I have a battery charger that requires batteries are charged in pairs. However I have a wireless keyboard that uses three batteries. Is there a (safe) way I can charge all of the batteries at once?

I usually have to go through two sets before I can charge the 'lone pair', but I often misplace the one that's waiting.

If it helps, the device is a Duracell CEF14UK

enter image description here

  • Can you provide a little more info about the device? It seems a bit too specific for a lifehack to me Dec 26, 2014 at 23:02
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    You need more info in order to be less specific? =p Dec 26, 2014 at 23:06
  • What information would you need? Dec 26, 2014 at 23:06
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    You could try making a fake battery of sorts. Something that has a little weight and connects the two ends. Not sure how safe it'd be... Dec 26, 2014 at 23:18
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    Your real problem is that you've got a crappy battery charger. Get a better one -- it'll make your batteries last longer, too. Here's a rather fancy model selling for $18, but you should be able to find a perfectly good 4-channel charger for less than $10. Please do not try to "hotwire" your cheap charger to take just one battery -- you'd end up feeding it twice the usual charging voltage, which can't be good for it (and might not even be safe). Dec 27, 2014 at 15:20

8 Answers 8


I suggest rotating the batteries through the charger. If it takes two hours to get a full charge on two batteries, that would be 120 minutes. Total time to charge 3 batteries would be 50% more than that or 180 minutes. Put batteries in the charger for one-third of the 180 minutes which woulds be 60 minutes. Remove the battery from the left. Move the one from the right to the left. Move the extra one into the right position. Do that three times and the three batteries will each be charged the required amount of two hours.

  • This has one problem: it will reduce the lifespan of your batteries. The charger in question places two batteries in series. When you do that with 2 batteries that have a large difference in charge state, you end up charging one battery more than the other.
    – Hobbes
    Jan 16, 2020 at 11:17
  • When in series the one with the least charge will drop the most voltage, yes, but as it becomes charged it will drop less and less voltage until both batteries drop the same voltage when charging. Think about it and you will see that's the only way the charger will work. Jan 17, 2020 at 14:28

There's no (known) hack for this -- you should buy a better charger, that can charge any number of batteries at the same time; anything else probably isn't worth the effort, probably isn't safe, and could damage your batteries. See here and here for more info on why this is so.

I had this same problem (but with three-cell LED headlamps). Finally gave up and bought a charger (LaCrosse BC-700) that would charge 1-4 batteries - and a mix of AA and AAA cells, too. More than worth the $35-40 cost in eliminated aggravation.

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    Since there are now a few valid hack answers, is this now a bad answer? Jan 8, 2015 at 19:58
  • IKEA's STENKOL charger allows for charging 1-4 mixed batteries (AA/AAA) with mixed capacity. Each port charges separately. It is currently listed at 8$.
    – Kibsgaard
    Jul 13, 2022 at 12:00

Take a rechargeable battery out of some other device in the house, and charge it

No other rechargeables in the house? Buy or obtain (places like supermarkets have battery bins where old batteries can be put for recycling. Someone is bound to have thrown a rechargeable away by mistake) another battery. If you're good at losing batteries but good at not losing chargers, secure the battery to the charger using string and electrical tape so you have an accessible battery to make up the pair any time you need to charge an odd number of batteries

I concur with other comments on this page that you should NOT attempt to bridge the terminals of the empty slot with wire, screws etc because it's quite likely your charger is charging a pair of batteries in series and doing this would see the lone battery be destroyed as the charger will forever try to charge it to make it reach the ~2.5volts it expects a pair to be, and it'll never get that high. If this charger is charging in series pairs, charging a single battery with double the voltage could be a fire risk

I also concur with comments that you should buy a better charger that can charge an odd number of batteries/charge independently; battery charging in series works well when both cells are functional and effective but if one cell is degraded the other one suffers

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    As it turns out, this is what I did. I have two clocks that take one battery each. When one needs recharging, I charge them both. Dec 25, 2018 at 20:37
  • "battery charging in series works well when both cells are functional and effective but if one cell is degraded the other one suffers" - and yet you're recommending taking a battery from the recycling bin (where it likely ended up because it's degraded).
    – Hobbes
    Jan 16, 2020 at 11:19

First of all, do NOT just short circuit the battery charger with a piece of foil to force it to charge your battery individually. Looking at the spec sheet provided, your charger outputs 3V to each pair of batteries to charge them in series. If you place a single battery in the charger and force it to charge, then your charger will be supplying 3V to a 1.5V battery and end up destroying it.

However, you can still use this charger if you are very careful. Instead of short circuiting the other battery terminals, place a resistor in them to slow down the current. Use a 10 ohm resistor and attach it to the terminals. Then you can carefully monitor the battery as it charges to make sure it doesn't overvolt. You will need to check it frequently until it reaches capacity and then remove it before it gets destroyed.


(inspired by @subjectivist's and @caius-jard's answers)

increase your supply of rechargable batteries and rotate their usage.

e.g. with four batteries you can charge all 4 → use 3 → when they're done, you're left with 1 charged and 3 uncharged → charge 2 → 3 charged ready for use + 1 uncharged waiting for the next chance to charge → when the batteries are empty again you have 4 uncharged batteries ready to charge all 4. You might want to use a different battery to be waiting for usage so they all have similar number of duty cycles.

If I counted correctly, with 7 batteries you could even manage to have near zero down time on battery change (i.e. whenever the batteries you're currently using, there will be at least three batteries ready to use so you can just swap and continue using the keyboard.

It would probably require another life hack to keep track of which battery had the most duty cycles.


The safe bet, although a bit more expensive, is to use 6 batteries:

  • use 3, recharge 2, 1 left empty;
  • use the other 3, recharge 2, 1 left empty;
  • recharge the 1+1 left empty batteries.

This will ensure uniform proper charging / discharging cycles for all batteries.

There might me a slight concern that some batteries will stay dis-charged for some time, until the next 3 batteries get used. This should be acceptable though, as nothing in the world is perfect.

On the other hand, there are portable devices which use only one battery - hopefully you have one of those. Pair the keyboard to that device, maybe manage to have all 4 batteries discharged at (more or less) the same time.

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    Dear down-voter, will you please be brave enough and explain your down-vote? Thank you.
    – virolino
    Jan 21, 2020 at 5:39

I've never had this exact problem, but occasionally I've had to make fake batteries out of aluminum foil. This will just send the electrical signal back to the circuit and keep it running.

How to make it:

  • Use can use a battery as either a model or something to mold the aluminum foil around (I prefer the mold)
  • Just wrap the aluminum foil around the battery and it should fit in the charger

This method has been safe for me and the aluminum foil has lasted pretty long (I've had one for about 6 months). Just make sure to turn of the charger before removing the fake battery.

  • Firstly, this is really interesting :) Secondly, are there any health risk we should know of? How long can it stay, etc? Also, maybe there are some sites that might be of help with the development of this answer.
    – Pobrecita
    Dec 27, 2014 at 0:24
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    @darthnesscoveredthesky I edited some stuff in, but this trick is just from experience.
    – michaelpri
    Dec 27, 2014 at 0:28
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    I would not suggest this, as without an understanding of how the charging circuit in your specific charger works, you could have problems anywhere from a ruined battery and/or charger to a fire (not likely, but I wouldn't try this in my house). It might work, but if it doesn't, bad things could happen.
    – TomG
    Dec 28, 2014 at 19:52
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    usually with cheap Ni-Cd, Ni-Mh and rechargeable alkaline chargers (like yours) there's a power source with a resistor in series with the battery pair. The resistor's job is to limit the current to the maximum that a fully discharged battery can safely take. If you replace one battery with a short circuit you may initially get too much current for the remaining battery, but it's unlikely to be unsafe, it may however cook the battery a bit, shortening its life. For Lithium batteries however this would certainly be dangerous - they do catch fire if not charged properly.
    – stib
    Dec 29, 2014 at 14:36
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    In case any chargers use a series circuit, this would be really deleterious advice. Sep 26, 2019 at 10:16

If you have one battery less for charging to use battery pair charger, Use a metal screw as a replacement. It is a good conductor.

enter image description here

  • This is the sort of answer I was expecting, but is it safe? Have you tried it. Dec 29, 2014 at 8:58
  • @JamesWebster Yes I have tested with nail. It works. But I cannot speak how safe that is for battery and users. Dec 29, 2014 at 9:32
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    This seems like a really bad idea. It puts twice the voltage on the battery it is supposed to be recharged with. That's certainly not healthy for the battery and might even be dangerous.
    – Philipp
    Dec 29, 2014 at 20:26

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