Mostly Eneloop in Maha Discharge, Capacity & Health Questions

[awyeah]

The C9000 terminates charges pretty conservatively, so you likely don't have much to worry about either way.

True. Safety is one of the main reasons I bought that charger.

 

[LetThereBeLite]

The break-in function does a standardized capacity test. I discharge my cells first so they're not needlessly overcharged during the fist portion of the test. Using either 1900mAh or 2000mAh as the capacity for the AA Eneloops is fine for the break-in test; either will fully charge them. I personally use 1900mAh for the AAs and 800mAh for the AAAs.

This is a good tip--one I don't see in the Maha manual. I very recently purchased a 4-pack of Sanyo XX batteries. When I got them and was going to do a break-in, it occurred to me that I probably should not directly start a break-in as the XXs most likely had at least 1000 mah in them and directly performing a break-in would overcharge, albeit at a low charging rate, the cells. So I performed a discharge first--glad the Maha C9000 doesn't automatically recharge discharged cells. After the XXs were fully discharged, I started a break-in on them.

 

[Bolster]

According to Maha's FAQ:

Q: Using the BREAK-IN mode, I am seeing a charging capacity much higher than thecapacity I programmed. Why is the battery overcharged? A: When using the BREAK-IN mode, the charger puts in 1.6 times the capacity of the battery (entered at the start of the charge). This does not cause any harm to the battery as the charging rate is very low (only 10% of the battery capacity). The increased total charging capacity compensates for energy lost as heat. This is the charging scheme recommended by International Electrotechnical Commission (IEC).

 

[Wrend]

Yes, however, Eneloops (and presumably other low self discharge NiMH cells) come "precharged" at about 75% of their capacity, so doing a break in on them right away puts a total applied charge of about 2.35 times their capacity on them during the first charging phase of the break in.

Overcharging at these lower rates doesn't do significant damage to the cells, but it is my opinion that it should generally be avoided when possible and that it does add extra wear on the cells.

Also, more fully discharging the cells first likely helps to cycle their full capacity more and make the break in more effective. I haven't personally tested the difference, but there is another active member here who has reported noticing about a 50mAh capacity increase when discharging Eneloops first before the break in. I'm assuming that was for the AAs.

http://www.candlepowerforums.com/vb...oop-Break-In&p=3950050&viewfull=1#post3950050

Either way, it isn't really that big of a deal, just a better practice, in my opinion.

 

[45/70]

......there is another active member here who has reported noticing about a 50mAh capacity increase when discharging Eneloops first before the break in. I'm assuming that was for the AAs.

And just "who" might that be, LOL! Yes, that observation did occur when breaking in 20 AA eneloop cells. It may be important to note that all cells were run on one C9000, rather than the three I now have. The original C9000 developed a display problem after a couple years, and was replaced by Maha, so I no longer have it. So, did this particular charger have something to do with my results? Unfortunately, we'll never know.

I no longer have the data from that initial break-in. I did mention it in one of the Mega C9000 threads however. As I remember, I wasn't the only one that obtained similar results at the time, when first discharging the cells at a low rate (ie. 100mA) before running a break-in.

Since then, I have not run an initial break-in on any other eneloop AA cells. I had a large supply of "traditional" NiMh cells at the time, so have not purchased any since the original 20 cells. That may change soon, although for the past couple years I've been running primarily Li-Ions in most of my lights.

As for discharging LSD cells before running a break-in, sometime ago it was determined (maybe by SilverFox?) that LSD cells were more sensitive to damage caused by overcharging than traditional NiMh cells. This supported the idea of discharging cells first, before running a break-in.

All that said, many support the idea that no harm will come if the cells are not discharged first. So take your pick. IMO, it can't really hurt anyway, it just takes a bit longer, and it's entirely possible, from my limited experience, that there is a possible capacity advantage, as well.

Dave

 

[Bolster]

Yes, however, Eneloops (and presumably other low self discharge NiMH cells) come "precharged" at about 75% of their capacity, so doing a break in on them right away puts a total applied charge of about 2.35 times their capacity on them during the first charging phase of the break in.

Ah, good point. Well I'm sold on the idea of an initial discharge. Thanks.

 

[LetThereBeLite]

According to Maha's FAQ:

Q: Using the BREAK-IN mode, I am seeing a charging capacity much higher than thecapacity I programmed. Why is the battery overcharged? A: When using the BREAK-IN mode, the charger puts in 1.6 times the capacity of the battery (entered at the start of the charge). This does not cause any harm to the battery as the charging rate is very low (only 10% of the battery capacity). The increased total charging capacity compensates for energy lost as heat. This is the charging scheme recommended by International Electrotechnical Commission (IEC).

Bolster, .1C of a 500 mah battery is 50 ma, and thus doesn't sound too bad. But .1C of a 2500 mah battery is 250 ma. That, IMO, is pretty high. If the XX came with 1500 mah already stored in the battery, I wouldn't want to add another 4000 mah to them at 250 ma.

Just being as gentle on them as possible. I'm sure it wouldn't kill them if done once or twice but since the Maha C9000 has the ability to discharge without automatically recharging again, I think discharging completely is a good initial step in the break-in process.

 

[Wrend]

Yeah, at some point you have to take into account the extra applied power per volume or surface area (not just capacity potential) and how well the cell can dissipate the extra heat after it's full.

 

[Adriano]

Hi, today I have purchased a Maha C9000 and 4 Eneloop XX batteries. I'm sorry for my poor english and I don't understand fine the meaning of the BREAK-IN mode. Can you tell me how do I have to charge those batteries please? Thanks

 

[czAtlantis]

If you want to just charge them you don't need break in.
If you want to measure their capacity (for future reference...) and give tem 100% performance - run break-in (but before doing it run simple discharge).
Break-in is not necessary with eneloops - it is more useful with old batteries - it can "resurrect" them to have higher capacity.

 

[LloydV]

if the object is to "empty" a brand new eneloop before running the break-in cycle, does it matter much what the initial discharge rate is? i ask because dave (45/70) mentioned an initial discharge at 100ma.

my own practice is to use it out of the pack (which is the whole point about these being "ready-to-use") for whatever purpose - digital camera, toys, etc. - then do the break-in after that initial use. i suppose if one were to use it in a clock or remote, which would take far longer to "empty" the cell, this wouldn't be applicable...

 

[czAtlantis]

I always discharge them and run break-in for 2 reasons
A) I want to check them if they are OK and what capacity they have. I write this capacity to spreadsheet for future reference
B) I want them in my camera etc ready in 100% charge - not just 60% from manufacture

 

[45/70]

...... i ask because dave (45/70) mentioned an initial discharge at 100ma.

The 100mA initial discharge is optional. I no longer have any documented "proof" that it makes any difference, but at the time (several years ago) it appeared that I was obtaining ~50mAh or so higher capacity than those who did not discharge at a low rate first.

Anyway, discharging cells before performing a "break-in" on the C9000 doesn't hurt. Part of the idea of doing a break-in, is to mix the chemicals evenly throughout the cell. It makes sense that those portions that remain charged before performing the forming charge portion of the break-in, do not get mixed in as well. The lower the discharge rate, the more discharged the cell will be, thus a more even distribution may be possible. Whether using a 100mA discharge rate first actually helps or not, I really don't know. It did seem to make a difference when I did it that way however.

Once the first 16hr charge is completed, the C9000 discharges the cells anyway (albeit, at a 0.2C rate), so discharging the cells initially, effectively adds one more discharge to the break-in. Again, it can't hurt anything, but it does make the process take longer, especially if a 100mA rate is used for the "pre break-in" discharge.

Dave

 

[LloydV]

thanks, dave.

documented proof or not, your explanation is certainly plausible - with the only added "cost" being the extra time to discharge.

 

[rivertonch44]

B) I want them in my camera etc ready in 100% charge - not just 60% from manufacture

Is this the best practice for this? I mean charging must bee 100%?

 

[apagogeas]

I think the term "pre-charged" or "ready to use" does not really refer to the partial charge in the cell right out of the pack but overall on the ability of LSD to maintain the charge over its whole useful life. Having this 60-75% initial charge is just a side effect of the need to have it partially charged by the factory to avoid quicker degradation whilst the battery waits at the stores for months. In fact, I believe if the batteries where uncharged or fully charged at the factory, the battery would suffer further degradation and the manufacturers try to avoid this as much as possible so to have more vibrant/healthy cells till the first use - no company wants more complains for a poorly performing battery right out of the pack. Of course, the need to do that partial charge is a convenient way to advertize it as a benefit too like "grab it and use it right away" instead of "if we don't partially charge it, the battery will degrade quicker"! We really don't buy an LSD for its initial partial charge anyway although if at need we can use it right away because of this side effect.