ORIGINAL: apalsson
I have a temp probe on my charger but never used them. I have a habit of touching all batteries I charge though to se if they get hot and don't recall ever noticing a change when I charge at 1A
I'm not familiar with John's charger at all though. Modern day chargers are so cheap ($25 - $50) that I tend to retire the old ones and get the ones with more features. I also notice that when I charge my batteries with 1A as a max current, the charger spends a lot of the charge time at lower rates.
I agree, if a battery gets hot while charging, it's not a good sign. The Eneloops have a rated 1,500 charge lifespan (obviously at normal rates) so even if there is a slight reduction in life span, they give you a pretty good value
Like you, my chargers also have temp probes. But like most modelers I never use them and I'm not sure I would know how to program the chargers for their correct use!
Another danger with Eneloops and probably the main reason Sanyo recommends temp monitoring during charge is their reduced voltage depression when full charge is reached. Many older chargers can't detect this tiny voltage change and will continue to charge forever making the batteries very warm..... read that hot! Don't ask my how I know this! Temp. monitoring therefore acts like a secondary line of defense against overcharge.
By the way, the pack I overcharged has been working well for over a year now and so far shows no signs of damage. Traditional high impedance NIMH cells would have been wiped out given the same treatment.