I have been analyzing NiMh batteries, both in a pack of six and individually. To get right to the point, I have found that the batteries in a pack never last as long as those charged individually.
I had purchased an FNB-83xh 7.2V 2500mAh pack for my Yaesu/Vertex VX-150 a few years ago. During most of the life of this pack, I have been using the radio mainly for receiving (railroad band) and not doing much transmitting. So I have not been asking the batteries for much current, and the pack appeared to be working fine.
But over the past six months, the pack would not charge properly on the Yaesu CD-30 desktop (rapid) charger. This charger puts out 400mA, so this is not really a rapid charge - 400mA should be a decent (if not a bit on the low side) charging rate for the 2500mAh pack. The charger was reporting a fully charged pack after only half hour or so. After removing the pack and re-inserting it into the charger, it would charge another hour or so.
When I transmitted on the VX-150 with this pack, the voltage would drop from 8.0 to 5.8V immediately. This was on a supposedly fully charged pack. So I knew that there were a couple of dead cells in the pack.
I decided to cut the pack open and separate the batteries. I found that three of the batteries were labeled Sanyon 2500mAh, with the part number HR-3U. The other three batteries were not labeled.
When I inserted the batteries into my bran-new Maha MH-C9000 charger/conditioner, on the "Refresh/Analyze" mode, four of the batteries failed almost immediately with the "HIGH" reading. This indicates that either the battery is open, and will not take a charge, or it is not a rechargeable battery. It is a feature the charger has to prevent attempting to charge alkaline and other non-rechargeable batteries.
The next step was to discharge the batteries without charging, using the "Discharge" mode on the C9000. The result was pretty much the same, except that the report wasn't HIGH, but the charger reported "Done" after only a few minutes on the discharge cycle.
I was able to get the remaining two batteries from the pack to run on the Refresh/Analyze cycle overnight, but when done, the capacity was less than half of the rated 2500mAh. So it is obvious that the entire battery pack was toast.
I have been using Eneloop batteries for all of my rechargeable battery needs, and am very happy with them. The latest version (Panasonic 3MCCA) have the same capacity (1900 min 2000 typ), but have a maximum cycles of 2100. The problem with these batteries is that the charger they came with charges two in a series, and this is not optimal. That is the reason I purchased the MH-C9000. I have learned a lot in just the week I have owned this charger.
For one thing, the Eneloop batteries come charged, but if you want to get the full capacity from them, you need to run them through a few cycles of charge/discharge/charge. Bran-new Eneloop (Panasonic 3MCCA) placed in the MH-C9000 on Refresh/Analyze (which first charges the battery full, rests for 1 hour, discharges, rests, then recharges), none of the bran-new batteries (I bought a 12-pack) reached their minimum capacity of 1900mAh. Most were very close (1800-1880), but two were significantly lower - 1789.
Older Eneloop (1st gen 3UTG) had lower capacity, most in the 1700-1800 range, but one or two were as low as 1360. These older batteries had been recharged exclusively in the Eneloop NC-MQN06U - 300mA, which charges four batteries in sets of two.
I also have an Eneloop NC-MDR02NU 2-cell charger that will charge AA batteries individually at 550mA, but I used that charger mostly for AAA batteries.
I have been researching NiMh batteries over the past few weeks, and from what I have gleaned, I can safely say that batteries in a series pack cannot be properly charged.
In addition, batteries must be selected to have capacity within 5% of each other in order to get the best performance from the set in a pack.
For this and other reasons, I have resorted to using the AA cell trays for my VX-150 and FT-530, and have built a pack of 10 AA for the FT-530 (requires 12V to produce 5W output) in which I will be using Eneloop AA cells and charging them exclusively on the Maha MH-C9000, following recommended procedures.
Eventually I may switch to Lithium battery packs, but until then I believe that individually charging/conditioning the Eneloop AA cells and selecting them for capacity within 5% to place in the AA cell holder will result in optimal performance and life.
It is unfortunate that our radio technology has advanced in leaps and bounds, while battery technology is still in the "dark ages" of technology.
I believe that within the next few years, more advanced battery technology will be available, giving us much better performance from our portable equipment. But as is always the case, new technology must go through a period of trial and error before it is perfected, and is reasonably priced.
Lastly, I want to warn you that rapid charging of any NiMh or NiCd battery will ruin it. The recommended charge rate varies depending on the battery. Here is an excellent thread on Eneloop and other NiMh batteries in the CandlePower forum. Please note that the reference to "C" as in 1C, 0.5C, etc has nothing to do with temperature. "C" referrs to capacity of the battery. Charge rates are in fractions of C.http://www.candlepowerforums.com/vb/showthread.php?190625-Eneloop-Charging-Rate
Frank - KE2KB