I may be mistaken, but I think that the temp sensor in Nickel chemistry
batteries is there because it's the easiest,
cheapest way to tell the charger when to shut off.
What they do is assume that if the battery is heating up then it must be
full, so they shut off the charger. That's
why you don't get very many cycles from your cordless tools batteries.
Constantly overcharging Nickel cells shorten
their life. But a proper charge algorithm would add cost to the tools, and
we Americans are generally penny wise and
pound foolish and would gladly pay less up front and replace the battery
pack three times as often.
Everthing I've read, generally "sums up" that Nickel or even Lithium
chemistries want to be left in a state of
discharge for maximum cycle life, just the opposite of lead chemistries.