I've had a couple of Di2 batteries fail. One of them went suddenly and I had to grab a train to get home. The other one lost capacity quite quickly, so I'd have

I've had a couple of Di2 batteries fail. One of them went suddenly and I had to grab a train to get home. The other one lost capacity quite quickly, so I'd have to charge it once a week until it got so bad I needed to charge it fully each day until I swapped in a new one.