Originally Posted by
angerdan
You can use an 2S2P case for 18650 cells:
Fenix BA4C Case found- Mtbr.com
Review: 4 (2S2P) and 6 cell (2S3P) hardshell waterproof bicycle battery packs from GB- Mtbr.com
Or go for an "Assembled in Germany" battery pack:
ENERpower Mitte Plus Battery 7.4V 10200mAh with Round Plug at ENERprof
Bike Light Batteries at ENERprof
It will get much more heavier, so mounting safety isn't that good anymore. Also many would complain about he size and weight...
You can get an Fenix BC30 if you like an bright light (but it has no cutoff-beam).
Specialized Flux Expert has an cutoff-beam, but battery is only replacable with tools.
Comparative Light like the Lupine SL A or B&M Ixon Space costs $200-350. So the price is okay.
If a light reaches 1.500lm, this is automotive level brightness. So finally bicycles are up to other vehicles, after more than 120years. So brighness would last some years.
With electronics and good CRI lamps can reach >120lm/W, but would be more expensive then. Reaching 100lm/W is already very good.
If you'd buy the Supernova M99 Pro back in 2015, it will be even compare with the best bicycle lights in 2020.
Same with LED retrofit bulbs from Philips, 60W/806lm did cost $60 back in 2012. Now they still work fine, only the current price for similar lamps would be just 1/6 of 2012.
If I buy a $175 light I expect to not have to McGyver a battery solution....
For $60 I got this
1000 lumen helmet light. works really great and is a good addition to any handlebar light since it shines where you look at. In addition I have a $30 flashlight (which is an expensive one compared to most) that has over 1,500 lumens and also an 18650 battery. Back when I fell for that specialized bike light idea I also bought a $60 600-lumen niterider light (not replaceable battery) and use that as second headlight. Once that Niterider battery dies, I replace it with a flashlight.
From a light distribution point that outbound light may be better, but price and battery situation greatly favor my "cheap" solution.