Wondering if a battery tender cable will tend to drain the battery when not being ridden...The battery is only months old and a stock Harley battery at that.

I bought a battery tender for 04' Road Glide and hooked up the leads on the battery one day. I went to wash my bike and shortly after I was finished, my bike wouldn't start. I was getting the click of death from a dead battery. I began to worry as I thought water got into some place where it shouldn't have been. So I waited a day and let it dry. sure enough when I try to start the next day it still wouldn't start. I test the voltage on the battery was drained down to about 11 volts. I took the battery out and got a load test on it. The load test was fine and I charged the battery and threw it back on the bike. Bike started fine. Two days later, battery was dead again.

*Ruled out a bad battery (brand new)
-cleaned the contacts on all the leads
-tightened down all grounds
-checked all fuses
-checked for stray voltage but only voltage was coming from the main fuse port. (don't thing the alarm would drain the battery constantly over 5 days)
-Stator tests good

The only other thing I could think of was the battery tender cable I attached to the battery two days before I washed it. Will it normally drain the battery? Had it on just so I could plug the bike into the charger in the garage once a week. Had a similar issue with my V-Rod and thought the quick disconnect battery tender wiring harness may be to blame by slowly trickling power out. What do you think? Anyone with this same issue?

 

I don't see any mechanical reason a tender pigtail can drain a battery. I would suspect a connection issue or a bad battery.

 

I had a similar problem and it turned out to be a bad cell in a one year old battery. Most of the time it would start, battery tender showed green but the click when starting sometimes

 

If the tender pigtail is not plugged into anything, it wouldn't drain the battery. Sounds like either a water short or a bad battery cell.

I've used the same battery tender (and pigtail) on two bikes with no problems. The last battery (EOM) lasted 7 years and was only replaced as a preventative maintenance item. It's still alive in a lawn tractor.

 

The BT cable can't drain the battery...unless it's been shorted. If the Battery cables and grounds are all good, then either the battery has a bad cell, or there is a parasitic load draining the battery.

The alarm load is very small and won't drain the battery.

If you have an ammeter see what kind of load you have when the bike is sitting idle...then trace the source by removing fuses one at a time.

 

I took the battery tender cables off the bike and for the last two weeks, no power has been lost in the time being. The cable work properly and charges the battery, but unless the cables were not attached properly, i don't know what would have done the draining. I did notice that a small amount of power was being pulled through the main circuit when the battery tender was hooked up. Significantly less (almost no power came out) when i disconnected it. That clearly shows that the BT cable was the source of the problem even though there was no sign of the cable being bad.

 

I noticed a few years ago when our power went out during a storm that the BT appeared to drain my battery slightly. Once the power came on all was fine again. You aren't by any chance turning the power off while the BT is hooked to the bike are you?

If this is not the case then I'd recommend getting a new BT pigtail. They aren't expensive. Check the old one to make sure it wasn't pinched by the seat, etc..

 

That little rubber cap should fit tightly on the plug, to prevent any voltage from spilling out.

 

I forgot about that. I have my BT on a shelf over the bike. The wire hangs down the wall and stops right next to the bike. I've left the cover off of the wire a couple of times and it drained the BT. I had to take the BT to the gas station and have it recharged. Thanks for pointing this out.

 

A simple check with an ohmmeter will tell if the cable is bad.