not another steady versus blinking, battle, please..

FWIW Here's a LED taillight, set inside the seatpost [If no saddlebag is to be left on a parked commuter bike)
?25.4mm LightSkin seat post with LED rear light - silver · EpicBike · Online Store Powered by Storenvy

I have a B&M 4D toplight senso plus, and 2 toplight line plus taillights (plus is dyno hub powered )

the older 4D design uses a pair of AA batteries to power its 4 diodes
senso Feature allows you to just leave it in that mode,
it will turn itself on when you start rolling , and off after a couple minutes ..

great for those who forget And leave their battery light on & and find the battery drained when they come back..

the non Plus has an off position , the Plus the off position is the dynamo power, it goes off when you stop.

the newer ones the capacitor charging is the battery for the standlight. it comes on quite quickly when the dynamo turns..