Bummer no one seems to be able to answer this question. But that's okay, after further considerations I think it's just better getting a spare battery.
I have an Intense Tazer, so swapping out a battery that stores easily into a camel back is super quick and easy. Plus 90% of my rides the 504wh battery is more than enough. It's only on rides that I go past 3,500 ft of elevation that I need more range. I don't do big rides like that often.