Hello Bart,
I entirely agree. I have been using a BL-700 charger since buying a set of eneloops for my Pentax K-x about 6 months ago. The spec declares that it has -dV and overheat detection.
The BL-700 switches to "fully charged" when a cell voltage reaches 1.49 to 1.50, at which point the cells are warm but not hot (200 mA charging current). I choose to end the charge for all cells at the point when just one cell displays "Full", rather than trying to squeeze another 0.02 volt into the remainder (the charger is normally sitting on my desk where I can glance at it from time to time).
One thing that I am uneasy about, even with this good smart charger, is that the charge continues, at 5% of the initial current, when the cell has reached "Full". This, of course, is a hangover from the old Nickel-Cadmium (Nicad or NiCd) cells, where a trickle charge of C/20 was recommended. From what I have read, trickle charging a full NiMH cell is not recommended, and may cause some over-charge damage. I'm no expert on this; it's just what I remember reading somewhere.
My over-cautious attitude dates from my first (and only) mobile/cell phone, which I bought in 2001. It uses AAA-Long NiMH cells. The instructions told me to fully charge overnight, rest and then give the cells another full charge. I think that the instructions had not been re-written since the manufacturer (Motorola) probably switched to NiMH from Nicads. This treatment effectively destroyed the cells within a month! When I took them out they were brown and bulgy! They were a non-standard size, about 6 mm longer than AAA cells. I bought some standard cells, soldered a 6 mm brass extension on their ends, never charged the phone for longer than 45 minutes, and it's still working fine, some 10 years later, with only one further change of AAA NiMH cells. We are a frugal household, and don't give a damn if our phone is laughably ancient.
Cheers,
Martin
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