You have discovered the problem with high output lights. The brighter the light, the shorter the runtime. I took the plunge a couple of years ago and bought a bike light with five CREE XML-T6 LEDs. It was incredibly bright but the run time was dismal. It came with an 6,400 mAh battery pack that would run it on high for under 2 hours. So, I bought a 12,800 mAh battery pack. The smaller one weighs just under 8 oz and the larger one 12 oz. Ditto for 4 NCR/Panasonic 18650 batteries - 7.5 oz. I discovered the five Cree light was a waste of money. I didn't need that much light in an suburban area with good street lighting and I hated using battery packs. The smaller one would fit in a water bottle cage but the larger one would not. You still have to deal with a dangling wire every time you mount the light. Eventually I just used a good LED flashlight. I can switch out the battery in a few seconds if needed and it is far easier to deal with than a separate bike light. I use a simple 360 degree flashlight holder so the light clips in and out but never comes loose. I can aim it precisely where I want the light to go.

Not terribly impressed by the information available from either the Outbound company or the source of the LED in the light. They measure the light output in LUX which is not directly translatable into lumens which most bike light manufacturers use to show the output. One review in Road Bike Rider (https://www.outboundlighting.com/store/) gives the high level output as :"1800 equivalent lumens" so this light has roughly the same output as two CREE XML-T6 LEDs. A spare battery pack is $85 and the light with one battery pack is $193. There is no doubt the battery pack is made up of four 18650 batteries. Good quality NCR/Panasonic 3,400 mAh batteries sell for way less than $85 for four of them. A waterproof battery pack to hold them is around $10-12. I can still find the batteries for $5 to $7 each on eBay.