AAs don't like high charge rates, they get hot and their life suffers. I charge mine at 0.5a with a peak setting of 3 - 5mv/cell. I've used both 4 cell holder and an 8 cell holder - still charge them the same way, 0.5amp.

0.5amp is considered a slow charge. You can fast charge them at 1amp, just watch how hot they're getting.