Liitokala Lii-500 doesn't terminate on NiMH Batteries?

Hi All,
I just received my Lii-500 and decided to test some of my rechargeable batteries. For 18650 it seems to be working fine. It also seemed to have worked fine on first few AA NiMH batteries.
Then I have noticed that it took too long to start discharge in normal test mode. The display was showing 1.5V, but when I measured the voltage across the terminals it was 2.2V. I have tried a different cell, that have been tested OK already - same thing, the voltage display would stop at 1.5V but the voltage across terminals would keep climbing.
I have tried different slots and different cells (AA, AAA, eneloop, LADDA), all with the same result, both in test and charge modes. Only the newest cells, that I purchased a few weeks ago, charge fine. Some of the ones that I am having trouble with are fairly old, but some are maybe a year old with only a few cycles.
Is anyone familiar with this issue?

I did not have any issue with my Lii-500. I charged AAA, AA NiMH cells with it without any issue. I don’t recall trying the normal test mode on those cells though. Some of the cells I charged were more than 10 years old and some were new stock high capacity ones.

Are you using the power adapter provided with the unit?

I am using 12V 2A power adaptor from external HDD. The original on is 12V 1A IIRC, so it shouldn’t be the problem. I may try with the original one just in case.

I had similar issues on several chargers, with some cells, others worked fine. My theory is, deltaV that chargers need to sense in order to terminate charge may not be in the range that chargers are programmed to see. or not as well defined, it could be floating, as the cell racks up cycles. 2.2v is definitely not supposed to happen, hot off the charger nimh should be 1.5-1.6v. Are you measuring voltage with the cell in your charger, or is it out of the charger?

I use simple wall ac/dc adapters of proper voltage and current, to charge cells that would not charge in smart chargers. I time the charge, about 140% of capacity seems to work fine, and charge them fully.

Correction - original charger is 2A, I was using it with 3A. Anyway, switching to original charger didn’t do anything.
The voltage I am measuring is while the battery is in the charger.
I have contacted the seller and they told me they’ll forward my problem to their engineer. We’ll see what they say.

Then you are not greeting actual battery voltage.

with 99.9% probability i can predict their answer, "it is your battery, our chargers work properly and we had no such complaints before". or something along those lines.

What current are you using? You might need higher for the charger to more easily know when to stop:

“It`s better not to charge at a very low current because it is more difficult for the charger to recognize if a battery is full.”
“An Eneloop technician actually recommended charging with .5C - 1C.”

That means 1000mA (one amp) would be a good current for AA size, and 500mA for AAAs.

I am measuring the charging voltage. Even if the cell hasn’t reached it’s maximum voltage I don’t think it’s safe/healthy subjecting it to 2V.

I am charging at 500mA. Even if fails to detect termination, there should be some safety cutoff voltage, not going all the way to 2V

You are not be reading actual battery voltage, you are measuring voltage of entire charging circuit, with the cell being in series with it.

Let me explain with real world personal example, nyc mta transit rail system runs on 600v between track rails and the third rail, tunnel crew uses special made light to illuminate their area of work, which is nothing more than a wooden board with 5 120v bulbs mounted and wired in series, they use clamps to hook it to track rail and a third rail, 600 divided by 5 is 120, so each bulb gets 120v and happily works quite some time, However if you take a voltmeter, and measure voltage across terminals of 1 bulb, you will see 600v, not 120. so how come 120v bulb does not burn out, with 600v across its terminals? honestly i do not know, but i know this is how it is, I tried it myself at mta school. So imo you have identical situation, and your cell does not actually see 2v as you dmm suggests.

To have 0.6V voltage drop from 2.2V on the terminals to 1.6V inside the cell, it must have resistance of 1.2ohm, which doesn’t seem reasonable to me.
(Assuming cutoff voltage for NiHM battery of 1.6V on the cell itself and that the charger maintains constant 0.5A charging current until cutoff)
Also, the charger’s voltage display matches my DMM fairly closely until it reaches 1.5V. Then the charger value remains roughly the same, yet voltage reading on my DMM keeps going up.
Based on this, my guess is that for some reason the charger decides that it is charging a Li-Ion battery, and tries to bring the voltage it up, while the battery just isn’t capable of going any higher, so it stays at 1.5V.

I have a same case with my liitokala 500.
Good NiMH cells with low internal resistance are charging good without heating. Problem is with old worn cells with high internal resistance which can’t terminated charge and I measure about 2.2 volts on them when they are in charger.They get very hot, I measure 45-50 dg celsius. I try to conect that worn cells on laboratory dc power supply and rise voltage slowly to see how much current they can pull and I see that currents are very small, for example, I put 3 volts 2000mah AA NiMH and get current about 600 ma. With good cell it will pull 4-5 amps with this ‘high’ voltage.
That worn cells I charge in liitokala 500 with 300ma current and I terminate charge with timer on power supply and only use that cells for radio receivers which has small current consumption and they are good for that usage.
With lithium cells I don’t have problem with this charger but sometimes laptop pull cells can get hot when charge and termination is longer than it would be and I discard that cells imediately.

I charge these same cells with Nitecore I2 without any problems. They get warm, but not too hot and it terminates just fine.

I just charged my 10+ year old (produced 2006) Eneloop with my Lii-500.

The internal resistance of the cell was measured 250mOhm on YR1035, but it showed 45mOhm on Lii-500. The internal resistance measured on my current charger Lii-600 gave me numbers that are similar to that from YR1035.

The cell was stored fully charged not long ago and it took about 20 minutes before Lii-500 stopped charging. The displayed voltage did not go over 1.5V and terminated around 1.48V. When I checked the voltage across the charging pads a few minutes before it ended, the measurement did not go over 1.65V.

I recently learned that internal resistance of NiMH cells tend to shoot up exponentially as they age. Thanks to the recent post by thefreeman I came across a very interesting website that shows how NiMH cells age. See http://aacycler.com/ According to the webpage, the way cells age varies alot. It could be possible that your cell has very high internal resistance.

By the way, my Lii-500 is almost ten years old. So, the charging logic may have changed since.

I’ve had 3x Lii-500 (not S). Still have one. OK charger but the IR feature for NiXX is useless. Measures 45 no matter what NiXX is in it. Seems to work more properly with Lion. No idea what the issue is there.
I have not had a noticeable problem with NiMh charging and I have some pretty old cells with high IR. Sometimes it’s a matter of setting the charge rate to deal with the IR. Sometimes ‘some’ cells do better in other chargers.
If IR gets too high, and termination/heating become a chronic issue I recycle the cell. Usually by then they are pretty used up even for low draw applications.

What kind of meter?
The harbor freight and others of that family are wildly inaccurate when run on a low battery.
Charger shouldnt push a cell much over 1.5v.
In fact that is how they reject alkaleaks.

It’s Chinese “B-Side” multimeter. It is fairly accurate, it is also pretty much in agreement with Liitokala on voltages, other than NiMH batteries at the end of charge cycle.
Seems to me like it isn’t very good at detecting when to terminate. Nitecore charger terminates in less than a minute if a put charged battery in it. It takes few minutes with Liitokala.
I got a reply from the seller, they quoted Ohm’s law and explained high voltage by internal resisrance. Quote “Don’t worry, we are professional” :smiley:
Anyway, I won’t bother looking into it any further. Other than extreme case of one of the older batteries it works OKish with the rest.