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How do you make rechargeable batteries last longer?

Bird's eye view of lots of batteries

Store them in your fridge or freezer. Don’t let them run down to empty. Whatever you do, don’t overcharge them. These are just some of the tips I’ve heard to make my rechargeable batteries last longer.

It’s no wonder we look for ways to eke as much life out of them as we can – given how expensive rechargeables can be. A pack of four AAs can cost between £6 and £13  – and a charger brings the bill closer to £30.

What do you do to try to make your batteries last longer?

Problems with rechargeable batteries

Manufacturers now claim that you’ll get hundreds of recharges from their batteries. The longest claim I’ve come across is the five-year lifetime guarantee or three hundred recharges (whichever comes sooner) for Duracell’s Recharge Ultra batteries.

But even with so many potential repeat uses, more than four in 10 of the Which? members we asked had problems with theirs in the past year alone.

Older batteries lasting less time between charges than newer ones, difficulties in charging them and batteries not lasting as long as expected on one use were among the most common problems.

So if you’re looking to buy new batteries. what should you look for? Our tests have found that the best rechargeables strike a balance between long battery life on a single charge and reasonably fast recharging. Plus, they don’t leak away charge when not in use.

Oh and that tip about sticking the batteries in the fridge? Our sister publication in the US, Consumer Reports, has tried this with disposables but sadly found it made minimal difference to battery life.

Can you recycle rechargeable batteries?

When they do reach the end of their useful life, rechargeables should be recycled, like disposables, at battery recycling points. You can usually find one at supermarkets or anywhere that sells a range of batteries.

A true reusable would be made from recycled material. Energizer’s EcoAdvanced range claims it’s the first disposable battery partly made from recycled batteries. It’s just 4% recycled at the moment, but the company aims to make this 40% in a decade.

What do you do to get the most from your rechargeable batteries? Have you tried any of the tips we mentioned earlier?

What problems have you had with rechargeable batteries?

Batteries not lasting as long as expected between charges (31%, 249 Votes)

Older batteries not lasting as long between charges (30%, 246 Votes)

Failing to charge altogether (12%, 94 Votes)

I have had no problem with them (8%, 62 Votes)

Difficulty charging (7%, 56 Votes)

Leakage (7%, 53 Votes)

Batteries not fitting the charger or device properly (5%, 43 Votes)

Other problems (please state in comments section below) (1%, 8 Votes)

Total Voters: 431

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Comments
Profile photo of banjo
Member

My pet hate is the AA and AAA batteries that are physically bigger in diameter than “normal” batteries and simply don’t fit torches, remotes, carbon monoxide detectors, etc. They all seem to fit chargers which tend to have springloaded contacts and spacious slots. The Lidl and Aldi brands are like that. They work really well IF you can get the battery into the device.

Profile photo of wavechange
Member

For years I used rechargeable AA and AAA cells regularly but many products (e.g. cameras) come with batteries or the drain is so low (LED torches, clocks, remote controls) that it isn’t worth using rechargeables. From limited experience of modern rechargeables, they do seem to be much better at holding their charge when not in use.

Lithium rechargeable batteries (standard in phones and laptops) can be discharged fully without harm. Other rechargeables including the types shown in the photo and battery packs for power tools should NOT be fully discharged, and you should stop using them as soon as they appear to be running out of power. What happens is that when one cell in a battery is exhausted it is reverse-charged by the others, causing further deterioration.

Some chargers are better than others. If batteries become hot when on charge they will gradually dry out and become useless.

Profile photo of Sarah Ingrams
Member

Thanks for your comment wavechange. You can indeed use devices such as phones and laptops containing lithium rechargeable batteries until they stop working and then recharge them without damaging the batteries.

With NiMH (nickel metal hydride) batteries – such as most AA and AAA rechargeables but also found in some devices such as handheld vacuums and power tools – you should recharge them as soon as you notice the performance of the device is dropping off. This will help preserve the cells in the long run.

Member
Gerard Phelan says:
29 July 2015

I have an ‘intelligent’ charger which has problems with some Maplin NiMh rechargeable batteries of C or D sizes. Even when they were just a few months old, the charger would report them as ‘bad’. A multimeter showed was probably the result of them discharging to to zero volts. So I have to start them off in an older unintelligent charger after which the ‘intelligent’ one is happy to complete the charging. ( The ‘intelligence’ is in stopping the charging when it is complete. )

Another problem I have is with older NiCad cells which I have in groups of 4 or 6 in some equipment. Now many years old, one of the set has completely failed leaving me with an incomplete set of 3 or 5 cells that are otherwise still usable. NiCad cells longer seem to be available and we are warned not to mix NiCad and say NiMh cells. It seems a waste to have to throw good cells away and C and D sized cells are expensive, whatever the technology.

Profile photo of Sarah Ingrams
Member

Thanks for your comment Gerard. I’d be interested to know the types of devices you’re using your C and D size rechargeable batteries in which seem to discharge them completely.

You’re correct that NiCad batteries are no longer available. Nickel Cadmium cells (those containing more than 0.002% of cadmium by weight) can’t be sold in the UK for consumer use, following EU legislation in 2006. Although there are a couple of exceptions – including those sold in cordless power tools (until Jan 2017) and batteries intended only for medical equipment.

Profile photo of wavechange
Member

Gerard – I have also seen rechargeable batteries that refused to charge on a modern charger. You may well be right about the reason. I have disposed of all my old rechargeables recently – they were all over ten years old. They have served me well but new ones seem so much better.

Mixing rechargeable batteries is not a good idea because this increases the likelihood that one will discharge before others and be reverse-charged, as I have described above.

The only benefit of NiCD batteries over NiMH is that they hold their charge longer when not in use. Newer NiMH seem much better in this respect.

Profile photo of wavechange
Member

Sarah – What Gerard says is quite correct. The capacity of individual batteries in an apparently identical set will differ and this difference becomes greater with age. As the batteries are discharged, one or more can become exhausted while others are still partially charged.

Member
Gerard Phelan says:
29 July 2015

The completely discharged cells are in a Grundig Concert Boy radio, that requires six type D batteries and a Yamaha electronic keyboard that requires six type C batteries. I do not use either very much, but that was why I decided to put in rechargeable batteries. There was formerly a Sony Radio Cassette player used daily that required 6 C rechargeable cells, but when the cassette part died, so did my use.
I think they expire through self discharge more than through usage. These issues have put me off extending my use of rechargeable batteries. Out of over 140 items using 254 batteries I have 6 items using 28 rechargeable standard cells, although built-in and special batteries takes my rechargeable item count to 23.

Profile photo of wavechange
Member

Self-discharge is a problem with NiCd cells and even more so with NiMH cells, at least the early ones. Rechargeable batteries are at their best if in regular use, which can save spending a fortune on disposables. I used to use rechargeables in infrequently used equipment and I became fed-up because it did not work when needed.

Profile photo of Sarah Ingrams
Member

Rechargeable cells ‘leaking away’ their charge when not in use is something we test. The worst AA culprit we’ve found lost 38% of its charge after 50 days unused – very frustrating if you want to be prepared and charge cells in advance.

Profile photo of wavechange
Member

Thanks for this Conversation and feedback, Sarah. The Which? report gives a nice example of a brand where different types of rechargeable cells lose their charge much faster than others. Years ago, I discovered this with Energizer rechargeables. I had one set that was good at retaining charge but the three sets I bought on the strength of this were hopeless.

If I can offer a tip, it’s a good idea to keep sets of rechargeable cells together, either with small coloured stickers or simply marking them with a permanent marker.

Profile photo of tomfoxe
Member

Appliances that draw higher currents use up a lot of batteries, but cheaper rechargeables have a much lower capacity than “throwaway ” types. You CAN recharge alkaline batteries e.g. Duracell but you need a dedicated charger, a standard battery charger for Nimh cells won’t work, or even a made-up charger with a higher voltage DC output. I have been recharginf alkalines with success for over 10 years, but you need to charge them before they get too flat. I test C and D cells by connecting a 1.5V/0.25A bulb and measuring the voltage when the battery is delivering current – you can’t use a voltmeter to measure the coindition of a battery that is not delivering current. If the on-load voltage is between 1.00 and 1.2 volts I recharge up to 1.45 volts. If the voltage is less than 1.00V the battery will not take a charge. If you don’;t have a voltmeter you can still do this check. If the bulb is bright the battery is good. If the bulb glows ornage/yellow rather than white, recharge. If the bulb doesn’t light, the battery is past recharging, recycle it.
If you find it’s unsatisfactory putting batteries into a keyboard or other portable appliance, you might consider using a small sla (sealed lead-acid) or other battery type. Many keyboards use a 12 volt mains adapter and 12 volt SLAs are the most common so they are relatively cheap. of course you need a charher, and making up a lead with a fuse and connector may not be your idea of making things easy. They also make rechargeable battery packs with adjustable outputs, so people can recharge mobile phones etc when they are not near a mains socket or a car. This might be an answer to your appliance battery.
Another problem is that people tend to forget how old their batteries are, and they mix old and new batteries, which reduces the overall capacity. It helps to replace them all at regular intervals, maybe every 5 years. Batteries last longer if they are newer and in similar condition, and it’s best to buy batteries of the same make and model.

Profile photo of wavechange
Member

Tom – Your post reminds me that I used to recharge alkaline cells for my heavily used Sinclair Cambridge calculator back in 1973. Like other calculators at the time, it had a LED display and exhausted a set of four AAA cells within hours. As you say, you have to recharge them before they are flat, but the capacity decreases with every recharge. Eventually I gave up, built a stabilised power supply and used that until I bought a rechargeable calculator a couple of years later. Nowadays I would not bother recharging alkaline cells, preferring to use rechargeables for heavy drain use and non-rechargeables for applications where they will last months.

I keep a 1.5 bulb handy too, but it’s more useful to check the current output on a meter. I use the 10 amp range of a digital meter to check AA and AAA. The peak current and how fast it falls within a few seconds gives a good indication of the condition. It’s not a short circuit because of the resistance of the meter. Unfortunately there is no quick test of the rate at which individual cells self-discharge.

I don’t see the point of a battery operated keyboard if it sits on the desk all day and I know several people who have swapped them for conventional keyboards. On the other hand, a wireless mouse is well worth having.

Profile photo of Joel
Member

Hi Wavechange

Thanks for your post, can you explain in a bit more detail your approach to checking current. I diligently check disposables and rechargeables to make sure their voltage is high enough but my son is always complaining that they don’t work for very long in his Xbox controller. I wondered if this was a ‘current’ issue but my physics education has a gap in this area (or maybe it is just the passage of time).

Profile photo of wavechange
Member

Hi Joel – Using disposables in gadgets that eat batteries, a voltage test is probably enough, providing that you don’t mix types or old with new.

With rechargeables, one cell may start to fail before the others, and checking the current can help to identify weak cells. With AA rechargeables, use a digital multimeter on the 10A DC range and measure the current available from each cell. It’s often necessary to plug the red lead into a different socket to use the 10A range. After charging, measure the current over a few seconds, testing each cell separately. It’s normal for it to fall but look for cells that are obviously weaker than others. Unfortunately, weak cells will only get worse even if the others are in good condition.

Profile photo of Joel
Member

Thanks wavechange. The levels danced around for the few seconds rather than fall but there was a big difference between the four, otherwise identical, just charged batteries: 2.3, 3.0, 4.0 and 5.8. I wasn’t sure which to keep using and which to recycle so I have bought a battery tester online.

For those who want to use a multimeter, and have electrical bits kicking about, then this is a good video: https://www.youtube.com/watch?v=HcikzMG7mMU

Profile photo of wavechange
Member

Lithium rechargeable batteries have been a great step forward for laptops, phones, cameras and power tools. Unlike NiCd and NiMH batteries their self-discharge is low.

The problem with making a lithium AA cell, for example, is that the terminal voltage is about 3V, thanks to the battery chemistry, compared with 1.5V for alkaline cells. There are 1.5V lithium AA cells now available and I presume these incorporate a DC to DC converter to drop the voltage.

I wonder if Which? has tested 1.5V lithium rechargeable batteries.

Profile photo of Sarah Ingrams
Member

Which? hasn’t tested 1.5V lithium rechargeable batteries as we’ve come across very limited numbers of them so far. Have you tried them? I’d be interested to hear what you think if so.

Profile photo of wavechange
Member

Having looked at this further, you are right and they are not widely available.

I have a Pure radio. The original NiMH rechargeable battery pack was hopeless but the replacement lithium one (a direct replacement) is far superior. That’s a battery pack rather than individual cells but it has made me interested in lithium rechargeable AA cells. I think I will wait until they appear in the shops rather than taking the risk because a special charger may be needed.

Profile photo of xopher
Member

The voltage of a lithium battery depends on the chemistry used. A 1.5 volt cell does not need a built in DC to DC converter. Interesting information about lithium battery technology can be found here, at:
https://en.m.wikipedia.org/wiki/Lithium_battery

Profile photo of wavechange
Member

Very interesting indeed. Thanks Xopher. I could not understand how a subminiature voltage converter could possibly handle the necessary current.

Member
bill barr says:
1 August 2015

I have a problem with the rechargeable battery on my Flymo strimmer, where the “power” of the motor falls so much that it wont cut the grass yet the green light stays on the charger showing that it is not recharging because the battery charge is not low enough. Husqvarna’s response to my complaint was to refer me to my nearest dealer where they sold me a new battery. At £50+ a time it is an expensive way to keep the lawn in order!

Member
Nicholas says:
1 August 2015

I use my camera intermittently and some batteries lose their charge between sessions. More recent ones seem to be improving

Member
Den says:
1 August 2015

I have been successfully checking and repairing defective rechargeable cordless drill batteries which, when bought new, are very expensive. When the drill only turns slowly after a recharge there is nearly always just one, or possibly more, faulty cells responsible. It’s easy to find which ones are defective by using a multimeter, preferably the old fashioned moving coil type. Unscrew the battery case to expose the individual cells, switch the meter to its10 A range and briefly connect it across each cell in turn. An instantaneous reading of approximately 4 A for say 10 seconds is normal. Any cells which do not deliver this magnitude of current can easily be detected and removed. You are simply looking for a cell or cells which behave differently to the others. New individual cells can be obtained from online dealers, or much more cheaply by splitting open used drill battery packs bought from car boot sales. Before connection, an individual cell can be tested beforehand by applying the output of a car battery charger across it and letting a current of approximately 4 A flow for about 20 s. The previous meter test should then indicate a maximum current of approximately 4 A falling slowly during a time of about 10 s. Individual cells in battery packs are spot welded but the links can easily be cut using scissors and connections made using a heavy duty soldering iron.
As new replacement battery packs usually start at around £100 it’s worthwhile attempting a repair if only one or two cells are defective.

Hope this helps!

Member
retiredsmiler says:
7 August 2015

Hi I’ve several times considered replacing defective cells in “bundled” battery packs, but have stopped short of soldering in replacements because of my concern at heating the battery by using a heavy duty soldering iron and the risk of chemical reaction and explosion. Is my concern founded?

Member

I have never found any problems with safety affecting a cell using a heavy duty soldering iron when connecting replacement cells into a battery pack. The problem, is anything, is maintaining good thermal contact and ensuring all surfaces are clean during the soldering process..

Profile photo of wavechange
Member

Individual NiMH and NiCd cells can be discharged before soldering and then the only danger is that the local heating could cause damage. It’s obviously best to solder onto the interconnecting strips of metal in the battery to be repaired where this is possible, otherwise use a powerful soldering iron and make connections as soon as possible.

I now use power tools with lithium batteries and they are brilliant compared with the old ones with NiMH and NiCd batteries, certainly for lightweight and infrequent use.

Member
Adopado says:
1 August 2015

I have NiCd batteries in AA, C and D sizes that are still good after more than 30 years! I have found that modern intelligent chargers are sometimes reluctant to initiate the charging process but my old chargers still work just fine with them.

Profile photo of Sarah Ingrams
Member

That’s impressive battery life Adopado! Do you have any tips about looking after them you can share/

Member
John says:
2 August 2015

A 9 volt 6LR battery exploded during re-charging sending the two “carbon?” cylindrical cores about two metres in opposite directions. A dent in the dressing table and the wardrobe doors covered in gunk was the result. Pretty un-nerving, especially when your bending over the charger at the time.

Profile photo of wavechange
Member

This is a useful reminder that incorrect charging of batteries can cause an explosion, though leakage or irreversible damage are more common problems. It is important not to mix different types of batteries and to use the correct charger. It is normal for batteries to become warm during charging but if they get hot, switch off immediately and let them cool before handling them.

Member
B. Doherty says:
2 August 2015

Small 9v PP3 batteries fail to reach more than a minimal/medium charge even after an extended period eg. 24hrs. Also find they are not suitable for Smoke Alarms where they do not last a long as standard batteries before needing a recharge, but also causing malfunction of the alarm and not giving the low-battery alert signal.

Nickel-Cadmium (Ni-Cad) batteries are not as good overall as Nickel-Metal Hydride (Ni-MH).

Profile photo of Sarah Ingrams
Member

Thanks for your comment B. Doherty. That’s frustrating that your 9V cells aren’t charging effectively. Do you know if they are old batteries and if they have charged fully in the past?

Some smoke alarm manufacturers recommend that you don’t use rechargeable batteries in their detectors for the reasons that you mention. Rechargeable NiMH batteries discharge in a different manner to disposables; rechargeables can start with a slightly lower voltage initially but maintain the same output fairly constantly while they’re in use, before suddenly dying when they’ve run out of charge. This can mean that the low battery warning in the detector is powered for a short time and you may miss it.

Profile photo of wavechange
Member

It is generally recommended that rechargeable batteries are not used in smoke alarms.

Profile photo of wavechange
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Sorry Sarah. I’m duplicating what you have already said. 🙁

Profile photo of Patrick Taylor
Member

A very thorough look at NiMh batteries is availlable at the respected Windows Secrets site. Proper use can extend battery life by a huge multiple so is worth reading.

A small excerpt:
” And when recharging, make sure your charger doesn’t make the battery become hot to the touch — a hot battery is a sign the charger is pumping too much current, too fast, through the battery.

Overcharging is more likely with chargers that are cheap, off-brand models; that use fast-charge circuitry; or that are wireless (inductive).

A cheap, generic charger could be little more than a transformer in a case with some connecting wires. These “dumb” chargers simply pump out current, accepting little or no feedback from the device being charged. Overheating and overvoltages can easily occur, damaging or even destroying the battery.

Fast chargers are designed to provide a useful charge to a drained battery in minutes rather than hours. There are various approaches to fast-charging technology, and not all of them are compatible with all lithium batteries. Unless the charger and the lithium battery are specifically designed to work together, fast charging could cause overheating and overvoltages. Generally, it’s best not to use one brand of fast charger on a different brand’s device.

Wireless (inductive) chargers use a special charging mat or surface to restore a battery’s power. It sounds wonderfully convenient, but inductive charging always generates excess heat, even when it’s working normally. (Some hi-tech kitchen stove tops actually use induction to heat pots and pans.)

Not only is the excessive heat produced by a wireless charger not good for lithium batteries, it also wastes energy. By its nature, inductive charging’s efficiency is always going to be significantly lower than a standard charger’s. To me, higher heat and less efficiency easily outweigh convenience. You might feel differently.

In any case, the safest approach is to use only chargers sold by the OEM of your lithium-powered device. It’s the only way to be sure that the charger will keep temperatures and voltages within specs.

If an OEM charger isn’t available, use a low-output charger that’s unlikely to pump damaging amounts of power into the device you’re charging.

One source of low-output, non-OEM charging that’s often available is the USB port on a standard PC. A typical USB 2.0 port provides 500mA (.5 amps) per port; USB 3.0 provides up to 900mA (.9 amps) per port. In contrast, some dedicated chargers will output 3,000-4,000mA (3-4 amps). The low amperages offered by USB ports will usually provide cool, safe charging of almost any Li-ion device.”

You will note the comment on charging mats – shame this information was not included in the Which? Conversation on them.

Profile photo of Sarah Ingrams
Member

Thanks for sharing so much information dieseltaylor.

to clarify, wireless chargers are suitable for lithium-ion batteries, but not AA and AAA NiMH cells. The conversation on wireless smartphone charging can be found here: https://conversation.which.co.uk/technology/wireless-charging-smartphones-worth-the-hype/