No, I'm not relying on the battery widget on my phone; it (naturally) only shows the status of the active watch battery. (Too bad it won't show all paired watches but whatever.) I just got the 9 yesterday and this is my first attempt at having multiples paired to my phone. My 6 was at 83% battery when I put it on the charger to "top it off." I checked it about 30 minutes later and it was still at 83%. I tried this a few times and on different chargers.
I have tried pairing/unpairing, restarting all (phone, both watches), etc.
@Jackbequickly -- My 6 has not had any issues prior to this so I don't believe it is the problem. I'm sure it's something I'm missing somehow.
I'll just keep working with it now that I know it should be working. I'm finding that several little "glitches" seem to be working themselves out after putzing with settings. Thanks to all of you for your responses; I'm happy to know that I should be able to wear one/charge one!