I have an almost dead laptop battery and read in this forum that

"The problem with most of the broken batterys is that they are exhaustive discharged. the trick to solve this is to give them a high voltage electricity source like a laptop charger (20V). I did that to all the 3 lion batteries I found inside the macbook battery but just for a few seconds to reactivate them and now they are working fine"

I am curious whether this is theoretically possible if nothing else.

  • 5
    I have heard about this but I don't know if it was lead-acid (difficult to blow up) or NiMH/NiCD (less difficult to blow up). I wouldn't try it with Li-on or Li-Poly (too easy to blow up) – AngryEE May 25 '11 at 1:28
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    Voltages aren't passed through: currents are passed through, voltages are applied across. This is more a matter of having the concepts right in your mind than just being pedantic about the terms used. – Martin May 25 '11 at 7:49
up vote 28 down vote accepted

This is a known effect of NiCad/NiMH batteries.
Doing it to any other battery risks setting something on fire.

Basically, Nickel-metal batteries, when over-discharged, can grow little metal whiskers or "dendrites" between the internal plates, shorting the cell out. Applying a high voltage to the cell causes enough current to flow that the dendrite fuses and melts, and therefore, the cell is not longer internally shorted, and can hold a charge. (This is what the guy in avra's response was doing to the batteries)

However, letting a cell go completely flat (0V) is quite bad for it, so the battery will never completely recover. However, it may hold some charge afterwards.


Note that what the guy in the quote is doing is not applying a high voltage to the cells, but applying a high charge-current to the cells he is referring to. The laptop charger he describes is likely only good for a few amps, and the output voltage is probably dropping massively when it is connected.

The only thing I can think of is that some laptop batteries have a built-in protection system. If the battery is discharged fully, and then let sit and self-discharge for a while, the protection system may not even get enough power to turn itself on, and therefore, the laptop will not realize a battery is even present.
When he manually charges the batteries a small amount with his external adapter, by taking the battery apart, it may be just enough to activate the battery protection circuit, so it can charge normally afterwards.


Applying a significant over-voltage to ANY cell chemistries for any period of time can be dangerous.

  • On lithium cells, you will get metallic lithium plating out of the electrolyte when the cell voltage is above 4.3V. Metallic lithium can catch on fire when exposed to (the moisture in) the air.
  • In Lead-Acid batteries, you will begin to electrolyze the electrolyte, causing the battery to vent hydrogen and oxygen. This is EXTREMELY EXPLOSIVE.
  • I have read many times that when a lithium ion discharges too much it will trip the charge control circuit and it will not accept a new charge as the charge controller is no allowing current. When pulsed with a high voltage in this state a small amount of trickle allows the charge controller to reset and allow charge. I read an article saying that this makes up more then 90% of cell phone battery returns. I will try to find you links. – Kortuk May 25 '11 at 15:08
  • this seems to talk about it some. – Kortuk May 25 '11 at 15:09
  • I can confirm that "jump starting" from a bench power supply works for NiMH batteries. Here's what I have tried with AA and AAA NiMH cells: set a bench power supply to a max. current of 1 A and 0 V. Connect the battery. Increase the voltage until the current maxes out at 1 A. After a short time, the current will decrease to some mA. This is about when a normal charger will be able to charge the battery without indicating "BAD". Do this with NiMH cells for just some seconds, maybe repeat, and don't try it for batteries containing Lithium. – zebonaut May 25 '11 at 20:42
  • @Kortuk - If you are applying a high voltage to the battery IO pins, you may be doing bad things to the controller circuit, like overvoltaging the the protection switching MOSFETs. It may work, but it may damage the battery circuitry subtly. – Connor Wolf May 25 '11 at 22:50

Lithium batteries have around 1/6th the energy in them as TNT. Do not mess around with over powering the battery unless you like fires or explosions.

The method was used to clear shorting in NiCd batteries but should never be used for Lithium without understanding all the risks.

As with many of the responses, it is possible that it will do what you want. Just understand that there is a possibility of the pack exploding or burning and take precautions for that.

  • this is used in Lithium also. – Kortuk May 25 '11 at 15:10
  • @Kortuk, you are correct. I have slightly changed my answer to reflect this. I believe most of the respondents wanted to error on the side of safety, because this could be a very dangerous thing to do without full knowledge. – Joe May 25 '11 at 15:57

Messing with lithium ion (LiIon) and lithium ion polymer (LiPo) batteries is a very dangerous thing to do and will likely result in fire and flames. LiPo and LiIon fires are VERY dangerous.

enter image description here

Attempting this will probably result in catastrophe. This guy got lucky. Another guy had his house burn to the ground.

  • 1
    this resembles the outcome in the garage of the guy i knew that was rolling his own lithium packs. – JustJeff May 25 '11 at 12:07
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    Does this really answer the question? – Kellenjb May 25 '11 at 15:03
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    @Kellenjb I'm just warning the OP that messing with lithium batteries is very dangerous. – Thomas O May 25 '11 at 15:11

I don't know about theory, but in a company I worked for, we used to have hundreds of 3000$ mobile devices in use and every month we had 3-4 with a dead NiMH battery. It was strange since we knew that most batteries were quite new, and it was pretty much expensive to send them for a repair and wait for their return. Luckily we found an electrician who "repaired them" in a day very cheaply, and he mentioned using some short time high voltage shock.

If you current limit the high voltage, like a big computer grade capacitor, you can restore some batteries to life. The failure modes in rechargeable batteries are many. ( @fake guy indicated one) It is important to prevent secondary failure while healing with warped plates, thin metal film or foil or melting something other than metallic impurities and insulated crystals inside the plate surfaces.

A better way I know that works was patented by a an old friend who made million$ on this technology. You drive the battery, when it has a DC charger on it with low average duty cycle from the battery voltage itself . With a low power but very fast nS rise time >10A current pulses. It may not repair badly warped or corroded lead acid plates, but it will break-down the lead sulphate crystal growth on the plates which does two things. Reduces the specific gravity and lowers the effective series resistance (ESR) significantly.

If you want to research it. the old company or his patents before being sold to a major commercial transportation company, was called Solartech.

He told me the military tested it on Ni-Cad batteries in the 90's and was found to be very effective. Don't know about LiPo.

My theory on how it worked was... the pulses in ultrasonic range. created harmonics up to several hundred MHZ and all it took was a few to push any piezo-effect on the lattice structure in the crystal. He made the Bic lighter version that took a week to work. A couple guys from a Reno Ski lodge flew in their private jet to Winnipeg to meet my friend and I to offer a $1m for the patent. He refused. They had the blow torch method already working on rejuvenating large batteries for remote ski lifts.. ( although they had a design flaw once where all the early model Air bags in the parking lot , false triggered via massive EMI onto the g sensor and opened all the air bags in cars in the parking lot...) ( !! too funny ) guess they should have filtered the cables.

  • 3
    This is almost completely irrelevant to the question. – Dave Tweed Oct 19 '12 at 22:05
  • What a great story! – KyranF Oct 22 '15 at 2:00

A better way to revive a lead-acid battery is to use a desulphator. There is a similar thing i know of for NiCd. I would not use this kind of thing for any other type of battery. I have tried it on several lead acid batteries with success. It does not always work as a cell sometimes is shorted and driving high voltage short pulses can not do anything about that.

Especially not for Lithium batteries, as explained above.

protected by Dave Tweed Oct 21 '15 at 23:13

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