Good to keep an old flashlight going but seems to be old technology...

Fenix ARB-L4-4800 Using this battery in an FD40.
Working on a vehicle where I had the FD40 on its highest setting, it lasted about 30 seconds before the battery shut down. Thought it was the FD40 so I replaced the battery with same, with the same result. The second battery quit the same way. Now I never use the highest light setting, so everything works fine.
I'm thinking that my flashlight can exceed the current limits of the battery.
Love the FD-40 mainly because of the focus feature. Love the battery because of the 4800 may capacity.
Wish I could change the max current draw for my light.
-Jim-

It's a good high capacity battery

Worked as expected, also great customer service. If i have more need for unique batteries i will definitely reach out again.

Really great battery I can sure see the difference it makes!

Great product!! Fast shipping!! Great price!! Highly recommended!! I've told all my emergency services friends and coworkers!!