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Well, you'll have to work for it so it isn't totally free. Basically, MANY lithium battery backs can be reset back to almost new condition. I don't fully understand the reason the "smart" internal controllers become dumb and require a reset. I also don't understand why manufacturers don't provide the reset function on the I/O pin so you would not have to disassemble the pack. At one time, when lithium first became available, that function was on an I/O pin.


Tools needed:
X-Acto knife, plastic separator tools, screwdriver, etc. depending on battery pack construction.
Voltmeter - can do without it but it will give you a level of confidence
jumper wire
internet connection - to get info
magnifying glass - for us old folks

This will not be successful on all battery packs. Some will actually have bad batteries. The symptom is that the battery runs down VERY rapidly and also charges to full charge VERY rapidly. Well, full charge as indicated by the computer. The problem is that it is not really fully charged, but the "smart" controller in the pack thinks it is, shuts down the charging, and tells the computer that it is fully charged. If it runs down fast but takes a long time to charge or never attains full charge then resetting may not accomplish anything except give you practice for the next time.

I have done this successfully on at least three different battery packs. The first one was from a Micron laptop. It was VERY easy to do as lithium battery packs were just arriving and the manufacturer was smart enough to include the reset function on an I/O pin so disassembly was not required. It was a matter of shorting the pin to ground for a few seconds.

The second one was a Dell 8200 with 2 batteries. One of the batteries began exhibiting the symptoms. Unfortunately, at this point manufacturers did not bring the reset pin to the connector as it was on the Micron battery. This is a BIG mistake. MANY battery packs can be brought back to life simply by resetting them saving people lots of money and recycling costs.

Here is the deal. Battery packs have a built in smart controlling system. This is required because of the disastrous consequences of over-charging or over-discharging the lithium batteries. The smarts is a special purpose microprocessor. It has memory and monitors each battery or set of parallel units. The memory’s purpose is to build a database so that it can determine when it should tell the computer to shut down to prevent the pack from over-discharging. It also insures that the batteries fully charge to equal voltages.

Sometimes it goes dumb and the data tells it to stop charging the batteries too soon. I may also tell the computer to shut down too early. Again the symptom of this is a short time to recharge and a short discharge life. To my knowledge, ALL of these microcontrollers have a reset pin, at least the two I have looked up so far have. The reset will clear out this bad data and allow it to start fresh.

So, back to the Dell. I decided to disassemble the pack to figure out if I could reset it. I carefully separated the clamshell plastic cover; pulled out the PCB (not disconnected) that has the charge monitor circuit on it, located the microcontroller, looked up the specs to find the reset pin, and shorted it to ground. I then replaced the PCB and put the battery back into the computer to charge.
This time it took a long time to charge – as it used to. When I ran it on battery, it lasted almost as long as it did when it was new. SUCCESS!

OK, I still have the Dell, but the batteries are way overdue to replace. But now I have a 5 year old Averatec and I have replaced the battery once already. It is now seldom used – only when I need to run XP. The battery started exhibiting the same symptoms as above. It also would go dead in a short time just sitting in the off condition (not sleep). Time to try again.

I carefully separated the glued clam shell plastic and opened the case. The trick to separating them is to figure out how they went together. In this case, I carefully inspected the obvious separation gap to determine which half went INTO the other. Other battery packs may be screwed together or just snapped together. This is the hardest part, figuring it out and getting it open. Sometimes, multiple methods are used and screws are often covered with labels. You can find hidden screws by running your nail or other dull object, like the back end of a ball point pen, over the plastic. If you hit a soft spot it MAY be a screw hole. It could also be a mold mark in the plastic. You will have to dig to find out.

Sometimes none of this is “obvious”. Once I determined this I slid an Xacto knife into the split.

It went in pretty easily. If I had chosen the wrong side it would have been more difficult as I would be cutting plastic and not glue. I then ran the knife all around the case till all sections were loose. Be sure to insert knife at a steep angle so as not to damage anything inside. (Do be careful, those knives can do bodily harm.) Off it came. There were no screws.

This unit has 8x 18650 lithium cells arranged 2x4. The capacity is 2x whatever one cell is. That is difficult to determine from print on the cell since there usually is none regarding AHr and if there is it is usually an overstated lie.

I then measured the voltage on each parallel bank of cells. They were all pretty much the same. Shutdown voltage was 3.7v or about 14.8V total. Fully charged it was about 15.8V. This pack was pretty easy, some are not because of how they are arranged or the lack of convenient points to place a voltmeter. It may be difficult to determine how they are connected. I had one pack that I had to remove the batteries to figure it out.

As you can see, this pack is 2x2 in line with a wire going to the PCB from each junction. Note that there are three protection devices – a thermal fuse (silver cylinder), a thermistor (covered in white adhesive), and a multifuse.

The monitor point wires are Black (ground), Green (1st cells), Yellow (2nd cells), Red (3rd cells), and main + (4th Cells). The Black wire is the main negative line. The Red wire coming from the end of the thermal fuse is the main positive lead and the 4th cells monitor line.

If the cell voltages are pretty much even, then there is a good chance the reset is going to work. If any cell(s) are very different from the rest (one cell being 2.4v and the others being 3.7v for example), odds are against a reset fixing things. Makita drill packs are famous for failing this way. However, I have revived one of those, but that is for another Instructable.

Now you must determine which IC is the microcontrollers. It is either the largest one or the one with the most leads.

Here you see a large IC with 20 pins and a smaller one with 32 pins, 8 on each side. My first choice is the smaller one. It is an Amtel Mega 168 (as read from the IC). I googled this and found a datasheet. It is indeed a microcontroller.

The data sheet info that I need is:
1. Which pin is reset? – in this case it is pin 29 or the 4th from the corner CCW with the index mark on it. I followed the circuit trace on the PCB to a resistor/capacitor junction (typical for a reset pin circuit) and chose that spot to use for resetting (the IC pins are just too close for me). As long as there is no direct Vcc pins nearby you can probably get away with an accidental contact to adjacent pins. Here the Vcc pins are on adjacent sides so I am well clear if I chose that.
2. Which level is reset? – in most cases it is ground. It is usually indicated by labeling "reset" with a line over the top – that depends on company policy. If there is a line, it is ground to reset. If there is not a line further reading may be advisable. Since I can't easily create an overscore I will use a "#" --> #reset.

I’m ready. I connected one end of a test lead (wire) to the black wire on the battery and touched the R/C junction slowly a few times for good measure. I plugged the battery back into the computer and plugged in the charger. This time it took over an hour to charge. A GOOD SIGN!

BETTER THAN NEW. But then it was a “NEW” fleeBay battery. Each set of cells is now 4.16V for a total of 16.64V.
When booted up after fully charging, the time to shutdown was 2.34 hours, up from 22 minutes before the reset. When the battery was "new" it was less than 2 hours. I think that was a successful endeavor! What do you think?

You may not want to glue the halves together too tightly. If you are lucky it will snap back together and hold without glue. If you are real daring, and you have an unattached pin on your I/O connector, you might consider connecting it to the reset point. (You will definitely need a volt/ohm meter to figure this out. Be sure to measure from both ground and V+ to the pin. Don't rely on following traces on the PCB.) 

Then instead of a disassemble, you just need to short that pin to the ground pin for future resets. Just don’t forget which one is #reset and which one is ground. Unfortunately, mine are all spoken for, but the lid has snapped back in place without glue.



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    16 Discussions

    Nikos Stavrou

    3 years ago

    Hi, very useful article.

    I am considering of doing the reset procedure at the battery of my laptop.

    I have opened it and the controller IC is the TI bq20z45 ( which has as you can see a RESET pin and a MRST pin that are active low. Do you think that would reset the controller IC.

    4 replies
    DavidP190Nikos Stavrou

    Reply 1 year ago

    i took my battery which is for a dell e6510 that would charge fully but degradation indicator showed it was bad. looked on board found pin but what i did was take a jumper one end to neg and touched briefly the test contact points. only found 2 that had juice but after that tested battery and now indicator shows 100 % charge and degradation at 0% (like a new battery)


    Reply 1 year ago

    love it when a plan comes together.........
    sounds like you found the MRST and a RESET
    both are active low
    just to remind people, this won't work for all bad battery packs since some will contain bad cells and a reset won't fix them.
    The reset only clears the memory of the processor. If cells are bad it will figure it out again but you won't get the voltage out of it anyway so it won't work in the unit.


    Reply 1 year ago

    the only bad is that the laptop built in diagnostics ( battery info in bios setup) still shows up as low battery health status

    ruggbNikos Stavrou

    Reply 2 years ago

    it looks like grounding that will do the trick. Remember the unit is power up all the time. try not to short out something else, though at 3v i probably won't hurt a lot.
    good luck


    2 years ago

    Great idea!

    I have a battery pack with a "Max1788A" Unfortunately there are no datasheets available for free, just directly from Maxim-IC, only for companies :( I tried to short all potentially reset-pins to ground, didn't help.

    1 reply

    Reply 2 years ago

    yeah, I couldn't even find a pinout for that.


    4 years ago on Introduction

    this is a link to the datasheet.
    if Master Reset (pin 27) doesn't do it I can't help any further.
    It worked in all the units I have done.
    The battery may actually be NG.

    Hi! Nice tutorial. I have Toshiba Satellite a300 and the old battery is 6 cell. I did everything but it didn't work is it possible that i need to modify something on the EEPROM or the processor rewrites it on his own??? The processor on my battery is max1781.


    4 years ago on Introduction

    Nice tutorial. I will try this with my dead Lenovo 6 cell battery, as all it's cells measure 3.7 volts, but the battery isn't being detected.


    5 years ago

    I don't know anything about all the technical stuff of this, but I have 2 laptop batteries that charge to quick & die quick. I could take them apart but I would have a clue what everything is or does. Do you have a "For Dummies" version of this? It would really help.

    1 reply

    Reply 5 years ago

    unfortunately, that is as simple as it gets. Maybe u can find a techy friend to can do the details. the biggest problem after getting the case open is IDing the processor and getting its specs so u can figure out which pin to short. The only thing u don't want to do is short raw + and - together, though if the battery is basically dead it won't do to much.
    I could tell u which one I shorted but there r different processors used and that won't help.
    the pc board that the circuit is on may be tricky to get a look at the chips on it. The processor will probably be a chip with pins on all 4 sides but there might be 2 like that. U just have to get the numbers off them and do a google to see which is which. After 50 years, I guess pretty good.
    good luck.


    6 years ago on Introduction

    What are the potential drawbacks of this method? Is there any harm that could come of the cells if you reset the micro controller? E.g. micro controller allows too much charge through and fries the cells?

    1 reply

    Reply 6 years ago on Introduction

    I experienced no problems in the 3 I did.
    The micro is built for this purpose. Why it goes of into left field I don't know.
    Resetting it just puts it back where it was when it was first connected
    Then it resumes its job correctly. You can't make things much worse since the battery is useless the way it is.
    If u are very clumsy you could short out the wrong thing and fry some parts. If you try to short at the controller pins you need a hat pin, great eyes, and steady hands.
    Thought I suspect most controllers won't have a Vcc pin close by - which is about the only thing you don't want to short to ground.
    It isn't too technical. you just need to be able to find the controller data sheet and read it. Then all you are looking for is Reset and how close Vcc pins are.
    That is why I suggest finding a bigger target by following the trace. That, however, may not be as easy as the one I just did. The Dell I did I used the IC pin. I am sure I must have touched the adjacent pins, but they were I/O pins and not Vcc pins.


    Reply 6 years ago on Introduction

    This works on battery packs with a controller board. It may work on single batteries with a built in controller. The only issue is, I believe it is impossible to get to the reset point without destroying the battery. But you have nothing to lose trying to do it on an otherwise useless battery. Just make sure you don't breach the battery. If the controller is separate from the battery, IE in the ipod, then unplugging the battery should reset the controller. But I haven't tried it.