Thanks for the links hertzian!
And thanks for the confirmation on my part number selection pro92b.
I've been messing with 4 Kodak branded 2500 mAh NiMH AA cells that I obtained somewhere or with something that I don't recall.
They may have been included with a Kodak digital cam the more I think about this.
I think they are only about a year old at the most.
I ran them through a refresh/analyze test on both a Maha C9000 and the La Crosse BC-700.
Both chargers said they were fine and rated them about 2100 on all four cells. I even ran them through a break-in charge in the Maha.
I used lower current settings for the charge and discharge settings depending on the charge setting I was using.
Anyway, I had charged them and put them into a Uniden HP-1 the other day.
Within about 20 minutes, the HP1 started beeping at me telling me the battery power was too low for audio recording and something else. I ok'd out of that and let it scan.
It only ran about another 20 minutes before squawking at me again but this time it said it was shutting down as the power was insufficient for anything. Something along those lines anyway.
I figured just one call had failed but when I yanked them out and measured them with no load, they all showed right at 1.00 volts +/- .05.
So I though I had maybe mistaken which set I charged and charged them again. Sure enough, the Maha showed them as having a capacity about 2100 just like before.
I used a little higher charge rate for that charge but nothing excessive.
Stuck them back in the HP1 and same thing, low power for audio recording after just 15 minutes or so.
This time, I opened the hatch before they could not power the HP1 and measured all four under its load. All four cells were quickly dropping towards 1.00 volts again. I barely had time to measure them all before they were too low to operate the HP1.
That is when I ran them through several recycle type charges in both chargers. Each time, the chargers would both show them about 2100 capacity when finished.
They sure as heck will not run the HP1 for more than 30 minutes tops.
It has puzzled me as to why both chargers report them as good. They seem to hold their charge well when the chargers are in the discharge state also. I mean, compare the time it takes for the Maha to discharge them at say a 500 mAh discharge rate to a set of similar capacity cells and the time is about the same. Stick them in the HP-1 though and they die fast.
The set of cells I compared the discharge time with in the Maha have been running the HP-1 for about seven hours now.
It's the weirdest thing I've seen since using these better chargers which I've had for a pretty long time now.
I gave up on the Kodak cells and tossed them as something is obviously wrong with them. Why the Maha and La Crosse chargers both said all four cells were good after several different types of charge cycles is a mystery that I guess I'll never answer. It takes such a long time to run them through a refresh cycle that it was no longer worth messing with them. Especially after they would discharge to around 1 volt in the HP1 within 30 minutes after all the refresh charges, break-in charges etc. that I did.
It was almost like these cells had a 1.00 volt design voltage which I know is not true. They never became warmer than normal during any of my different charge methods either so who knows what was up with them.
I did try them in a PSR500 and they died a fast death in that radio also.
Anyone ever seen a Maha or La Crosse show four good cells like that but the cells deplete super fast?
All my other sets of older NiMH cells charge up and show a capacity between 1800 and 2000 when finished charging and they do run the radios for hours as they should.
The Kodak cells are labeled "Kodak Rechargeable Digital Camera battery"
They show an "Up to 2500 mAh" rating and had a part number of "Ni-MH AA HR6" and are stamped with "1.2 volts".
They do not say who really made them and only say "Made in Japan for Eastman Kodak Company".
Whatever they are, they are junk! I bet I've only used them a dozen or two times in the year I've had them.
I only ever charged them when needed in the Maha charger until the other day when I discovered this odd problem. Since I found the odd problem the other day, I bet I've tried renewing them and normal charging them at least 12 times using both chargers but had the same poor results when put into a radio.
On the Maha charger, I tried every charge method that charger offers but same thing each time.
The last attempt, I cooked them by setting the charge and discharge currents high thinking maybe they really are made for a high current camera. That did not make them last any longer in the HP1 but they sure did kick out some heat during the discharge and charge stages. I think I set them for a 1000 mAh discharge and 1700 mAh charge rate. I was no longer trying to save them at that point and only wanted to see what they would do with the high current settings. It did not make them any worse but it did not help them any either. It sure did make me quit wasting time on them though!
The odd thing was when I did a comparison analyze/refresh charge test with a set of 2500 mAh rated cells (Nuon - cheapo Batteries Plus cells) in the Maha charger. Both the Nuon cells and the Kodak cells took almost exactly the same amount of time to complete the discharge/charge cycles in the Maha charger under identical charge settings and starting from a fully charged cell.
I really expected the Kodak cells to finish the cycle much faster than the Nuon cells being as the Kodak's seem to have no capacity when placed in a radio and a load applied. But nope, the charge cycles both took the same amount of time to complete.
I assume the Maha actually watches the battery voltage and that is how it terminates a cycle when it sees the cells voltage drop low for the discharge part of the test and the same for terminating the charge cycle when the cell voltage reaches its upper limit.
I know this Maha charger does not simply time the charge cycle or does it?
No, I know it does not as sets of older cells will have some cells that finish faster then others when they are getting old and a cell is loosing capacity. Those older cells will finish faster than the cells that are still working like new. So it must measure the cells voltage otherwise all cells would complete a charge at the same time.
When I did the Nuon and Kodak tests, both brands finished showing a cell capacity right near 2100 mAh for all cells.
Oh well, I found it interesting that both chargers reported the Kodak cells as good yet they were not good.
Perhaps there is something in the La Crosse and the Maha that cannot truly test a cell and can cause the false reading I seemed to get each time I tried a charge on the Kodak cells. Like a false positive!
Oh well, it was kinda fun trying even though it took several days to do all the charge or recycle tests.
