Loading very fast

This charger does what it says: it loads very quickly (15 minutes for 75% charge) 1, 2, 3 or 4 AA or AAA batteries. There is an LED for each stack location: red (charging), flashing green (75% load), solid green (100%), flashing red (battery not accepted / there is a problem). Charging is done with a little fan noise, nothing too serious, and as soon as the batteries are charged, the noise stops automatically. Sometimes it does not recognize a stack and then the LED flashes red. So you still have to keep an eye on, hence the star less.
The charger comes with 4 AA Duracell 1300 mAh NiMH.