I didn't see any posts about this bag, so I thought I'd post my quick thoughts so far. I just got this bag for my build. I was looking for a smaller triangle bag to fit my full suspension bike. The standard em3ev and luna bags won't fit.
This bag fits the 60V - 21Ah Triangle Battery from West Coast Electric Cycles very well. It should also fit the EM3ev 52V (14S6P) Hard-Case Triangle Battery Pack as well, since those batteries are nearly identical in size.
There's a small amount of extra room for some high density foam for cushioning. I may need to reinforce the straps with extra zip ties since the straps don't seem very strong.
But, doesn't look too bad for $27. I got the larger 8L size:
Build so far:
2010 felt virtue 1 - Bought used from Craigslist with some mods
60V - 21Ah (14s7p) 30q Triangle Battery from West Coast Electric Cycles
Crystalyte Crown TC3080 Rear Direct Drive Hub Motor laced in 24" Mavic 319 MTB disc rim
7kW eBike Sinewave/Silent Controller from Powervelocity.com
Domino Twist Grip Throttle - 0-5K Ohm from evdrives
2x Grin TorqArm_V4
Cycle Satiator 72V 5A
35 mph top speed, maybe more with field weakening
30 mile range @ 30 mph
Not concerned with off-road capability
I'm about $3k invested so far, and wish I could have just bought a Sur Ron instead! Hopefully someday we'll get a Sur Ron with a VIN so I can register it as a moped and ride it on the road...