Hello,
I pulled out 4 18650 cells from a laptop pack. One of the cells charges to 4.2 volts but when used in a DIY powerbank, it charges the phone for less than a minute and the powerbank shuts off. I tried a new Samsung cell in the powerbank and it works. The 4.2v would indicate the cell is healthy but not delivering the charge? Is it possible to fix this.
I would say try it in a flashlight to see if it discharges. If not, i wouldnt mess with that cell any further. Theres not really any fixing a cell. If theres something not right with a cell, discard it because its not worth the risk.
Unlike the samsung cell, its not as bright in a flashlight. I thought volts equaled to the capacity?
Depends how much charge time it takes to get there—the longer the more capacity—they sound like low quality or just worn out cells
Most likely that battery has very high resistance already.
I’ve tested a number of batteries that some acquaintance donated to me (most are actually not “usable” but I experimented on them anyway).
Out of a bunch of (mostly not-really-usable) 18650s that acquaintance passed on to me, a few would still charge and hold the charge (but voltage will drop a bit). Using IR check of analyzing charger, they got around 400-600mOhms IR.
Tried testing on a Convoy S2+ and then tested the tailcap current, they could only provide around 1.5A (supposed to be 2.8A on a good battery), making the flashlight noticeably dimmer, even when it’s just “fully charged” (unlike a good battery, even when not fully charged, say still at 3.9v), that good battery can still provide nearly 2.8A (and corresponding brightness).
So that means the high IR battery cannot provide enough current. In your case, when used on the powerbank, if you’re discharging at a low rate, it probably will still work (say 0.5A discharge), but if you’re discharging at 1A then the voltage sags and it’s not able to provide enough power and the powerbank likely shuts off to “protect” the battery.
Voltage means very little in determining a cell/battery’s health.
Your cell can’t sustain any practical load, which causes the cell to crash and burn.
You should always approach laptop pulls as ‘tired’ cells, unless the pack is brand new and you just like destroying stuff.
If you had a TV remote control that took 18650s, you could probably use it in that, but we don’t have those.
Recycle.
Chris
If the cells suck, they suck, put them aside for recycling.
But, used laptop pulls don’t necessarily suck. I have a lot of used Sanyo 2,600mAh cells that are still good for ~2.5A lights, other than reduced capacity. Of course, given that good quality new 18650s are cheaper and easier to get than they were when I got the packs, they aren’t worth much effort.
Yet…
I await the BLF TV ROP (“remote of power”) project with bated breath.
Don’t like the TV noise coming through the wall from your next door neighbour? Fire the beam out your window, bounce it off the house across the street and back through the neighbour’s window. Zap, volume down and problem solved. Optional constant-mute mode also available, just leave it lying on the windowsill 
It appears they cant take the load to charge cellphones. But I am able to run a 4G WiFI dongle for 24 hours. Using a Haweel 2 cell powerbank.
Don’t laff. I was thinking exactly something along those lines, or at least an IR repeater that you’d beam into the repeater from the remote, and it’d “broadcast” 20W of IR goodness into the general area where the offending teevee happens to be.
’Though mute usually toggles off/on, so while you can drive ’em crazy by having the sound flick on’n’off every second or so, it won’t keep it constantly muted.
Just an occasional burst of volume-down every few seconds might suffice, though.
I got a few of those luggage-tag-sized universal remotes that I could use as the signal source. :smiling_imp:
I did some work at two SEARS stores that were closing down and be liquidated earlier in the year, here in SoFla and I was given two 12v, 9Ah Duracell marked SLA/AGM batteries.
Since they were used and who knew how old they were, I brought them home and charged them up. I could get them to charge up to 13.05v with my Battery Tender Jr., but they’d soon settle down to 12.75v, which is still about 75% of rated capacity on its face.
The other day, I had them out to top off and decided that I’d hook my Maha C9000 to one of them and charge up 4 AA Eneloops. I set the charge to 500mA and started fiddling with other things. Upon inspection, 1 bay had stopped charging and the other 3 were down to 150mA, so I started things over and the 12v was just not up to the task. I got the wall wart out and finished them all off at 1A.
I have a couple of 02 Cool 12vdc fans for hurricane season and I’m sure that I could still get the fans to run on hi/low, for a bit, but that’s about all I can probably hope for?
I should just recycle them and be done with both, so we’ll see.
Life’s short and whether you can find a use for a ‘tired’ battery/cell, is ultimately up to you, but I’m starting to ‘bin’ a lot of these and opting to buy new, fresh stuff.
Chris
I noticed the cells are very very hot to touch at 4.1 volts on a charger. Is this amount of heat normal?
What current are you charging them at?
Could they be LiFePO4 ??? (yikes)
You need to recycle those cells ASAP. I’m a bona fide ‘thrill seeker,’ but if they’re hot to the touch (relative,) then their I.R.s have built up to such a level that the charger is having trouble charging them up.
Ditch ’em and find something else to tinker with.
Not worth it, IMO, but ‘you do you.’
Chris
Im all for pushing battery boundaries but when a cell is over 125 on “my” resistance tester it gets recycled.
Sans IR tester, Any 18650 that gets warm (not barely warm, or sort of warm) but warm let alone hot when charging also gets binned.
who really charges at 4-8 amps per cell where warm or hot would be normal?
I really should have known… :person_facepalming:
In my defence, I didn’t hear about BLF until sometime in 2015
An 18650 in a TV/AVR remote is overkill, IMO.
Sure, it can be done, but what’s the point?
Chris
Well, we’re not talking about ONLY upgrading the power source! You should check the thread I linked above. 