There is nothing harder on a lead acid battery than sitting partially discharged, the sulphur in the electrolite slowly falls to the bottom of the battery and eventually shorts the plates together. A non float charger keeps the voltage too high as mentioned above and boils the water away. I bought the Battery Tender Plus because it specifically states that it maxes the battery then drops to a slightly lower float voltage.

One thing I'm careful about is to wait until the day after a ride to attach the BT rather than connect it to the battery while its hot, that's providing I'm not going to ride it the next day.
The BT is visible on the wall above the bike.

 

Things running when bike is turned off,point to corrosion at fuses and relay,need to be claened and dielectric greased.

 

I have a 07 Nightster,bike is in shop now for efi issues, at times,after parking the bike,engine off,key "off"and out,theres an odd light sound coming from efi module area,if I place the off/run switch to the run position it will stop.somtimes it can be many days later b-4 it happens again..bike is in shop now,setting there,and.....not making this odd noise..I guessing a shrt in the switch?

 

08 nightster with less than 1K. Just got out of the shop where it sat for 35 days trying to figure out why the battery was dieing. turns out the speedo was drawing to much power. They ordered a new one which of course was wrong and the fuel light stayed on then finally they ordered the right one. They said they had four more bikes come in within the next week or so with the same problem. I guess a bad batch of speedo's

 

I've had EFI bike for nine years and never used a tender. My first battery was replaced at 5 year/52k miles outta paranoia. It still passes a load test. The second one is still in the bike. Sometimes, she sits for a month or better and still starts the bike. The EFI bike that I ride at work is a 2003, along with the others and still have their original batteries. They sit for months at at time without being ridden or on a tender and never fail to start.

 

once you get the fuse block wet and corrosion sets in the 2 relays can go bad. I just had my bike in the shop , they cleaned it out , greased it and then i got it home and 5 days later the EFI starts acting up. does not pressure up when bike is turned on. yellow engine light eventually did not go out. took it back and they put in a new battery and a new replay and it runs like new now. you can also tap on the relays to get that noise to stop. I also am waiting on the dealership where i bought it to call me. i have been complaining about this problem for a while and they said they contacted HD and HD has a new wiring harness for me to replace the POS one that came with it. So i would advisse anyone with this problem to keep complaining and get the new wiring harnesss, which i hope is redesigned, before their 2 year warranty expires. i am going to post pics of the new one once i get it.