Letting the battery go completely flat now and then shouldn't really hurt. But letting it completely discharge often can shorten it's life. It might recover if you leave it for a while.

I guess you don't have a charger. What I'd do is run out and buy a small charger/maintainer. You can get them pretty cheap at places like Harbor Freight 6v/12v 2 Amp 3-Stage Microprocessor Controlled Automatic Battery Charger

These small chargers/maintainers will charge up the battery.. It just might take a few hours. Plus if you ever put the bike away for an extended period, the charger will keep the battery full over long periods.. (Months etc)..

 

Thanks for the suggestion. Will be heading by a harbor freight here in a bit.

 

don’t get a cheap one though. for a few bucks more you can get a ‘smart charger’ that will slow the voltage as it gets more charged and then maintain it automatically. it will also charge at multiple volt output.

 

I agree with Badboir.. and just to add.. Getting a larger capacity charger will charge up your battery faster, and you will even be able to use it for your car should that battery go dead.

Make sure it's an 'automatic' or 'regulated' charger with the ability to trickle charge.. If not you can overcharge a battery which isn't a good thing.

 

If the battery went so dead that the chemical process inside the battery stopped. It might not accept a recharge. As jwt873 suggests get a charger/tender. A battery cannot be kept on a trickle charger all the time. The charger has to be a tender, not a constant charger.
You can also remove the battery. Then take it down to the auto parts store and let them charge and load test it. They do it for free.
Here is a link to download the factory service manual.

KAWASAKI VN900 CLASSIC SERVICE MANUAL Pdf Download

View and Download Kawasaki VN900 CLASSIC service manual online. VN900 CLASSIC motorcycle pdf manual download. Also for: Vulcan900 classic lt.

www.manualslib.com

 

Whatever you do..do it soon as the battery sitting dead will shorten it life.
Also...if the battery is completely flat ..many chargers won't pick up that it has battery attached to it...and so will do nothing.
You could jump it with a vehicle...let then booster vehicle idle for a couple minutes..unhook the booster cable..and it should have enough for the 'smart chargers ' to pick it up.
I wouldn't boost it very long with an automobile as our batteries are pretty small .

 

If you can find one quickly at a reasonable price, get one that specifies that it has a desulfonation cycle. This will reduce some of the damage from letting the battery drain completely, but some damage will have been done, and as Tourer noted, the longer it sits dead, the more damage will be done. However, any smart charger is better than nothing.

 

You could jump start it and go for a long ride

 

Didn’t make it by harbor freight today. Got back home, jump started it. Let it idle just a bit. Went on a short ride. Turned it off. Turning it back on it had enough juice for the lights. Not enough to start it. Probably should of gone for a longer ride.

 

Success. Got me a good charger. Out for a good long ride. Cranked right up on this cool morning. Lessoned learned. Don't leave the darn key on the bike !!

 

So how old is the battery?
All it takes is one time fully discharged to weaken and shorten the batteries life.
As you saw the first short ride you took didnt do anything to charge it.
Now is seems ok, until that other day when it wont start.
If its 3 years old, save yourself trouble and get a new one!
AND remember turn the bike off WITH the key!

 

It’s a 2021 VN900. Bought a few months back. I’ll be keeping an eye on it. Hoping that since it ain’t that old it will recover ok. If it don’t , I’ve got some free battery replacements from the dealer coming to me. Would of done that already. Just got a lot going on right now. As the weather gets colder, I may just replace it then. 😎

 

My worry is leaving the key in the ignition or losing it in my pocket. As i dont have a ring on it or any other keys for fear of it bouncing around while riding, its pretty minimal in size..
I guess you could get used to turning the ignition with the key and then removing the key for the duration of the ride.

 

My worry is leaving the key in the ignition or losing it in my pocket. As i dont have a ring on it or any other keys for fear of it bouncing around while riding, its pretty minimal in size..

My key is by itself as well.
I dont want to scratch up stuff with the bouncing around.

I dropped my single key one time and it took a loooong time to find it. I didn't want anything on the key that would damage the finish, but I needed it to be more visible. Had some blaze orange nylon string, like builders use. Went online and learned how to braid, and now have a 3" orange "tail" on the key. Doesn't harm the bike's finish, is highly visible, and is easy to find in my pocket. I also taped a spare key to the frame in an inconspicuous place, just in case.

 

My key is by itself as well.
I dont want to scratch up stuff with the bouncing around.
But if your key comes out when the engine is running you have ignition switch problems.

 

My Vaquero has an "Accessories" position on the ignition and I've left the stereo on for days at a time. Yes the battery was so flat no dash lights would come on. 4 yrs in and it still starts the bike every time (as long as I don't leave the damn accessories on, that is). Next spring there'll be a new battery in her, but '17 to '21 ain't too bad.

 

I recommend the Battery Tender brand chargers. Put the pigtails on the battery and plug it in every month at least. Unlike some, I dont keep my Bike plugged in 24/7 whole sitting. That’s another discussion for debate that I won’t start. Theoretically the battery tender quits charging at 100% capacity. Also, a fabric key fob works great to give some substance to your key while not scratching any surfaces, and you can even get one that has “KAWASAKI” printed on it. 😀

 

on my custom, having a key with a ring and small keychain has not been an issue in the 5 years I've had it.
I also use a battery tender brand for juicing up the battery if its been left too low - and for maintenance trickle charging in the non -riding season.
I'll typically plug it in during the winter if I go to the garage, and then unplug it again several days later. repeat every other week or so

 

i've left the key in my bike a couple times. both of those times, were the only times i ever wished i had a carb. both times a buddy's car and some jumper cables got me running, and i just rode the bike around long enough to charge the battery over the next few rides. i don't have any battery problems 4 years into this bike so far. my bike sits under my living room window under a cover. i had a shed, but it blew away in a storm a couple years ago. anyhow, i don't put a battery tender on the bike. i just go out there every 3 weeks and run the bike for 20 min or so. that also keeps the fuel from getting too stale.