As the title says, I have an 88 BMW K75 that was left parked, covered for 10 days while I was on vacation. I'd ridden it multiple times in the days leading up to going away. When I got back, the battery was flat dead to the point that the time wasn't even displaying on my Acewell speedo and my smart charger wouldn't even pick up that a battery was there.

I'm fine going out and buying a new battery, but I also wanted to find out if what happened is normal. I know batteries discharge over time of not being used, but to have a battery go flat dead in 10 days - does that just speak to the battery itself finally giving up or something possibly more nefarious in my electrical?

For reference, I've done a fair amount of electrical work on the bike to install a BEP, new speedo, LEDs, and relocate the ignition by removing the power socket attached to the coil cover and running the ignition into that spot.

I've never had an issue with power draw like this before or errant power issues like fuses going, etc. so I'm hoping it's just an old battery giving up the ghost.

Thoughts?

If it's a normal lead-acid battery then they can die pretty much overnight when a cell finally goes 'bad' because of lead sulphate build up. Assuming this is the case, if the bike is a good starter then riding the bike regularly would have kept the battery topped up enough to start the following day, but if the bike decided to have a bad hair day then the battery would have died pretty quickly during the start cycle.

Leave the smart charger on for a few days. It might find the battery eventually but unless it's one of those that runs a charge/discharge cycle to break down lead sulphate, I wouldn't really trust the battery again.

Only abandon a moto with a well-charged battery if you've disconnected the battery's ground cable from its transmission mounting point. It should start the moto when you return in six months and reconnect it. That's been my experience.

Thanks for the replies... This all happened yesterday and I found a trick online to get the smart charger working by touching a 9volt battery to the clamps which kicked it on. It charged for for a number of hours and the clock came back on and said the battery was fully charged but also a red light on the charger which apparently means 1 of 10 different things.

I tried starting it, it gave a quick attempt and then nothing, tried again, quick click and nothing. When I hooked the charger back up to it this morning (I can't leave my motorcycle in my apartment's garage overnight) it recognized the battery immediately and has been charging for the last 5-6 hours.

Not sure if I should trust it even when/if it shows fully charged

I doubt that the 10 day sleepybye did anything to your battery. It was most probably kaput before you drove out the driveway. But you need to check for a parasitic short before you go too far with a new battery just to be sure.

Also check the charge voltage from your alternator. Should be 14v ±4v @2k rpm. If it's not, remove voltage regulator and give it a clean and check the brushes.

Let it charge all day yesterday and into today, the battery charger gave it the literal green light. I took her out for a ride and everything went smooth. I parked it in front of my apartment, not on the battery charger and plan to check the voltage tomorrow morning to see if it's dipped and if there's a parasitic short somewhere.

Cheers

Battery a bit flat after a 10 day holiday yep that would leave me a bit flat too. I recall having to go back to work to recover after a 2 week holiday once.