I've carried a spare battery but never needed it, I find my arse giving up before the battery.
This is what I use in my kreiga backpack, you could mabe strap a kreiga us10 or so to the bike but there's downfalls either way as you already know.
I've got these if yo want me to fuk about with the battery strapping to the bike
If this fella can carry a chainsaw on a dirt bike then I'm sure you'll be able to find a way to carry a spare battery .
deuter E-Pocket | Bike bags
deuter Bike bags E-Pocket: E-biking: Padded bag for e-bike batteries Max. battery size: H 420 x W 85 x D 65 mm (sized to fit largest Bosch frame battery) Designed to
www.deuter.com
I've got these if yo want me to fuk about with the battery strapping to the bike
Enduro Engineering Dirt Bike Chainsaw Mount - great for trail maintenance
The Enduro Engineering Dirt Bike Chainsaw Mount mount makes it easy to lug around your chainsaw and also is easy to access on the trail.
slavensracing.com