned alkaline battery is not safe. During or after a recharge, the battery might generate enough hydrogen gas to cause an explosion.

This is why there are so few products available on the market, and why the ones that do exist often get poor ratings due to battery leakage (see the comments). While the chemical reaction can technically be reversed, the basic construction of a cheap, single-use battery does not provide for handling of any hydrogen buildup (which causes leaks) or protection against the degradation of the cell's contents (which limits their rechargeability).