Those that do the slow over night charge on NiCad or NiMh are usually rewarded with a much longer battery life (more charge/discharge cycles) than those fast charge. While fast charge is convenient for those impatient ones, it is always hard on the batteries. Eneloops should not be fast charged ever. You will find that the Eneloops will provide the most reliable and long term life than any of the other batteries for use in transmitters. They hold a charge as well as LiPo's and will not be destroyed if you discharge them to deeply.