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Repairing a LIP-12 battery (MZ-R30 and such)

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Disclaimer: I cannot be held responsible for whatever damage or loss, physical or mental, related to attempting to repeat something described in this post. It is provided for educational purposes only. Never disassemble electronic devices, especially batteries and battery packs, especially lithium ones, unless you have necessary proficiency and qualification in electronics.


Recently I’ve acquired a Sony MZ-R30 Minidisc player.
It’s a kinda fun format, but the fact that I had to use a 2AA case in order to enjoy my music was quite disappointing.

After fiddling around with the dead LIP-12H that came with it, I came to a conclusion that it’s definitely a somehow packaged 18650 cell.

Carefully prying it apart with a hard plastic spudger and an X-acto knife, here’s what I saw inside.

Note: better pry in a direction outside the pack, as not to damage or short out anything

And once you get the top case off...


Sure thing, it’s a 18650 with a small protection/driver module.


The battery turned out to be a Sony Energytec US18650S STG ICR Li-Ion cell. The voltage measured around 0.86V, so it’s definitely going to be discharged and then handed in at a battery recycling point, along with some others undercharged ones.

To remove the battery, I cut the long positive zinc terminal behind the cell by bending it a bit outward, and carefully cutting the zinc stripe in half.

Then I pulled hard on the cell and it detached from the bottom negative cell tab which was soldered directly on the protection circuit. Afterwards, pulling the remaining positive tab got it free. Don’t throw them away just yet, instead make them nice and flat (and cut off the “tail” of the positive one”).

For easier working, I also cut the remainder of the positive tab’s tail that was still attached to the protection board so that it would just form a soldering pad on the board itself, instead of completely desoldering it.

Now I had to find a replacement cell.
I’ve done a big old laptop battery teardown this summer, and even though 2 of the salvaged ones were already undervolted, and 4 more were rendered useless by lending a 18650 powerbank to a classmate who let them down to 2.05, I couldn’t get myself to buying new cells, and that’s why I kept the tabs.

It would be great if I had a Li-Ion cell welding machine, but so far, I just went on and soldered a piece of wire from an ATA (IDE) cable onto the remaining square pad, and the other end onto the remaining zinc tail on the positive input of the protection circuit.

Then I picked a replacement cell, my choice was a Panasonic CGR18650C, because they seemed to be somewhat good looking and are what I had at hand (I have plenty of other Sony ones, but just 2 of these after the other 4 ones died, which doesn’t even make them a viable powerbank set :P).

Finding datasheets for both original and replacement cells was a hard time, but, from what I could tell, the Panasonic ones can easily survive 1428mA charging current, and the original Sony one had a 1C rating, thus, a 1350mA maximum charging current. So, since 1428mA is less than 1350mA, we should be safe  :)

Afterwards I used some electrical tape to secure the pads to the cell, because as you should know by now, one should never ever solder directly to a Li-Ion cell, and I don’t have a cell welding tool.
I made sure it’s as tight as possible so that the playback would not interrupt, and then secure the cell to the original casing.

The top cover, however, decided not to fit onto such a strange construction, so… you might try and do better :)


Yeah, that’s not something you would be fine with taking out at an airport or something:D

Sliding it in also became a bit harder than it was originally, because of the changed size, plus one has to observe the wire so that it won’t get stuck in the way somewhere along the slide and short out onto the case (should’ve used more electrical tape, yeah).


The player is now back to fully working order! Now I can enjoy my music without stretching my pockets due to the overweight external AA battery compartment size.


Charging the battery inside the player right now with a Sony PSP 1.5A charger and the battery doesn’t seem to even get any hot, even though the battery gauge shows weird things, so I’d call it a success. Not the best way it could be done, but clearly a success.


Let me know if it's helpful :)

- Ak.

Edited by akasaka
R50 needs a different battery
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Stand by for much spudging! (For the ancient of those of you reading, I am irresistibly led to suppose that this tool originated in Much-Spudging-In-The-Marsh, with apologies to Kenneth Horne and the BBC). Will be a week before I have it though, With your skills you will probably have figured out a solution by then :)

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  • 2 weeks later...

Lip-8 contains a very standard 14650 battery - easy to fit in the empty case - I just worked a blade around the seam, separated the case and pulled off the spot welded terminals with care (snipe nosed pliers did the trick for me). inserted new 14650 and reassembled the case around it. - Usual disclaimer about safety - Please note that I am only describing what I did, not how to do it yourself - Lithium batteries need special care.


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  • 1 month later...
On ‎29‎/‎01‎/‎2016 at 4:50 PM, Sphig said:

Lip-8 contains a very standard 14650 battery - easy to fit in the empty case - I just worked a blade around the seam, separated the case and pulled off the spot welded terminals with care (snipe nosed pliers did the trick for me). inserted new 14650 and reassembled the case around it. - Usual disclaimer about safety - Please note that I am only describing what I did, not how to do it yourself - Lithium batteries need special care.


Was the 14650 bttery you used the same mah as the original? Any downside to using a higher mah? Was the new battery you used protected? 

Same sort of solution for UK MZ-R50 users - MZ-R50 solution




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The 14650 was higher capacity - but this causes no problems - a side benefit is longer playtime. - Also battery was quoted as having protection built in - however, I didn't bypass the existing circuit in the empty case - just inserted the new battery.



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I'd definitely get a tabbed battery but I wanted to use something I already had at hand since getting decent batteries (not usual TrustFire, UltraFire, whats the next brand... HouseFire? crap) is mostly only possible by either getting old laptop batteries and pulling still living cells (but that's gonna be without tabs), otherwise that gets really expensive :c

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  • 4 months later...
On 2016. január 4. at 0:05 PM, akasaka said:

Let me know if it's helpful :)

It is, indeed.

And the reason I reply to a fairly old thread, is a similar experience, but with a little addition - a little hint (but a long story, apologies). It might work in some cases. Li-ion batteries are delicate on one hand, but on the other hand, due to the built in electronics, they can survive better, than the NiMH batteries for example.

(I understand in some places of the world it is advised to use disclaimers - without repeating his words here, please refer to the OP's disclaimer at the top of this thread.)

Few days ago I bought a small bunch of junk minidisc walkmans (for peanuts really), just out of curiosity, to see how they look like inside. I can tear them down without any fear, and I maybe able to learn new things. One of these was a Sony MD-R30, little beaten, but it turned out being fully operational, and just run nicely plugged on my MZ-R3's power adapter (even it was only 5V, while the R30 would have needed 6V, according to the sign next to the inlet). Then I noticed, that there is a battery in the unit. It looked completely dead, no voltage on the terminals, and it did not take any charge either. I decided to check it inside - I did not have any replacement battery, but I had an experience, that suggested I should try it again.

Few years ago, I once accidentally left a battery of my tiny Sony camera (DSC-T7) in the watch pocket (coin pocket) of my jeans. My wife did not notice it, and put them into the washing machine. It took me some time to realize where I left the battery, but by then the washing program was almost complete. Needless to say, the battery was completely drawn, worse than that, even the external charger indicated it was faulty.

I had nothing to loose, opened the miniature case, and disconnected the internal controller board from the battery. It showed only a few hundred mV, but it was a sign, that it is not yet completely dead. Then I connected the battery to a CC PSU (constant current power supply). At about 5 Volts, I began charging the battery with ~100mA current (* more about the value below), and monitored the voltage. It soon jumped up to ~3V, then I gave a couple of 5-10s impulses of 200...300mA, with equal length of "breaks" with 100mA in between. After this treatment I reassembled the battery, glued the case, and I have been using that battery since then, just like a normal one.

Based on this story, I gave a chance to this LIP-12 pack too. I assumed the unit has not been in use for many years, and it depleted the battery. An alkali or a NiMH battery would have certainly died, but the Li-ion is protected from completely discharged, by the internal controller board.

When I desoldered the 18650 cell from the controller board, it showed (what a coincidence) a similar 8...900mV. Then I performed the procedure above. I chose 200mA charging current, and 500mA for the impulses. The 200mA is about the 1/6th of the nominal capacity of the pack in mAh - the rule of thumb is 1/10, but while that is appropriate for regular charging a healthy battery, here I wanted to get some quick results. After a few minutes the voltage went up to 3V, then I repeated the impulses, finally, left the battery on ~150 mA for about ten minutes. At this time, it showed ~3,7V - that is good, as the nominal voltage of the pack is 3,6V.

I resoldered the cell on the board, reassembled the pack, a few little drops of superglue on the edges of the case, and it looks as before. When I slipped the pack back into the compartment, the unit immediately showed ~50% remaining charge (that instant value was a bit "fake", but definitely a good sign), and after plugging the wall adapter in, it began charging. Playback did not stop when I unplugged the power adapter, so the battery was back in life. I will experience a bit around the real capacity of the "revitalized" cell, but so far so good.

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Thanks for sharing the story NGY but there is an actual reason it is not recommended to charge lithium cells under a certain voltage. 


Basically every time you discharge a cell, one of the electrodes dissolves into the electrolyte. Up to some point, it's all fine because it's surface remains intact and when you charge the cell it will restore over that surface. However when it's overly discharged the surface is uneven and the copper (or whatever it was) will form uneven shapes and spikes, which can lead to puncturing of the internal insulation with all the fun stuff like thermal runaway and such. 


Can't remember the source of it, I read it in a book at the university library, but it stated it is applicable to both ICR cells and IMR cells. 

Glad it works for you but it's not quite worth the risk for anyone to repeat I suppose...

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15 hours ago, akasaka said:

Glad it works for you but it's not quite worth the risk for anyone to repeat I suppose...

Yes, there are risks here (as always are when "tinkering" stuff), and whether or not it is worth it, that is certainly subjective.

For better understanding those risks, let me add some more insight. In my post above I wanted to be as brief as possible (unsuccessfully), and left out the physics part completely (most of it will still be missing below though, but gooogle is there anyway).

But before that, supplement to the DISCLAIMER part: the thoughts below (just as the process above) are not meant to suggest/convince  anyone, that they can/should repair their battery packs this way.


15 hours ago, akasaka said:

 there is an actual reason it is not recommended to charge lithium cells under a certain voltage.

Yes, it is generally not recommended to recharge Li batteries, if the cell's voltage dropped below ~2,5V (according to most manufacturers).

And the reason for this is the risk of overheating the cell during the charge process (and as we know, Li batteries can even catch fire if handled improperly, i.e., terminals shortcut, overcharged, etc.).

How can it happen? Very simply put (without much of the chemistry part): the cell's internal resistance drops dramatically as the voltage lowers (and not even linearly). Regular charging current (in case it can be up to 1/1 of the cells nominal capacity in mAh, or more in quick charge mode) over this low resistance can overheat (or burst) the battery, and heat is one of the biggest enemies of the Li cells.

However, there is a reasonable range of this undervoltage in which a deeply discharged battery can be brought back to life, using an appropriate pre-charging process (GOTO DISCLAIMER).

800...900 mV is about the limit (or say ~25% of nominal voltage), when it still can be attempted to recharge the battery (highly depends on the cell itself though). And in the lights of the above, the first precaution is the initial charging current. (Advanced chargers do this anyway: at the very beginning of the charging process they apply a very low current, and as the cell voltage rises, increase the current).

The 1/10th (or 1/5...1/6th for the impatient) constant current is low and safe enough in most cases, not to burn the battery (GOTO DISCLAIMER). And yes, during the whole process the temperature of the battery must be monitored (I indeed forgot to emphasize this, but here it is now).
Those short impulses are still fairly below of a regular charging current, in terms of mA and the duration. I am using them for "pumping" some energy into the cell, to increase cell voltage to a level that the controller board would accept and happy to take charge.

From this point, if the battery's own charger accepts again the pack and begins charging it, the rest is business as usual. Heat still needs to be monitored, but if the cell was cold during those impulses, it should be OK (GOTO DISCLAIMER).

PS.: the MZ-R30 is running now in loop cycle after the "treatment" of this LIP-12 pack, I will report back, how the battery performs.

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On 2016. 08. 21. at 11:18 AM, NGY said:

PS.: the MZ-R30 is running now in loop cycle after the "treatment" of this LIP-12 pack, I will report back, how the battery performs.

After the MZ-R30 fully charged the battery, I have run a full discharge-recharge cycle: MZ-R30 laid on the desk, earphones attached, volume turned at 50%, play mode "repeat". I checked back at the end of every hour what the unit's display showed for remaining battery % (grey squares represent the segment blinking very slowly):


At the end of the 8th hour it was still playing, with some juice left in the battery, but I did not want to squeeze it more, so I stopped the device. Recharge took few minutes less than 5 hours, again inside the MZ-R30.

These values are very reasonable, even do match the specs in the UM (although conditions were very forgiving, compared to what a units gets during jogging for example) - that tells me that this particular battery pack had not yet achieved it's lifetime before it had been put down and forgot about.

My other try today on a Li gum stick battery failed though. I managed to get the "revitalized" cell accepted and charged by the device, but the battery did not hold charge, it dropped voltage in less than a minute. End of story.

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