Yesterday I was doing pre-ride check on the bike before an intended long ride when a line of severe thunderstorms came through. So I went back in the house to wait it out. Unfortunately, I left the ignition key on (I'd been checking the lights). I have auxiliary headlights and all three were burning. When I came out after the storm several hours later, the battery was completely dead.

So instead of a nice ride, I drove the cage to the dealership and bought an H-D Global Battery Charger (1.25 amp). The previous owner of my bike had already installed the terminal plug, so I had a direct connection rather than alligator clips. I plugged it in around 5 PM yesterday and at midnight the light was still yellow (charging). At 8:00 AM this morning it was flashing green, meaning 80%+ charged. It didn't turn solid green until about 10 AM, meaning fully charged.

Does the fact that the charging took so long indicate there is a problem with the battery, or is that normal? The instructions said it could take 10 hours for a full charge of a dead battery. It obviously took much longer than that. I'm about to head out for the long ride I wanted to do yesterday and wonder if I can be confident in the battery.

(I also bought a battery tender which I am told I can use every night even if there doesn't seem to be a problem. Is that a good idea?)

 

You have a 1.25 amp charger and a 20 amp hour battery. That's 20 amp hour / 1.25 amps = 16 Hours charge time.

It's always much better for the battery if you slow charge it, but I also keep an automatic 10 amp hour charger handy when I don't have all day to wait.

 

1.25 amp charger..take a long time.

I'm not a fan of bringing back dead batteries, especially if they are old.

 

It's fine to leave a tender on all the time. I do it with all my toys. I have a 2007 Polaris ATV that I keep in the garage on my hunting land up north. It sits for months without running and the battery is still like new because it is always plugged into a tender. It's the original battery that was in it when I bought the ATV new in 2007.

When I come back from a ride my Harley is plugged to a tender right after it's parked in the garage.

 

If your battery was fully discharged, then the charging time you mention seems about right.

If you have this global charger:

http://www.harley-davidson.com/gma/g...bmLocale=en_US

you don't actually need any other maintainer. The description says that this is an automatic charger and maintainer and will switch to a maintain mode when the battery is fully charged.

There is another post that I made a few days ago that discusses fast charging a battery. Generally 1.25 amp is a good charging rate to use on most motorcycle batteries. A larger battery such as those in some of the touring bikes could take up to around a 2.0 amp charge. Charging at much more than 1/10 the capacity of the battery can cause permanent damage to the battery.

 

My battery has never had a tender on it, but then it is only going on six years old. Time will tell I guess. I do ride in the winter some, and it rarely sets over a month without riding.

 

+1 on tender. slow trickle charge and maintain. every time it's parked.

 

I inadvertantly leave my GPS on occasionally = dead battery after a day or two. Slow charging usually takes at least overnight with my batter tender. If I need to ride NOW, I'll pull the seat and jump it. In the winter I use the tender all the time.

 

And if you're in a hurry, AGM batteries can be recharged at 10 amps in about an hour.

Otherwise, both the bike and the tractor are on Battery Tenders full time.

 

I always keep my bike on a tender. I originally bought it for winter storage but after reading many things here I just always plug it in after I ride. I'll even take it on long trips with me.