OP
archae86
•
Contributing Member
•
Posts: 658
Re: Thanks and some OT questions
Mark K
wrote:
archae86
I am currently using Maha c801D charger
1. I have some 40 Sanyo 2500mAh, 4 Energizer 2500mA, 12 Sanyo 2300mA,
and 4 GP 2700mA AA batteries. I have been puzzled by their almost
instant discharge property. Question
a. Will there be any chance I bought fake NiMH batteries or
b. Is the the universal physical property of NiMh batteries or
c. The chemicals inside are exhausting
I don't have a full picture of your situation, but it seems to me that the two most likely issues are either:
1. your usage pattern has simply consumed much of the useful lifetime of many of your batteries. It is typical of batteries with appreciable usage to lose both capacity and retention lifetime. Manufacturer's claims of 500 or 1000 cycles should be viewed with much skepticism, as they generally assume benign use conditions, and allow very considerable loss of capacity.
I've not kept formal cycle counts on my batteries, but would hazard a guess that in general my NiMH batteries have ceased to be of good use to me after perhaps a hundred cycles, and sometimes far less.
If your usage style routinely runs a set to full depletion, then, depending on the device, it probably drives at least one cell in the set to reverse voltage. In that case the cycle life is likely to be far, far less than 100. You might get considerably better lifetime out of newly purchased batteries if you can find a way to avoid running the set down so far (maybe charge every night, or, if the device has a battery meter, change out the set at a higher reading than has been your practice).
or:
2. your charger is terminating charge too soon on many of your batteries.
This second point is far from impossible, in fact none of the "smart" chargers I've owned with the possible exception of my Maha Powerex MH-C8000 have been entirely free of this fault. If you have a simple "stupid" charger--the sort which does not sense the voltage on the batteries at all, but just charges at something like 0.1C forever, or possibly something like 0.2C for a time limit of 5 to 10 hours, then you can try charging the same battery on the stupid charger. If it gives substantially better service, then your c801D terminated prematurely on that battery (it tries to sense the negative delta-V point, and sensing that can be a problem--which may be as much the fault of the battery or of your usage as of the charger).
As my experiments did not explore cycle life, I have no basis in my own data to recommend the low self-discharge units for your situation. Nevertheless, I think you'll probably find them better in your service. As I imagine you have heard, it is well to keep the batteries in sets--this makes it less likely that a mismatched battery will get prematurely destroyed by reverse voltage in service.
-- hide signature --
new 350D user July 1, 2005