"battery mounting should be easy" - famous last words, said before i test fitted a hailong 'shark pack' in various locations.
There is no happy ending here. The case adds a lot of width. I'd guess there's an extra 10-20mm of width added on to the 18650 cell's width.
I noticed that if the casing was minimal ( an 18650 vape is used to illustrate ), and the chainring was located on the outside ring position rather than the center, and the inner chain guard was removed, then i could pull off the front battery mount.
However, the taylor spatial frame on my right leg would smack the chain/chainring when mounted up front, so for the time being, this can't work.
I'm considering my options.
1) I pull the case off, hit it with an angle grinder, bolt thinner side plates on, and then i have a pack that's narrow enough to clear the crankset and chain. Unless it's got a super wide BMS or something else inside that gets in the way.
2) I install a schlumpf / ATS speed drive / patterson metro /etc and reduce the chainring size significantly, giving me an extra inch or two to mount the hailong closer to the handlebar tube. This would remove ~2lbs from the back of the bike and add it to the front of the frame, which is great and all, but comes at a price. This also dorks up the goal of high efficiency because planetary gear reduction drives have a friction penalty. Also, with no front suspension and a tiny wheel, the battery gets to
3) I do a super complicated and heavy upside down mount.
4) Totally custom battery pack that's mounted on the sides or along the top tube, but remains very narrow.
5) internal pack like cowardlyducks' won't work because there isn't even space to mount 2 18650's side by side.
I am concerned about mounting the battery on the front because the front wheel is not suspended and transmits a lot of vibration to the front of the frame. The handlebars provide some isolation for the rider, but surely the front of the frame is getting rocked about.
If i didn't have rear suspension, the pack could be located where the swingarm is, missing the chain. However there is no way in hell i'd ride a bike like this without suspension.
I'm going to take a break on this bike and give the cannondale some love. When i get the device off my leg, i will re-evaluate. This will remain a pedal bike and will be used as a platform for testing aerodynamics mods. The current gearing on the bike goes up to 30mph, so i figure it's ideal for experimenting.
Here's the "solution" that maxarya came up with on their Ray 2 E.