I have an application that needs a rechargeable battery with a very long service life (5-10 years ideally) as replacement will be difficult. Something of the order of AA size. Actual capacity not too critical.. It will be trickle-changed very intermittently (very small wind generator), and will be used outdoors, so must survive -20 to +50, although impaired performance at extremes is acceptable, as is gradual capacity loss over time as we will probably over-specify the capacity by a significant margin.
We've provisionally discounted using Lithium ion/polymer due to their intolerance to even trickle-rate overcharging, as it would be hard to keep track of charge in & out in our application. We're looking at ni-cd and ni-mh, but I've only found one manufacturer (Varta) who quotes service lifetime data ( as opposed to number of cycles). Does anyone have any comments/experience in this area..? Will hi-temp rated cells last longer? Is Ni-Mh better than Ni-Cd? Any examples of real-world lifetime experience, good/bad makes ?