I guess I will just have to keep a fresh battery in it at all times and stick partially used ones in something else.
sounds like you are using depleted CR123...
the light cant get maximum output out of a depleted battery.
so even though you have the dial set to maximum, youre only getting about 20% of the potential output.. and the light is telling you it needs a fresh battery..
is there some reason you choose not to use rechargeable batteries?
per the manual:
"Lithium-ion rechargeable batteries are fully supported and recommended for lower operating cost. "
"No special actions are needed to use rechargeable Lithium-ion
batteries. Your flashlight detects them automatically."
"In general, primary (non-rechargeable) batteries provide longer
runtimes." [but only at a small fraction of maximum output]
"However, rechargeable batteries provide a lower cost of
operation and allow you to always leave home with a full battery." [so you can have maximum output]
fwiw, HDS considers 50 Lumens the minimum output to qualify as a "Tactical" output
. So essentially it is blinking to tell you that your battery will soon no longer be able to produce a "Tactical" brightness.
A fully charged battery can give you 200-250 Lumens
.. (depending on what LED your light has).