Hello guys,

unluckily my Transalp broke down. My first thought is that the battery died. I will check that this evening, I'm at work now. Ah btw, it's an Honda Transalp 600 from 1998.

I am a full beginner to mechanics and electronics so I might have questions that are super clear to you, sorry in advance. I already posted the story in the Facebook Transalp group so it might sound familiar if you guys are in there aswell. I post the full story as detailed as possible and what I will try this evening. Any thoughts and tips are very welcome.
Sorry for english errors, I try to be as detailed as possible.

So 3 weeks ago I installed a cable to the battery. It is for my navigation System, sadly it didn't fit directly ON the battery because those metal connection rings at the end of the cable didn't fit.
So as a conclusion me and my dad decided to plug it directly on a cable that was already plugged on the battery via such a thing. We both had no idea what it was for, it is definitely after market tho. It looks like a power supply but it's neither USB or the usual car plug for a cigarette lighter. It looks more like a cable i know from my computer. It is similar to this... I will add photos later today.
I never left the Navigation System on the bike tho, when I left it.

So far so good, the Transalp still started instantly and I rode around 1000km in the upcoming week. Then i didn't ride for 1 week, until yesterday. I tried to start the bike and it needed a second try (usually it's starting instantly), okay it's an old lady so no worries. I then drove about 10km and decided to get gas. I paid and wanted to drive on...the bike was not starting any more. I tried several times...panicking and full of shame. It didn't start. So I decided to ran it in the first and then in the second gear....I couldn't get it running. All I got was a buzzing Sound from the battery. Not a single sound from the engine. So the battery was out of power...BUT HOW? I just drove 10km...

I then pushed it to a closeby Mercedes seller. Luckily there was still one mechanic, he bridged the battery and the Transalp instantly started. So I got going and after 2km I had to stop at a red traffic light (it was the third already)...after about 1 min the engine just went off. Like Puff, Over and Out. While i was waiting I checked paranoid the RPM and when it turned off it was on about 1400RPM with the Choke pulled in.

I don't have to say that it didnt start again... So I called a friend who got a trailer for motorcycles. We brought it home and now I have to find the error.

What I will do tonight is to unplug that damn navigation cable and get rid of that electrical plug aswell. Then I will put out the battery and reload it. After that I will check if the voltage is at 12,5 Volt, like someone told me to. If that's the case the battery might be okay, if not, the battery is dead.

After that, even if the battery is dead, I will put it back in the motorcycle and start it (should workout if I just loaded it) and check the voltage at around 5000rpm. If the voltage is below 14,5 Volt then the light machina (right translation?) might be the Problem. If it is way over 14,5 Volt then the charge controller might be broken and destroy the battery.

What's left then is WHAT is causing the battery to die and why the **** did the engine just stop running at that traffic light -_-