Originally Posted by
Bonzo Banana
The compactness is not the same because of the battery bag I didn't mean anything beyond that. It's an extra item. Some solutions use an internal increased frame tube solution which slides out and has no real difference between their standard and e-bike folding size just a weight penalty because of the battery and motor hub.
For a folding bike I think the external battery is the better solution. The "weight penalty" for the electric conversion on the Electric Brompton is about 5.5kg in total, about 3kg of that is in the battery-package. The total weight of the Electric Brompton is 16.6kg for the 2-speed and 17.3 for the 6-speed. Too much to carry comfortably. With the Battery being an extra item at 3 kg to carry over your shoulder what's left for the bike is 13.6 respectively 14.4 kg. Still a lot and a bit on the heavy side but possible.
When my steel Brommi was fully equipped with lights, rack, Brooks-saddle and the S/A-8-speed-hub it weighted around 14.5 kg. This was the absolute upper limit I was willing to carry. In fact I "downsized" to the 6-speed BWR to save 1kg of weight - which made a hell of a difference. Still I like my Titanium 2-speed more when it comes to carrying - it weights just above 10kgs. Easy to handle. The sweet-spot is from my experience around 12 kg - more than that makes it more and more uncomfortable.
Therefor I think it would have been a bad idea to integrate the additional 3kg fixed into the bike. Regarding the compactness: I ride 99% of the time with a bag on the carrier-block. Therefor at least for me nothing would change regarding compactness. Plus an external battery is easier to charge or to swap.