Forerunner 255S charges only to 83%

Have you done a long power down. Hold the power (light) button in until the watch powers off. Then restart it. That sometimes helps with some matters.

I have had a similar problem.  Someone suggested elsewhere to press the power button once and the watch goes into some kind of quick charge mode.  This has worked for me and watch is now at 100%!

After second charging everything was fine. Maybe battery or watch needed to learn capacity. Many thanks for all answers.

I have a similar problem - my watch initially charged to 100% for ages, then started only getting to 90-something %, then it went down to 88% and now it's only charging to 86%. Watch isn't even 6 months old. I have updated the software and done a factory reset... any other suggestions?

I have the exact same problem on my wife’s Forerunner 255s. It now only charges to 76%. I’ve updated the software and reset the watch. This forum alos has reported the issues. Reddit Forum 255s Won’t Charge to 100%

I’ll be contacting Garmin today. 

Thanks for that. I've done a restart and plugged it into our Mac.  The software is up to date. Garmin Support told me to let it drain to 0 then recharge it. I"ll post my results here. It's obviously a bug since people here and on Reddit are seeing it but it must be pretty isolated with so few reports.

You're welcome. I take , it did work for you as well

No, I have not done a full reset yet and am still waiting on the watch to drain to 0% per Garmin Supoport's suggestion. I'll post my results here.

My wife's 255s Music has a similar problem. It only charges about 90%. When I unplug the charging cable, the % number may change. A full reset or discharge(0%) didn't help.

I contacted Garmin Japan and got a replacement, but the symptoms are the same even with a new watch. Garmin Japan doesn't seem to know the bug.

I'm sorry that I can't speak English. I am writing from Japan using Google Translate.