beginner question about eneloops

[Special K]

I have read the following claim about eneloops:

Maintain 75 percent of their charge after 3 years of storage

Does this mean that:

After 3 years of storage, the eneloops will have 75% of their original charge left, and if I put them into a charger, it will be restored to 100%.

or

After 3 years of storage, the eneloops will have 75% of their original charge left, and this becomes their "new maximum" charge (i.e. you will never be able to get them back to their original 100% charge).

For some reason, I was under the impression that the max amount of charge a rechargeable battery can hold decreases over time. Is this correct? Does this occur through regular discharging/recharging of the battery, through storage and non-use of the battery, or both?

 

[VidPro]

it means if you neglected the battery for that long (3 years) you might see some output out of your flashlight still :-) that is if your flashlight or device had Zero tiny drain, or the batteries were not stored in the device.

after even 6-7 years the eneloop can be made to function to ~100% , so no unless it was damaged, or damaged by reverse charge, or a bad item. You should be able to get it to work at ~95-100% again, mabey with a bit of coaxing , like breaking it in again, or cycling. As robust as they are, it is more likly that the Way they are used, the way they are charged, and the way they are maintainced will effect them more than them self destructing.

Yes it is true that there are many ni-mhy cells sold even today that the max charge goes to heck, that the self-discharge starts getting higher, but eneloops generally hold out for time many times better than those did and still do. Yes it is also true that the way many of the batteries are used (even by myself) reguardless of brand they can be damaged and reduced in total holding capacity.
This all assuming that it is a real sanyo eneloop thing and not a knock off. other LSD cell items can do much better with all that , than they did before also.

 

[Wiggle]

It is moreso Li-ion based cells that depreciate on a short(er) time scale. Depending on how you treat them that could be as short as a couple years to noticeable capacity loss. NiMH seems more robust and with conditioning, older cells can generally perform quite close to original levels especially higher quality ones like Eneloops.

So basically, after 3 years 25% of the "fuel" will have leaked out of the battery's "tank", but the tank can still be filled up.

 

[Yoda4561]

The 75% figure refers to the self discharge, you can use them until the battery is drained at that point or recharge them, and they'll be back up to 100%, they do degrade over time as all batteries do, so at 3 years it would probably be more like 99%.

 

[Special K]

The 75% figure refers to the self discharge, you can use them until the battery is drained at that point or recharge them, and they'll be back up to 100%, they do degrade over time as all batteries do, so at 3 years it would probably be more like 99%.

That's still pretty good. Is the degredation of the battery's max charge capacity affected more by time or by the number of charge/recharge cycles?

 

[Special K]

It is moreso Li-ion based cells that depreciate on a short(er) time scale. Depending on how you treat them that could be as short as a couple years to noticeable capacity loss. NiMH seems more robust and with conditioning, older cells can generally perform quite close to original levels especially higher quality ones like Eneloops.

So basically, after 3 years 25% of the "fuel" will have leaked out of the battery's "tank", but the tank can still be filled up.

What exactly do you mean by "conditioning"?

 

[Yoda4561]

It's hard to say what the defining factor is in charge capacity degradation, but I'd say the #1 that you need to concern yourself with is keeping the battery within its safe voltage range. Don't use a charger that overcharges the battery, and don't drain the battery below 1v, and you'll probably lose the things before they wear out. Eneloops do have a manufacturer cycle length rating, so if you recharge the battery once a day or more often you'll hit the charge cycle limit before a properly stored battery would degrade significantly.

 

[Wrend]

What exactly do you mean by "conditioning"?

There are some mixed opinions about this out there.

A few slow (low rate) full discharge and charge cycles can help get NiMH and NiCd cells back to performing like new. This may be due to the redistribution of electrolyte and/or the "reformatting" and breaking up of larger crystals within the cells. The break-in function on the MH-C9000 charger works well for this for NiMH cells (provided their internal resistance hasn't gotten too high) after a slow 100mA discharge, for example, and tests the cells' capacities.

It should be noted that Eneloops really don't need much maintenance in this regard and there is less performance loss over time and less to gain back from cycling, especially compared to some other lower quality NiMH cells. Cycling them too frequently probably just adds more wear on them. But on the other hand, they have a pretty high cycle life potential at their disposal.

My 4 year old first gen. Eneloop AAs (08-11) are still performing like new (within the typical range of new Eneloop cells), and I would estimate that they have lost maybe a little over 1% to 2% of their capacity potential. I don't know for sure though, since I didn't test their capacity when they were new (didn't have a C9000 yet).

 

[AnAppleSnail]

In short, use 'em like they are magic energy tanks. Get a good charger that will take care of the cell though, and try to avoid overdischarging them, especially in multi-cell applications. The self-discharge levels out at about 75% capacity, with one CPFer testing his new-in-box 2006 Eneloops at nearly that available charge. These cells also appeared to charge and accept normal loads thereafter.