I can't comment on Nikon flashes but my experience with energizer rechargeable are that they are inconsistent at best. They don't hold a charge very well and they have a inconsistent discharge cycle leaving you with a different charge level in each battery.
Invest in some Maha Power Ex 2700mAh or Sanyo 2700 mAh rechargeables. My favorites are the low discharge Sanyo Eneloop or Maha Imedeon. These are great for long term storage while maintaining a charge.
Also invest in a good maha battery charger to take advantage of the performance of these batteries and to maintain their longevity and consistent charge levels.
Thomas Distributing