BTW i'd like to see the data sheet on the NiCd's where they state the 5 year life spec, thanks for mentioning that.
Here is the datasheet, its nicd, which have huge amounts of test data for emergency use, because theyve been used for it for years.
Nimh datasheets never give lifetime in years, -but always in number charge/discharge cycles, which is irrelevant for emergency use which will have few charge/discharge cycles over time.
The first thing the customer asks when they want an emergency lighting battery is "how long will the batteries last"?
With nimh datasheets, this question cannot be answered....with nicd datasheets , this question can be answered.
Its just not possible to sell a emergency light battery to an installation without being able to give them an idea of how long the battery will last.
With nicd, you can give them this data, with nimh , you cannot give them this data.....because "constantly topped up" nimh batteries dont have lifetime data........and low selff discharge nimh's are not likely to be emergency capable....and in any case, "low self discharge" still has a significant self discharge, its nowhere near zero.............of course, most , if not all nimh datasheets dont even state what the self discharge is, so its a non-runner
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