Originally Posted by
gecho
There are 3x AA to D cell adapters so you can run nimh rechargeables in D cell devices. Just be sure to get the parallel version that increases the mah, not the voltage. Though it can be a chore to recharge all those batteries. My parents have a 3 D cell LED lantern so I have 9AAs to charge in a 4 slot charger. The other day I saw an adapter that converts 4 D cells to a square lantern battery, so you could do adapters inside an adapter, but having to recharge 12 AAs whew. Most rechargeable D cells you might find are just a single AA inside an adapter, not at all useful (2100 mah vs 8800 mah alkalines) and difficult to find a chargers that can handle them.
NiMH have one huge drawback...they go to mush in cold weather. My bikes are all chained outside. Lost a really cool bullet light years ago in the winter to learn that. On the other hand I had 3 Sunbeam or Panasonic dollar store AAA's last six months once in a Bell 3 LED taillight, including during Snowmageddon in early 2017.
So no, there isn't any real savings there. What I've got is fine. And the NiMHs are for my digital camera.