Rechargeable alkaline battery

Rechargeable alkaline battery
Rechargeable Alkaline AA battery
Self-discharge rate	<1%/month at 20 °C^[1]^[2]
Cycle durability	25 cycles (deep), 500+ shallow^[3]^[2]
Nominal cell voltage	1.5 V

A rechargeable alkaline battery, also known as alkaline rechargeable or rechargeable alkaline manganese (RAM), is a type of alkaline battery that is capable of recharging for repeated use. The formats include AAA, AA, C, D, and snap-on 9-volt batteries. Rechargeable alkaline batteries are manufactured fully charged and have the ability to hold their charge for years, longer than nickel-cadmium and nickel-metal hydride batteries, which self-discharge.^[4] Rechargeable alkaline batteries can have a high recharging efficiency and have less environmental impact than disposable cells.

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I am your host, Doctor Krankenstein. Today we are going to find out, if in fact, it is possible to recharge a standard alkaline disposable battery, or is it a work of fiction? What says you Morby? What? Sorry, I was sleeping. Imbecile! I am attempting to bestow important scientific knowledge upon you and all of my future minions. And all you want to do is sit there and slumber? Sorry. Uh. What are you going to do with that knife? I'm going to open this parcel. I have purchased this item from a secret company known only as ebay. Oh God. And today we will determine if, in fact, this device which claims to recharge standard alkaline batteries is a miracle device or a piece of cheap Chinese junk! Well, it is made in China. So, I have devised a brilliant scientific method for testing this. First, I will measure the voltage of some brand new batteries and place them in a standard incandescent flashlight. I will then monitor the flashlight and every 30 minutes I will check the voltage again and make note of the results using a power but little known software I found called Microsoft Excel. I will keep testing until the flashlight goes completely dead. At this point I will place the batteries in the device and recharge them. I will draw a line on the batteries representing a recharge cycle. Then I will test the batteries again. I will make Morby responsible for watching the light. Jerk! After all, he has nothing better to do. The test is complete! I know the answer! OK, I'll bite. What did you find out? Well, my brainy friend! In my control test using brand-new batteries, the flashlight remained illuminated for approximately 5 hours. However, at two and a half hours, the flashlight became dim, but it continued to operate for an additional 2.5 hours. OK, and after the recharge? So, after the first recharge cycle, the flashlight operated for approximately 1.25 hours. But it only showed about 20 minutes of actual bright, usable light. And after the second recharge cycle, the results were even worse. So I can only conclude that this device is junk. So it does, in fact, recharge batteries, however if 20% of regained capacity is the best it can do, then it really does serve no purpose. We must destroy it. But wait, maybe you should try another test? What?! You DARE question my scientific methodology? NO, of course not! The testing was good. But maybe we should see how it performs under a different circumstance. You were treating the battery like a disposable battery and not like a rechargeable battery. Maybe you should not cycle the battery until it is completely dead? Hmmm.. You make a convincing point. In fact, had I been using this flashlight to see in the dark, I would have replaced the battery at the 2.5 hour mark anyway because it was so dim. Very well, I shall perform the test again, and this time I will recharge the battery at the 2.5 hour mark. Oh, we're back! So, how did the test go this time? Well, in our standard control test, the batteries were drained until the light became dim and the voltage dropped below 1.25 volts per cell. This gave us about 2.5 hours of bright, usable light. After recharging I was able to get another hour or bright light before it became dim again. So, by doing a more shallow cycle of the battery you were able to reclaim about 40% of its original capacity. Which begs the question, would it be even more successful if you cycle the battery even less? But who, upon who, would remember to recharge their batteries when they aren't dead? Nobody, that's who! I declare this product to be useless junk! Any questions before we close the show, Morby? Yes, actually. I appreciate that we're close and all. But, uh, do you have to take me into the bathroom with you? I mean, thank god I don't have a nose, but it's still awful in there! What, you jibbering lunatic! I've no idea what you're talking about. Anyway, thank you for watching the show and I bid you farewell!

History

The first generation rechargeable alkaline batteries were introduced by Union Carbide and Mallory in the early 1970s.^[3]^[5] Several patents were introduced after Union Carbide's product discontinuation and eventually, in 1986, Battery Technologies Inc of Canada was founded to commercially develop a 2nd generation product based on those patents, under the trademark "RAM". Their first product to be licensed out and sold commercially was to Rayovac under the trademark "Renewal".^[6] The next year, "Pure Energy" batteries were released by Pure Energy. After the Renewals were reformulated to be mercury-free in 1995, subsequent licensed RAM alkalines were mercury-free and included ALCAVA, AccuCell, Grandcell and EnviroCell.^[3] Subsequent patent and advancements in technology have been introduced.

Construction of rechargeable cells

Rechargeable alkaline cells are constructed very similarly to disposable alkaline cells. A cathode paste is pressed into a steel can that forms the positive terminal of the battery. The negative electrode consists of zinc powder suspended in a gel, with a steel nail contact that runs to the base of the cell to form the negative terminal. Features of the rechargeable alkaline that differ from a disposable alkaline cell include:

The presence of barium sulfate or other additives in the cathode mix, which improve cycling and increase capacity by preventing the formation of insoluble manganese compounds.
The cathode also has a catalyst to recombine any hydrogen that forms; hydrogen is produced as the fine zinc grains created during recharge are corroded by the electrolyte.
Zinc oxide is added to the cathode mix to reduce generation of hydrogen gas; the zinc oxide dissociates on charge to form oxygen.
The separator between anode and cathode is formulated to be particularly resistant to growth of zinc grains, which could penetrate and short-circuit the cell.^[4]

The cells are manufactured in the charged state, ready to use.

Charge behavior

Although these batteries can be used in any device that supports a standard size (AA, AAA, C, D, etc.), they are formulated to last longest in periodical use items. This type of battery is better suited for use in low-drain devices such as remote controls or for devices that are used periodically such as flashlights, television remote control handsets, portable radios, etc. If they are discharged by less than 25%, they can be recharged for hundreds of cycles to about 1.42 V. If they are discharged by less than 50%, they can be almost fully recharged for a few dozen cycles, to about 1.32 V. After a deep discharge, they can be brought to their original high-capacity charge only after a few charge-discharge cycles.

Recharging of disposable alkalines

Manufacturers do not support recharging of disposable alkaline batteries, and warn that it may be dangerous.^[7] Despite this advice, alkaline batteries have been recharged, and chargers have been available.^[8]^[9] The capacity of a recharged alkaline battery declines with number of recharges, until it becomes unusable after typically about ten cycles. Low-ripple direct current is not suitable for charging disposable alkaline batteries; more suitable is a current pulsed at a rate of 40 to 200 pulses per second, with an 80% duty cycle. Pulsed charging appears to reduce the risk of electrolyte—usually potassium hydroxide (KOH)—leakage. The charging current must be low to prevent rapid production of gases that can rupture the cell. Cells that have leaked electrolyte are unsafe and unsuitable for reuse. Fully discharged cells recharge less successfully than only partly depleted cells, particularly if they have been stored in a discharged state—battery charger manufacturers do not claim to recharge dead cells.^[9]

Attempting to recharge a discharged alkaline battery can cause the production of gas within the sealed canister; pressure generated by rapid accumulation of gas can open the pressure-relief seal and cause leakage of electrolyte. Potassium hydroxide in the electrolyte is corrosive and may cause injury and damage.

As an alkaline battery is discharged, chemicals inside the battery react to create an electric current. As the chemicals are used up and the products of the reaction accumulate, eventually the battery is no longer able to deliver adequate current, and the battery is depleted. By driving a current through the battery in the reverse direction, the equilibrium can be shifted back towards the original reactants. Different batteries rely on different chemical reactions. Some reactions are readily reversible, some are not. The reactions used in most alkaline batteries fall into the latter category. In particular, the metallic zinc generated by driving a reverse current through the cell will generally not return to its original location in the cell, and may form crystals that damage the separator layer between battery anode and electrolyte.^{[citation needed]}

Comparison to other rechargeable batteries

The rechargeable alkaline battery was, at one time, cheaper than other rechargeable types.^[4] Cells can be manufactured in the fully charged state and retain capacity well. Their capacity is about 2/3 that of primary cells. They are of dry-cell construction, completely sealed and not requiring maintenance. Cells have a limited cycle life, which is affected by deep discharge; the first cycle gives the greatest capacity, and if deeply discharged a cell may provide only 20 cycles. The available energy on each cycle decreases. Like primary alkaline cells, they have a relatively high internal resistance, making them unsuitable for high discharge current (for example, discharging their full capacity in one hour).

Unlike rechargeable alkaline batteries, NiMH batteries can endure anywhere from a few hundred to a thousand (or more) deep discharge cycles, resulting in a long useful life; their limitation is now more usually by age rather than cycles.^[10] Capacity of NiMH batteries is close to that of alkaline batteries.^[10] Unlike all alkaline batteries (rechargeable or otherwise), internal resistance is low. This makes them well suited for high current capacity applications.^[10] Self-discharge rates are comparable, at least up to six months.^[10]

Rechargeable alkaline batteries produce a voltage of about 1.5V, compared with NiCd and NiMH batteries which produce about 1.2V. For some applications, this can make a significant difference. In cases where resistance is not strongly dependent on voltage or current, since power varies as the square of voltage, rechargeable alkaline batteries provide about 50% more power. For example, incandescent lamps are much brighter when powered by rechargeable alkaline than by NiCd or NiMH batteries.

Environmental notes

Rechargeable alkaline batteries are developed from primary alkaline batteries, designed to resist leakage that a recharge could cause, so they can be safely recharged many times.

According to the websites of EnviroCell,^[11] PureEnergy and old Rayovac packaging, these manufacturers' rechargeable alkaline batteries have no mercury or cadmium.

References

^ "Rechargeable Batteries — compared and explained in detail". Retrieved 2016-02-28.
^ ^a ^b "Data Sheet of Pure Energy XL Rechargeable Alkaline Cells, AAA" (PDF). Retrieved 2016-03-01. (AA cell)
^ ^a ^b ^c Daniel-Ivad, J.; Kordesch, K. (3 April 2002). "Rechargeable Alkaline Manganese Technology: Past-Present-Future" (PDF). Electrochemical Society. Retrieved 28 August 2020.
^ ^a ^b ^c David Linden, Thomas Reddy (ed.), "Handbook of Batteries Third Edition", McGraw Hill, 2002 ISBN 0-07-135978-8 chapter 36 Rechargeable zinc/alkaline/manganese dioxide batteries
^ C. R. Lewart (Autumn–Winter 1975). "Supercharger" (PDF). World Radio History / Electronics Hobbyist: 46. Retrieved 28 August 2020.
^ "Reusable Alkaline Battery From Rayovac (2007)" (PDF). Archived from the original (PDF) on August 31, 2017. Retrieved May 11, 2022.
^ Duracell disposable alkaline cells are marked "Do not charge ... Battery may explode or leak."
^ "Battery Wizard". Gizoo. Archived from the original on April 29, 2014. Retrieved May 11, 2022.
^ ^a ^b It was tested by discharging batteries until completely dead, and recharging them successfully, to a lower capacity than the original capacity, a few times. Other chargers warn that they "will revive partially discharged batteries", but "will not restore completely dead" ones.
^ ^a ^b ^c ^d "Nickel Metal Hydride" (PDF). Energizer Battery Manufacturing Inc.
^ "Envirocell Alkaline Rechargeable Batteries". Envirocell. Archived from the original on February 25, 2010. Retrieved May 11, 2022.

External links

v t e Electrochemical cells
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Other cell	Atomic battery Fuel cell Solar cell
Cell parts	Anode Binder Catalyst Cathode Electrode Electrolyte Half-cell Ions Salt bridge Semipermeable membrane

This page was last edited on 1 March 2024, at 09:28

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