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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 – Zach Saucier Dec 26 '14 at 23:02
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    You need more info in order to be less specific? =p – James Webster Dec 26 '14 at 23:06
  • What information would you need? – James Webster Dec 26 '14 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... – Zach Saucier Dec 26 '14 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). – Ilmari Karonen Dec 27 '14 at 15:20
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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.

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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? – James Webster Jan 8 '15 at 19:58
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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

  • 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. – James Webster Dec 25 '18 at 20:37
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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 '14 at 0:24
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    @darthnesscoveredthesky I edited some stuff in, but this trick is just from experience. – michaelpri Dec 27 '14 at 0:28
  • 1+ I think, but you should say that the "method has been safe for me", since you cannot bring proof. Just my 2pence, though :) – Pobrecita Dec 27 '14 at 0:41
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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 '14 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 '14 at 14:36
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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. – James Webster Dec 29 '14 at 8:58
  • @JamesWebster Yes I have tested with nail. It works. But I cannot speak how safe that is for battery and users. – Joachin Joseph Dec 29 '14 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 '14 at 20:26

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