Problems with IKEA LADDA 900mAh AAA batteries

[SigmaTheDJ]

HI,

I've been using IKEA LADDA batteries for around 3 years now. I am having an issue with the AAA versions. They're the white 900mAh ones, which I believe are discontinued now.

I'm using an XTAR VP4 Plus Dragon charger. When I try and charge LADDA AAAs, what often happens is either the charger will say a battery is fully charged after just a few minutes on charge, or it will just keep charging a battery forever and it never stops automatically, which can lead to it getting quite hot. If it says the battery is fully charged prematurely, if I take it out and put it back in again, it will start to charge again. Sometimes I have to do that a few times and eventually it will fully charge. I'm charging at 0.5A, which is the lowest my charger goes.

I'm having no issues with my AA LADDAs. Just the AAAs.

Rechargeable AAAs are only cheap, so replacing them is obviously no problem, but I'm just wondering if what I'm seeing is a sign of the batteries reaching their end of life, or whether something else is happening, e.g. a faulty charger.

Thanks for any insight you can give.

 

[chillinn]

which can lead to it getting quite hot.

There are a few things that can damage a cell, which increases internal resistance in the cell, reduces capacity and current output. Overcharging is one way, slamming a full cell with current or voltage will cause it to heat up, and heat damages a cell. A smart charger should be able to mitigate any overcharging, as long as you're not charging at too low a current, as this can lead to missing termination because the cell will heat up too slowly as capacity becomes full. dV/dT is how smart chargers determine charge termination, so it needs to see a rapid increase in temperature to know to terminate charge.

Overdischarging is another way. With NiMH, discharging below 0.9V will increase internal resistance. Not allowing freshly depleted and still warm cells to cool down before charging, and using cells hot off the charger with no cool down rest period, are other ways to damage a cell and increase internal resistance. Dropping cells on hard surfaces will also damage a cell, increasing internal resistance, leading to noticeably poor performance.

Those IKEA LADDA AAA 900mAh, and if your LADDA AA are 1900mAh or 2450mAh, then they are actually rewrapped Eneloop cells made in Japan at FDK Corporation. The strong consensus here is that Eneloop are the best LSD NiMH cells available.

Eneloop can tolerate and prefer a little more current charging. AAA cells are small, though, so want less current. So charging AAA Eneloop around 1/2 C, or for those 900mAh cells, around 450mA, will help prevent a smart charger from missing termination. I charge my Eneloop AAA at 475mA.

Eneloop AA 1900mAh and Eneloop Pro AA 2500mAh are larger cells so can tolerate and prefer a lot more charge current. Charging at 1C (1.9A) or 2C (3.8A) is far better than charging slowly at 150mAh (around 1/12th C). My older D4 charger only goes up to 750mA, so that is what I charge my Eneloop AA at, but 1A would likely be better.

If your charger is not smart, but dumb and based on timed charges of 8 hours @150mAh or something, that's you're problem. Get rid of it and replace with a smart charger.

 

[SigmaTheDJ]

If your charger is not smart, but dumb and based on timed charges of 8 hours @150mAh or something, that's you're problem. Get rid of it and replace with a smart charger.

Thanks very much for your reply. My charger is a smart charger that is supposedly very good, although it only has 3 selectable charging rates: 0.5A, 1A, and 2A. I use 0.5A for AAAs.

The charger has worked fine for several years, including with AAAs, so it's only recently that I'm having issues and only with these LADDA AAAs, not any AAs, 18650s, or 21700s that I charge, so I wonder if the batteries are just worn out.

 

[chillinn]

Is it possible any of the other reasons I listed occurred? Ever run your cells to empty? Before I learned best practices from CPF, I probably murdered about 32 NiMH cells in the first 3 years, AAA and AA mixed, with overdischarge, then overcharge on a dumb charger. But since I got a smart charger and adopted best practices 6 years ago, I haven't lost a cell since, except for a very few Liion I accidentally deeply over-discharged for too long by falling asleep.

 

[louie]

I've used the Xtar Dragon for years with Eneloop AA and AAA and have no problems, using 1A for AA, and 0.5A for AAA. In fact, the Xtar is quite good at charging marginal cells that the Maha 9000 rejects. So, I would guess that the cells are no good.

You might try using the Xtar's internal resistance probes and compare to new cells.

Xtar review:

Review of Charger Xtar VP4 Plus Dragon

 

[Christoph]

May even try excersizing them do some refresh cycles on them. Dragon is a decent charger.

 

[SigmaTheDJ]

Is it possible any of the other reasons I listed occurred? Ever run your cells to empty?

They are mostly used in a pair of wireless Sennheiser headphones. They beep when the batteries are running low, so at that point I just swap them out for some freshly charged ones. I've been doing that for years though.

But yeah, I can't think of anything that I've started doing differently that might have caused this.

Thanks for the other replies too! I thought about testing them using the probes, but I can't remember where I put them. I bought some 1,100mAh EBL AAAs today, so I'm gonna see how I get on with those and if they have the same issue.

 

[hamhanded]

you're not charging at too low a current, as this can lead to missing termination because the cell will heat up too slowly as capacity becomes full. dV/dT is how smart chargers determine charge termination, so it needs to see a rapid increase in temperature to know to terminate charge.

Just a heads up, temp is not a factor in dV/dT charge regulation, thats voltage and time. Charge current does indeed affect the charge accuracy, though, because charging a cell too quickly can increase its internal resistance. And smart chargers may also have overtemp protection, even if it's mot strictly related to determining the state of the cell during charging.

 

[chillinn]

Just a heads up, temp is not a factor in dV/dT charge regulation, thats voltage and time.

Right, the voltage drops during a certain time during the charge.
-dV/dt is standard, but smart chargers sometimes also detect an increase in temperature when capacity is full, which would be dT/dt. Thanks for catching that.

 

[captianworkbench]

I have been absent from the forum for quite some time, and I do not intend to hijack the thread, but some comments on charging have me scratching my head.
Timed, low rate charging was said to be bad for the cells, and charging faster with a dV/dT and/or dT/dT detection was stated as better. I do not understand why charging at a C/10 to C/16 rate "overnight" would all of a sudden be bad for NiMh cells. Yes, you have to wait, but if the cells are not overheating then what would be the problem? I have had good luck and long life out of cells using this approach.

 

[chillinn]

have me scratching my head.

The comments were referring only to Eneloop. The higher current helps prevent them from missing termination. Charging Eneloop at low current, even in a smart charger, can and likely will cause them to miss charge termination. When this occurs, the cells will heat up and this occurs slow enough to undermine any dT/dt function the charger has, also they will be subject to overcharging. That's a double whammy, heat and overcharging, and damages the cells

Other non-FDK Corp manufactured NiMH may behave differently, but Eneloop, specifically Eneloop, prefer higher current charging specifically to avoid missing charge termination.

 

[NiOOH]

Just a heads up, temp is not a factor in dV/dT charge regulation, thats voltage and time.

Actually, the temperature increase at the end of charge is the reason we see a voltage drop with NiMH cells. Unlike simple conductors, NiMH cells have a negative temperature coefficient of resistance, i.e. the resistance decreases slightly with the increase of temperature. This causes -dV when the cell enters overcharge.
As I (and others) have written many times, -dV is not the ideal method for charging NiMH cells. The cell reaches 100% SOC at its peak voltage, i.e. the proper method for voltage termination is 0 dV or the so-called peak detection. Any voltage drop after this is indicative of overcharge. Unfortunately, there are not many chargers on the market today that use this method, mostly because it is more complicated (and expensive) to imlement.

 

[captianworkbench]

Ok, I get that. Charging at some higher rate but missing the EOC termination due to whatever reason would of course cause any cell to overheat and therefore be damaged. Some cells most definitely like some chargers better than others. Personally, I have had one charger tell me that a cell is bad, and not even start, where the other charger will charge the cell just fine. And I know the cell performs just fine. Some times you have to out-smart the "intelligent" charger.

 

[NiOOH]

Some chargers try to estimate the cell IR by applying short, high current pulses and measuring the voltage off the cell. Above certain value, the charger will not start. This is OK at preventing some really old or damaged NiMH cells that may not display the typical voltage characteristics during charge and may not terminate properly. However, setting this value too low may prevent some cells, that are still useful from charging. Getting a battery impedance tester may be very useful for tracking the cells IR and sorting them accordingly.

 

[hamhanded]

Some chargers try to estimate the cell IR by applying short, high current pulses and measuring the voltage off the cell. Above certain value, the charger will not start. This is OK at preventing some really old or damaged NiMH cells that may not display the typical voltage characteristics during charge and may not terminate properly. However, setting this value too low may prevent some cells, that are still useful from charging. Getting a battery impedance tester may be very useful for tracking the cells IR and sorting them accordingly.

Great information, thank you. Can you recommend any chargers that implement this properly? Is there a concise term for this proper implementation that I can look for?

 

[NiOOH]

The best way is to get a charger that doesn't have this pre-test and rejection routine at all, such as SkyRC MC3000. If you are interested of tracking your cells IR, a battery impedance meter is a very useful device.