So, finally got my Energypak extender a few weeks ago, and then had to wait for the shop to update the firmware so I could actually use it (Giants app decided it hated my bike on every device I tried to connect with). First ride was today, and I figured I'd pass along a few thoughts in case anyone is looking at the Revolt (or other 2020 Giant) and was wondering how the extender works.
First, mounting and connecting it is pretty simple. Charges off the same charger, but has a different plug So now I have the charger, which has a plug that plugs into the charging port on the bike to charge the main battery. Or I can remove the battery and use an adapter to charge that. Or I can use a different adapter to charge the extender. I feel like they could have standardized those a bit, but what do I know.
As for how it works, it seems to talk to the computer, which displays a percentage based on the combined capacity of both batteries. It also seems to draw from both of them while riding, though not totally evenly (after my ride today, I was at 31% left. After unplugging the extender, that dropped to like 14%, so the controller favored drawing from the main battery). Not sure how it decides how much to pull from each one. The extender has a USB port on it if you want to use it as a giant mobile battery bank for whatever reason.
Also, you can't use the bike with just the extender on the bike. It throws an error. It seems to need a main battery plugged in before it will go.