So far the only NP-F style battery I have tested that meets or exceeds the manufacturers rating is the NEEWER NW-F970. Rated at 6600mAh and tested at 7200mAh.

I have been asked if the battery could be used to power a flash, but, I have not used a NP-F style for a flash, but I do use two 26650 cells in series with a high current switching regulator to keep the voltage around 6vdc. This works well but keep in mind the SB flash was released in 1997, when the only AA batteries available were carbon zinc, alkaline and Ni-CD. Battery tech has advanced quite a bit in the last twenty four years. These are not high current draw batteries. The SB flash has no current regulation built in and will accept as much current as your supply has to offer. The flash will draw over six amps to recharge the flash caps. The older battery technology would never provide this much power, limiting the heat produced. But, a Li-ion will. This will cause the flash to generate heat with each discharge/charge cycle. If this happens in rapid succession, the flash will be fried. So, when choosing your power supply, use a switching power supply with a current limiting adjustment. The four AA batteries in the flash will put out less than one amp of current. That's a good place to start with your current regulation.


I have a six AA battery NP-F holder here. I'll load it up with fresh AA batteries, test it and post the results here. Years ago when I purchased this I thought this would be a good idea. But then it occurred to me this is the same physical size as a Li-ion NP-F pack. The mAh with AA cells will be a fraction of the mAh with 18650. So, I never used it.




UPDATE:

I loaded the pack with six white Sanyo eneloop AA batteries. All six batteries were about four years old and have been used in Nikon flashes. I wanted to test with six black Panasonic eneloop Pro batteries but I only had four in stock. The white Sanyo eneloop batteries are rated at 1900mAh. So, in a 6S configuration the NP-F pack should have a capacity of 1900mAh. The test ran with a load of 500mA and with a cutoff voltage of 4 volts. The first test resulted in a capacity of 1886mAh. Not bad for older batteries.

The Panasonic eneloop pro is rated at 2450mAh. I ordered a four pack and will test them when they come in.

But.....two genuine Panasonic 18650 batteries in series will produce the the same voltage at 3400mAh than six eneloop AA batteries, taking up a lot less