I am doing some break-in charging of A size NiMH cells.
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cycles fail to terminate with -dV set at 3mV and Temp goes up to about 40C-45C but does not trigger end of charge.
I remember -dV (negative delta V) being the end of charging criteria for CdNi, while for NiMH the charging is considered completed at 0dV (zero delta V).
If possible, set the charger to stop at -dV = 0mV for NiMH.
Even so, after many cycles in a battery the dV detection might become unreliable. That usually happens after 1-2 years of usage for my AA/AAA. Still good to use for a couple more years but for low current loads only, and charger will overheat them until the timeout occurs. That is why I charge the old batteries with a slow charger that ignores the voltage and it just pumps the same current for 16 hours straight.
An alternative way to detect when an old battery is full (while still using fast charging) could be the sudden raise in temperature. When the battery can not store any more energy into its chemistry reactions, most of the energy pumped by the charger will have to go somewhere, so it will transform into heat and thus will appear a sudden raise in the battery's temperature.