Lead acid batteries can get a polarity reversal within a cell if the voltage gets below 1.36 volts per cell. Each cell should read about 2.27 volts dc when charged correctly (2.27 volts per cell x 6 cells = 13.62 vdc measured across the complete battery). In order to overcome the polarity reversal within a cell you must be able to charge the battery with enough strength to overcome the internal resistance of the reversed cell. A battery tender only puts out about .5 to .75 amps at 12 volts. This is not strong enough to do the job.

Get a 10 amp charger and you may be able to correct the reversals and recharge the battery. Don't go any higher than 10 amps or you could cook the battery and ruin it from internally generated heat.

Good luck and make sure the battery is out of the bike before recharging. The battery will give off Hydrogen gas from the sulfuric acid in the cell and it is corrosive and explosive. (Hard on paint in either case)

 

Ordered a charger... just waiting on delivery thanks for asking

 

If I remember correctly, a Deltran Battery Tender will not charge a battery if it is below a certain voltage. If your battery is really low like zero volts, the Battery Tender will not work. Best bet would be to put it on a charger, not a maintainer, that puts out 2-5 amps of charge to try to bring it back.

Chances are the battery is damaged as some others have said and may not work properly even if you get it to take a charge. If you do get it to charge, I would do some tests on it before I put it back in the bike, like a load test or even just letting it set on your workbench for a few days to see if it holds a charge.

 

I had a Harley tech tell me you can jump it from a car, but don't turn the car on. I certainly wouldn't use the car to charge the battery though. I left on a 7 month deployment and forgot to put mine on a charger. That battery was dead as all heck and I had to replace it. I've had it go dead a time or two before then due being away from home for training, but jumping it worked then. One cue is whether your lights come on strongly or if they're dim when you switch the power on before start.

 

I left my lights on my 08 about 6 months ago and the same thing happened. I tried the tender for about four days then off to the dealer for them to check it out. They said I could either buy a new battery or try to charge and see if it would work. I figured why not try and see worst case is i am out riding during the charge. I came back the next day and the battery was charged up and ready to go. Out no money just a few days of riding. As other said the tender is for maintenance, not charging, put it on a charger and hopefully that works out.

 

UPDATE... Got myself a manly charger from sam's club ($25 shipped free, half the price of the battery tender). sat on the charger overnight. Dropped it in the bike this morning......Started right up.

 

Thanks for the update. Good to know these HD batteries can still be revived even after being drained all night like yours was.

 

Great new on the battery and the charger......thanks for letting us know.

 

This thread was a big help. I left my switch ON for 2 hrs (cause my brain was OFF) and the battery was dead. I couldn't even get it started jumping it with my car. I removed the battery and had it on the battery tender and thought I should do a bit of reading on HD Forums. After reading this, I ran out to Sears and they had a charger on sale for $44. I have it charging and am hoping for a happy ending to my story, too.

If anyone needs a charger you should check out Sears, it seems like a good deal.