Saturday night I accidentally left the switch ON, and the lights drained the battery overnight. The next morning the battery was dead, and the voltage across the terminals was 6.3. I didn't think it was possible for the accessories to deplete a battery charge that deeply.

I don't have a charger or jumper cables, but I put a Battery Tender Jr. on it (0.75A charge rate). After almost 60 hours, the charge is up to only 6.5! The BTJr instructions say it should be able to charge a 12 volt battery in 16 hours.

My main question is, did it discharge too deeply to be brought back? The battery is only 8 months old and the bike has 1700 miles on it. I should:

1) get a real charger and hook it up
2) start the bike with jumper cables and ride it for a while
or
3) buy a new battery

Which do ya think?

 

I may not have the correct answer to your question, but I would try to jump start it before I bought a new battery. Batteries also carry a warranty. Might be able to utilize that.

 

I would first put it on a charger that can be set to charge at 10 amps and see if it comes up after 30 minutes or so. If it does not come up get the battery replaced under warranty. If you want to jump start the bike using a car, make sure the car is NOT RUNNING when you jump the bike...

 

That doesn't sound very promising! A deep discharge with a modern battery can be terminal. If you can charge it fully with a proper battery charger (as you have discovered, a tender isn't man enough!) you can then get it load tested at a local auto store. That will diagnose if it has any useful life left in it.

I recently installed a new battery on my Buell and only a couple of weeks later left my lights on for a couple of hours (can't be certain exactly how long). Started it off another bike and it has been fine since. We didn't have a voltmeter to check, but it wouldn't turn the engine over on it's own. So check where your key is before retiring at night!

 

Make sure you didn't blow the tender fuse

 

After a starting battery goes that far down, it takes a real hit even if you do manage to bring it back. From your description of trying to charge it back up, it doesn't sound too good that it's a viable battery with a long life ahead of it.

 

A battery tender is just that - to maintain a charge in a good battery. To charge the battery back up, use a regular charger. I've seen batteries down to 4V recover nicely. Don't jump it off a car or other vehicle.

 

Interesting the different opinions. I'd be inclined to bring it up as steadily, slowly as it had been discharged. That usually means a low amperage, trickle charger running for 24+ hrs. A battery tender can do that. Should be 1 or 2 amp max charger.

 

Guys the posting is over eight months old ... pretty sure it's fixed by now :>)

 

well . some said a really slow charge