I have two S1 Pros. When I got my first one, I charged it fully and used it for several shows (I'm a magician and I use it for a vocal mic and background music from an iPod). When I finished my third show, it was down to flashing twice which is supposed to mean 25% to 49% battery life. I didn't use it for five days and then turned it on for a show. It was completely dead. I plugged it in and used it with AC. I called Bose to see what tech support would say about it because that's not the behavior I'm used to seeing out of lithium ion batteries. I have lots of photographic equipment that uses lithium ion batteries of all sizes.
The tech support representative recommended running it through a couple of charge cycles to see if it improves. On the second charge cycle, it exhibited the same behavior. I called Bose again and they sent me a replacement battery.
In the meantime, I bought my second S1 Pro. I charged it fully and used it for three shows (two were paired with the first S1 Pro using a 1/4" TRS cable). After the third show, the second S1 Pro showed 25% to 49%. I did not use it for 5 days and checked it today. It turned on, flashed one time and then immediately went to red so it exhibited the same behavior the first one did.
Has anyone else experienced this? I'm trying to decide if this is normal for the S1 Pro or if I somehow got two bad batteries.