R1150gs 2000 battery light stays on even with ignition switched off

[gags]

Just started my new to me 1150gs after working on it quite a bit to resurrect it after previous owner had not started it for 7years. It started right off and seemed to run perfectly with new spark plugs, fuelpump, filters, all fluids etc etc.
After letting it idle for a couple of minutes I turn it off and the battery light stays on. It turns off after starting engine exactly as it should. I have it on a battery tender (new odyssey battery) and the battery light just stays on. The tender does not seem to charge the battery above 75%. Battery light stays on without ignition key and tender.

 

[jrogers]

He said the battery is new.

 

[gsaddict]

Put a voltmeter across the battery when the engine is running at 2500 rpm.
(this can also be measured at the plug on the starter cover)

What voltage do you read?

Next: Disconnect the D+ (small blue wire) on the alternator.

Does the light go out?

 

[gags]

Update

Thanks for the advice! Did run into this thread https://www.bmwsporttouring.com/topic/94618-battery-lamp-stays-on-even-when-ignition-is-turned-off/ that appears to describe my problem. Another symptom pointing to the ignition switch also came up; twisting the cable leading to the ignition switch even a little cuts power off the entire bike (leaving the battery light still lit). I ordered a new ignition/light switch from EME. I’ll change that during the weekend hoping this will resolve my problem. In the meantime I disconnected the battery and the tender has restored it to 100%.

 

[gsaddict]

Exactly what I asked you to do.

 

[gags]

Thanks for the advice. Took me a bit long to get back with an update as I did not have time to work on the bike.
Did what GSAddict proposed and turned out the alternator was shot. Besides the alt light staying on even with ignition off it also appeared to be shorting as it got warm to the touch and draining the battery quite quickly. Remedy here was to order a new Enduralast alternator from EME. For me this was a pretty laborous task as you have to remove the abs unit and motronic unit to get to the alternator. After a couple of weekends I managed to make the replacement (as well as new belt). Also replaced the ignition switch due to what I described earlier.
All turned out well, except that a new problem with abs warning lights alternate blinking. Did the reset, did not help. Will try to troubleshoot this over the next week or so…