For about $10 more, also see La Crosse Technology's BC700. It can do some neat things like measure the capacity that was charged or run a "refresh" cycle that repeatedly drains and charges a battery (up to 20 times) until the measured capacity stops increasing.

Like the BQ-CC55, it has four independent channels that can charge either AA or AAA in any mix. You can even run different modes on each channel, like charging 1 and 2 while refreshing 3 and 4.

Ha! You beat me on making that recommendation. I have used a BC700 for about two years now, and am very satisfied with it.

I particularly appreciate how each of the four battery slots is separate. Not only does that mean each battery can be doing something different (charging, refreshing, etc.), it also means you can remove and insert different batteries at different times. This is great when some batteries are more (or less) discharged than others.

Also, worth noting that the BC700 supports NiCd and NiMH, in addition to AA and AAA.

I've had the BC700 (or possibly one of the identical builds under a different brand name) for years, but switched to the BQ-CC55.

The latter is "put in and forget". The former means fiddling with really bad buttons (because you can! Not really because you have to. But if I can manually set and micro-optimize the charging current, by God I will).

I worry much less about charging nowadays.

I can't say I've used the custom charging current options, but the refresh mode has rescued some batteries that (very unscientifically) did not seem to be holding much charge.

IIRC the default behavior is to charge at 200 mA and discharge at 100 mA.

These are great but toward the end of the charge cycle they make a lot of high-pitched sounds.