Mr Happy
Flashlight Enthusiast
I have not read any reports of self-discharge studies on Eneloops over a period of longer than 6 months or so, and I've been curious about storage times out to a year or longer.
Recently I bought some Eneloops that had a date stamp of 2006-08 on the package (were they getting rid of old stock and is that why they were cheap I wonder?) and I thought that was a good opportunity to see if they were still good after 15 months on the shelf.
I put four cells in the C9000 and discharged them right away to see what residual charge they still held. I measured an average of 1380 mAh (+/- 9). My understanding is that the cells were probably charged to about 75% at the factory (that would be somewhere between 1400-1500 mAh), so they have presumably lost only about 100 mAh in over a year of storage. Quite remarkable.
I also wondered about capacity loss through non-usage. Would the cells need some refresh cycles before they could perform to full capacity? I put them on a regular charge a couple of times and measured about 1890 mAh capacity, which seemed a little low compared to the 1950 mAh I have measured on other samples. So I put them through a C9000 break-in cycle, and the capacity increased to about 1935 mAh. I conclude there was some loss of capacity over time, but only a few percent.
Overall, I am thinking that Eneloops are quite robust cells in addition to their low self-discharge characteristics. I have heard it said that some NiMH cells would not take kindly at all to being stored for 2 years without use. Whereas on this evidence I expect that Eneloops would still have a quite usable charge on them and would perform almost to spec.
Recently I bought some Eneloops that had a date stamp of 2006-08 on the package (were they getting rid of old stock and is that why they were cheap I wonder?) and I thought that was a good opportunity to see if they were still good after 15 months on the shelf.
I put four cells in the C9000 and discharged them right away to see what residual charge they still held. I measured an average of 1380 mAh (+/- 9). My understanding is that the cells were probably charged to about 75% at the factory (that would be somewhere between 1400-1500 mAh), so they have presumably lost only about 100 mAh in over a year of storage. Quite remarkable.
I also wondered about capacity loss through non-usage. Would the cells need some refresh cycles before they could perform to full capacity? I put them on a regular charge a couple of times and measured about 1890 mAh capacity, which seemed a little low compared to the 1950 mAh I have measured on other samples. So I put them through a C9000 break-in cycle, and the capacity increased to about 1935 mAh. I conclude there was some loss of capacity over time, but only a few percent.
Overall, I am thinking that Eneloops are quite robust cells in addition to their low self-discharge characteristics. I have heard it said that some NiMH cells would not take kindly at all to being stored for 2 years without use. Whereas on this evidence I expect that Eneloops would still have a quite usable charge on them and would perform almost to spec.
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:thanks
to everybody)
