I have a set of 4 AA Eneloops (basic version) that I’ve had for over 6 years. And they’ve seen very little use. I’ve had them housed in a Nitecore EA4. However, I’ve always made sure to do a lockout, both electronic and physical. But… it seems I may have screwed up. I had the flashlight sitting for about 6 months. I took it out and it was totally dead. Checked the cells? My battery tester was blank for each cell.
I took the dead cells and inserted them into my NiMH 4 bank charger. Only one showed signs of charging – the rest were blank. The chargeable one sat in the charger overnight. It gave a healthy voltage indication once done, 1.46v.
I heard of a trick where you connect a good battery to a dead battery of the exact same brand/voltage for 10~15 seconds, and the influx of power “restarts” the cell. I did this for all 3 dead cells. Sure enough, they showed voltage. I put them in the charger and they’re actually charging OK so far. Not warm to the touch.
These are old cells, but they’ve not had very many cycles. Perhaps 25 tops. I’m wondering if they’ll be any good…
On a side note, has Eneloop improved battery chemistry over recent years? And is there any point of getting Pro? (quite a bit more expensive).
Often the hardest part is getting chargers to charge 0v cells.
Given you’ve achieved this, I’d cycle the cells and then test the capacity if you’ve a charger with this feature.
From the graphs I’ve seen, the Pro’s “wear out” faster, if you need the extra capacity and will use them regularly to justify the higher cost, then I guess they’d be good.
Else you could buy the Ikealoops (Ladda) if you’ve an IKEA nearby or one that delivers, I’ve found them to be much more reasonably priced than Eneloop.
I have depleted eneloops and ladda ikealoops to almost zero volts. They charged again perfectly and worked perfectly for years (still working) but I have not measured nor capacity nor internal resistance… but… When I charge them, the Smart chargers I have dont even report them with high internal resistance. They are very good batteries the eneloop!!!
(if you fully depleted eneloops, if the resting voltages IS below 0.7v you should put them to be charged in dumb chargers, then, after resting voltages goes above 1volt put them on smart chargers… (Most smart chargers dont charge the batteries of voltage IS below 0.6v)…
Then 2 things may happen:
1- the smart charger refuse to charge because too high internal resistance (never happen to me with fully depleted eneloops, but other brands It has happen to me, that the charger refuse to charge because of too high I R)
2- The smart chargers reports high internal resistance but charge them anyway
Thanks. Yeah, given how few AA flashlights I’ve got, I’ll stick with standard. I just saw what you mean by the number of cycles and Pro most definitely wear out faster. I do have an IKEA not that far away, and will make a point of picking up their cells next time I’m close by.
Good to know. The battery tester I used is a very basic one. I didn’t have my Fluke mm handy, but it would’ve been interesting to see what voltage it would’ve detected. I had the 3 cells going on a NiMH dedicated charger first, and after reaching 1.39v, I switched them over to my Fenix smart charger. Unfortunately I don’t have a load test feature on it. But not critical.
Is it generally a good idea to top off then run down in constant use to about 1v then charge back up again?
Hard to kill an Eneloop.
Charge them and just use them good a couple times and if not getting hot on recharge, good to go.
They are not prima donna’s like Lithium.
Party on!
Taking NiMh down to 0 volts is hard on them. The older or worse quality the battery, the less well they take that. It can be harder if they are in a series as one always dies first, and the rest may still be putting out current if the unit is in use. This can reverse the current through the dead cell which does more damage.
In your case, they probably just all died of ‘neglect’.
I’ve got a LOT of NiMh of all types and ages working in motion controlled small lights all over the house. “Dead” happens occasionally, and usually in series. The vast majority of time they can be revived in a dumb charger. If that doesn’t work, a direct short with a full cell will do it…usually. If not > recycle time. The older +higher IR the more likely to never revive, which makes sense to me.
I’ve been doing this for over a decade and have old Energizers, Ray-O-Vac, Kodak, and yes Eneloops that have been taking this flogging and are still working.
The batteries I’ve found that seem to absolutely fail the first are the HIGH capacity/non-LSD type. “Pro/High Capacity” seems to be mostly marketing hype, they are not good for the long haul.
Resting voltage for those cells the next day is 1.38v. Seems they’re OK.
Also, I discovered that I was mistaken – the EA4 has no physical lockout. I always engage the electronic lockout when the light isn’t in use. But it seems there’s some parasitic drain afoot. I’ll have to put in a spacer to block the circuit, going forward.
cells the next day is 1.38v. Seems they’re OK. 
