18650 Deep Drain Fix (DEBUG)

About: just an american white kid with a habit of somehow sounding british at times and having blonde hair and blue eyes. Wait this isn't a dating site.

Intro: 18650 Deep Drain Fix (DEBUG)

I couldn't let good samsung 18650's go to waste.

Step 1: Recharging a Deep Drained 18650 Safely

Recently I was lucky enough to find a Ryobi battery pack in the local hardware store's recycling bin. I was curious, they were fairly new and had true samsung 18650's in them. I took it home opened it up and put the 18650's on my very nice Liitokala USB battery charger.

Charger Link: https://www.amazon.com/Liitokala-Smart-battery-Cha...

However, the 18650's were drained so low that the charger mistook them for fully charged 1.2V NIMH batteries and did not charge them.

This was a problem. 18650's run at 3.7v, not 1.2V, and these were too low to charge.

What could I do?

Step 2: Parallel Charging.

In this photo is my 8x 18650 battery bank. It uses 1 to 8 18650's to charge up to three cellphones and power one LED light. The pink cells were from an old laptop battery. while originally 2,400Mah they appear to run at a third of that.

I replaced one pink 18650 with a green one and waited. A few seconds later (10 ish) the green samsung battery was at 3.1V, just enough for the regular charger to recognize it.

I performed this with the battery charger board (blue board near cluster of wires) unplugged, so the pink cells were charging the green cells. Now I had enough 18650's with enough power to be charged.

Charger instructable coming soon.

Step 3: Wait a Minute...

So I know what you're thinking.

Why not just plug in the controller board and let that charge the samsungs?

1) the fully charged pink cell would charge first and stop the charging. That's the drawback to parallel charging. Or, the pink cell would drain itself to equalize with the samsungs, and render itself deeply discharged.

2) I'm not sure it would have worked with entirely samsungs.

Most batteries should not be drained to zero percent. The blue charger board stops charging phones at 3.2V volts and stops charging batteries at 3.8V , so I'm presuming until proven wrong that 3.2V is considered "discharged".

Link for charger board: https://www.amazon.com/gp/product/B01MQG9N0S/ref=o...

Link for 18650 holders (they're flat top shock proof, meaning they're hard to remove but won't bounce out when dropped.) https://www.amazon.com/gp/product/B073WD82WZ/ref=o...

This is how to parallel charge a battery. If this is too much, remember how to jump a car, positive to positive, negative to negative.



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    2 Discussions


    11 months ago

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    1 reply
    Courier Sixtomatoskins

    Reply 11 months ago


    Understandable, I'll remember that for next time. I already did the project and I thought afterwards "Those guys would probably want to know this." Thanks.