There is no charge port on the bike, the battery can only be charged off the bike. The bike/battery connector is a complex custom 4-lead job which would be hard to interface with anyway.

No other connectors on the battery, no way to access the cells without opening it and voiding warranty. I'd not want to do that sort of surgery anyway.

Yes, a dynamo would work. I've actually seen ebikes specced with that. It's nice to have lights even if your battery is flat. It's a 15mm thru-axle front wheel, but afaik hub dynamos for that axle do exist, so it's an option. In that case the E-werk could be good.

Or I could of course just add a second battery to the bike, but I'd rather avoid that extra charging hassle. If I can't find a clean way to do the job, I'll just drop it. The bike is too good (and expensive) to risk hacking apart.

Thanks