How To Revive Dead/Deep-Discharged NiMH Batteries Easily

Recently, my Roomba (iRobot) wasn't charging as it was kept for 2 years as it is.
I pulled out the battery pack and found that it's voltage was only 0.37v which means all the cells were deep discharged and probably dead. I put apart the battery pack and found 12 cells each 1.2v 3000mah capacity C type NiMH batteries. Then I measured voltages of all of all of them. Some measured 0.01V, some 0.04V and some 0.03V, which means all of them were dead. I tried charging them separately from my Nitecore Smart Charger but it showed an error.

I was going to dispose them off, but on doing some research I found out NiMH cells have good life and they don't die that easily. They can get deep discharged and can be revived easily unlike lithium cells. This means the cells aren't really dead? In most cases, yes.

So I found this great trick to revive dead NiMh batteries. To my surprise, it worked! You just need 1 cell that isn't dead (fully or partially charged) above 1.2V. Luckily I was somehow able to charge one cell from my charger directly. I don't know how that happended.

In this video, I am going to show you a simple trick which can revive your dead batteries in less than a minute. From 0.01v the voltage rised to 1.25v and then I could charge them normally with any compatible charger. Might not work in all cases. Make sure to charge the batteries within half and hour as they are not going to hold the increased voltage for long.

CAUTION: This trick only works for NiMH batteries which are 'rechargeable'. Don't try this with lithium/alkaline or any other type of batteries!
Even for NiMH batteries this MAY NOT work.
Perform this experiment at your own risk.
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[DayTradeJourney]

Wow! It worked! I was able to revive a 20-year-old 6-cell ni-cad battery pack for my old RC car by doing your method. It's like jump starting a dead car battery!

[IntelliAli]

Thank you so much. I know great deal about batteries but this never occurred to me. I threw 2 x DEAD 1.2v 1300mah niCd batteries in the bin. after seeing your video, Both now charging and working fine now. Thank you for making this video.

[johndopedo]

You can also use a 4.2v Lithium battery. I've done it hundreds of times--but you should only let it touch it NOT for 10 seconds, but only for 1 second at a time, keep checking the voltage or til the charger will recognize it. I've done it with a 12 volt battery too, but the batteries were 1.2v and like 4000mAH. Again, only touching MOMENTARILY until the dead one "wakes up". If you don't see a little spark, you got a dead/high resistance/open/ bad battery.

[stegususcley]

Havent tried it yet, but I got put all my old rechargables that I saved for some reason.ALL have said hhis works, and the same response from viewers on similar videos.
I believe it will work and thank you ahead of time.You and others offering this technique across YouTube are saving folks a lot of money.
2 thumbs up bud.👍👍

[lakyljuk]

It worked! Dead battery had 0, 120 V and charger marked is as faulty. I connected it to good battery and after 15 seconds or so, I put dead battery into charger and it started charging it, thank you so much.

[enoh]

isn't this just a voltage effect? Can't you apply 1.2v or so, from any source to revive these individual cells? The dead cell doesn't know anything about the chemistry of the donor cell :)

[mountriscan]

very nice video!!!Sure we would like the reassemble video of the battery pack.
let me know, did you use the same cell for reviving each one of the dead ones?or did also exist and another cell with enough voltage too which you used in addition?

[isaisthere]

You saved my life bro.. 3 sets of 5000 mah was about to be thrown away. They are charging now.. Thanks alot.

[pocketgamerz.]

Thank you for the guidance. I was able to restore mine. Cheerssss

[thzzzt]

This worked for me. I have the PowerEx MH-C808M charger and had some dead (0v) NiMH D cells. The charger simply wouldn't recognize that I inserted them. I used a new alkaline D cell to "jump start" as shown, except I held the wires for 30 seconds rather than 10. Then the charger at least recognized the D cells. I ran the cells thru a "condition" cycle, a feature of the charger, which took a few days, and the batteries seem good now.

[alexherrera]

NIce video.. ihave a battery pack of two batteries..one seems to be death and the other not, do i neeed to remove plastic cover in order to try this?
thanks

[Blarnix]

Can you make a video on how to disassemble and reassemble the roomba battery? That’s the part I’m nervous about.

[malayaka]

Is it still OK if I buy AA nimh with production date Oct 2020? Thank you

[zfjnyrr]

good vid! how do tell the difference from + or + wire? And do make a reassembly video of the Roomba pack.

[OmarDelawar]

Awesome tip Saiyam! Shukria! I am going to try reviving my old cells now.

[hunbrian]

Could anyone give me description about the science of it? Why does it work? Thank you for your video!

[kafakoparan]

My varta NiMh AA batteries are able to be charged normally but not with quick charge mode. What is the problem of these batteries? They were quick charging before without a problem but they now only charge with normal charge mode.

[raimolewing]

Great presentation, Saiyam. I have two Roomba battery packs dead due to long use interruption. Before disassembling them, I would like to see how the cells are rebuilt after the charging. Could you do a short video of that too.

[enchodus]

great, thank you!! May I ask a question, I have a couple of dead AA NIMH batteries that I want to revive, my other working batteries are D cells of the same type, can I use a D cell to revive an AA cell?

[kaganarisut]

hello . nice video. how can we deal with memory effect of these dead cells? after reviving and allowing them charging regularly, they still have memory effect and dont go up to their highest capacity. Is there a trick for this? I sometimes do a discharge and charge cycles but didnt get success