Originally Posted by
oldnslow2
Single point of failure, if it goes, you're almost walking home.
Shifter batteries are good for a year, actually I spoke to the Sram rep and he said the real life is much longer than advertised. So just add it to your winter maint along with new chain, new brake pads and new cleats.
Derailleur batteries are interchangeable so if for some reason you forget for a month to recharge them you can always move the front to the rear since the front is used so much less.
Are Di2 batteries failing often?
And seriously, if you did have to ride without GPS or power data that is almost walking?
If you forget to charge it, Di2 already accomplishes by software, what the 2 separate batteries do with SRAM. As the battery runs down, you lose front shifting first, but you still can shift the rear.
So functionally, you'd be in the same place you would be with SRAM.