AA Eneloop gone all NULL on me!?!

[D-an-W]

One of my AA Eneloops (Purchased August last year) is tonight refusing to charge in my TechnoLine BC-900, the display just remains at null regardless of what port I try it in. The other Eneloops are charging fine (So far) so I am pretty sure it's not the charger.

Is there anything I can do to kick start it back to life or if not having bought them from 7dayshop.com should they replace it for me (UK based)?

TIA for any advice you folks can offer...

 

[Mr Happy]

What is the history of the cell? What was it doing (or being done to) before this happened to it? Do you have a voltmeter to measure the voltage on it?

It could be the voltage is too low, which is A Bad Thing. You could perk it up by charging it briefly from another good cell (connect them in parallel, + to +, − to −).

 

[Apollo Cree]

If you've got a dumb slow trickle charger, give that a try. Sometimes the smart chargers will refuse to play with a battery below a certain voltage.

 

[D-an-W]

It was in a Wiimote, I will go measure the voltage now...brb

Damn I love you guys (In a man way of course :kiss, just a few seconds bridged across a freshly charged AA and it's charging again!


What's the optimum charging current for these AA Eneloops and also some AA TechnoLine 2700's (that came with the charger) please?


lovecpf

 

[Magic Matt]

Wiimotes are calibrated to Alkaline cells, not NiMH. I swap my rechargables out when the Wiimote says it's on the last bar, BEFORE it screams at me to change the batteries. If I leave them until the Wii screams at me, very often they are below 1V when tested, whereas on the last bar they are just over (usually around 1.05V to 1.1V). I'm currently using the Duracell 2650mAh cells in my Wiimotes until I get the C9000 as the Duracell charger seems a bit potent for the eneloops (charging at 1.3C) and I don't want to damage them.

 

[D-an-W]

I try and rotate the Wiimotes so they get even usage but I guess this one must have been left in the guitar a bit longer than was good for the batteries!

 

[Black Rose]

I'm usually very proactive about checking the cells in our Wiimotes, but with the overtime I've been working lately, I forgot all about them....

2 pairs of cells would not even register on the Wii remotes "power bar".

I checked the voltages and they all were below 1.0v, one was down to 0.32v

My C9000 did not reject them and they are now undergoing a Refresh and Analzye cycle to see what damage has been done to them.

 

[Magic Matt]

Well I've just got 1400mAh out of a 1800mAh cell that was down to 0.1V so I wouldn't count them out yet, and that was just one Break In.

 

[mfm]

What's the optimum charging current for these AA Eneloops

1C (2000 mA).

 

[Mr Happy]

What's the optimum charging current for these AA Eneloops and also some AA TechnoLine 2700's (that came with the charger) please?

1C (2000 mA).

1C is about the absolute max. You should use the lowest charging current that produces reliable termination. Start out at 800-1000 mA for AA eneloops and work up from there if that is unsuccessful. Higher charging currents will reduce the working life of the cell (higher temperatures, more wear and tear on the recombination catalyst at the termination point when using −∆V termination).

 

[Magic Matt]

I thought they recommend 0.1C for a slow 16 hour charge, and between 0.5C and 1C for a regular charge on the eneloops... wouldn't 800mA be a little low at 0.4C?

 

[mfm]

I thought they recommend 0.1C for a slow 16 hour charge, and between 0.5C and 1C for a regular charge on the eneloops... wouldn't 800mA be a little low at 0.4C?

You are correct.

You should use the lowest charging current that produces reliable termination.

Not really, but at 1000 mA or higher he will be OK.

 

[Mr Happy]

I thought they recommend 0.1C for a slow 16 hour charge, and between 0.5C and 1C for a regular charge on the eneloops... wouldn't 800mA be a little low at 0.4C?

This 0.5 - 1C thing is one of those little pieces of advice that seems to have taken on a life of its own and become detached from the reasoning behind it. There is nothing magic about the 0.5C number. Some sources will say 0.33C.

We must remember that the goal is to produce reliable termination and the charging current is a factor in that objective. However the specific design, quality and life history of the cell is a factor as well. With Eneloops specifically many factors come together to produce reliable termination signals at lower charging currents, and where they work, lower charging currents are advisable.

You can charge Eneloops at 1C and they accommodate that better than many cells. Whether you should charge at 1C is another matter.

 

[45/70]

This 0.5 - 1C thing is one of those little pieces of advice that seems to have taken on a life of its own and become detached from the reasoning behind it. There is nothing magic about the 0.5C number.......

I think this is partly true. The way I see it though, is a 0.5-1C charge rate can be used to charge any NiMH/NiCd battery, whether LSD or not, with any reasonable charger with that capability.

Now, if you want to cater to 5 different brands, some LSD, some not, with 5 different charge rates, customized for their specific behavior, that's fine, but provided all of the cells are in reasonably good heath, the 0.5-1C charge rate will work. It's a simpler formula, "Plug and Play".

Dave

 

[zipplet]

I have found the 700mA setting on the BC-900 to be a good compromise for eneloops. They always terminate reliably for me at that setting.

 

[Black Rose]

An updated on post #7.

I took the 4 cells out of the C9000 after the discharge portion of the R&A cycle.

The capacities reported for 1000 mA charge, 500 mA discharge are:
1882 1902 1889 1883

I now have them on a break-in cycle to see what numbers are reported compared to my previous break-in numbers.

 

[SilverFox]

Hello Mr Happy,

Keep in mind that the recommended charging rate of 0.5C - 1.0C is coming from the battery manufacturers as a charging rate that will create a strong end of charge signal over the life of the cell.

With new cells, you can often charge at reduced rates and get proper termination, but as the cell ages the -dV signal gets weaker. One of the advantages of 1C charging is that the higher charging rate elevates the cell voltage. If the end of charge signal is missed, the cell will usually terminate on high voltage.

Of course, once a cell is totally crap, its high voltage will cause termination regardless of the charging rate. I have been playing with a couple of Tenergy 2300 mAh cells that have turned to crap. After totally draining them to an open circuit voltage of 0.7 volts, I put them on a 0.1C charge and the voltage immediately went to 2.1 volts. They actually get "toasty" when charged at 500 mA.

I find it interesting that they will run a single cell single LED solar light for less time than the 600 mAh NiCd cells that came with the lights. Truly crap, even in a extremely light load application.

Tom

 

[Magic Matt]

There is nothing magic about the 0.5C number. Some sources will say 0.33C.

Thanks for the extra information. I just thought the quoted 0.5C, 1C etc. was provided by the manufacturer, and varied simply because the battery one manufacturer produces may have different charging requirements to another. I hadn't fully appreciated the reasoning!

I charge my eneloops at 0.5C,simply because a 2 hour (ish) charge fits in with my schedule quite well.

 

[Black Rose]

The break-in on my < 1.0v Hybrids has completed.

That cell that was at 0.32v cell has taken a hit.
It went from 1944 mAh to 1887 mAh capacity.

The rest fared better, and one even increased in capacity :thinking:

 

[45/70]

It would be interesting, Black, to see how that cell does a few cycles from now, and whether the "gap' widens, or stays the same, compared to the other cells.

Dave