The fumes were something I was wondering about trapped under a cover.
No worries?

 

Just don't forget to Use-it , been use-in mine fur 6 years

 

BT Junior has my '04 battery still going. Direct connection to battery with pigtail always available after unplugging cover.

 

I used one on my '03 ultra with a cover. Never had an issue with fumes. I wouldn't do it with a wet cell battery tho. The fumes from charging it would eat the cover.,,

 

I have them on both my bikes, I finally changed the 03 battery @ 7 years old because I was going on a 1000 mile trip alone. Battery was still good just didn't want to be stranded. First thing I got for my 2011 Limited. I have never had any issues, seats on or covers on.

 

Have one on both bikes and even my riding lawn mower. The original battery is still going strong on my 2003 sporty since oct 2002.

 

Modern Harley batteries are sealed AGM pure lead batteries, so no "fumes" to worry about.
"Fumes" from older batteries (acid pb-ca batteries) are actually hydrogen and oxygen resulting from electrolisis of the water inside the battery. They are dangerous as they can explode if ignited (and the slightest spark is enough) but they are very volatile, so there's no risk of build up.
The only concern with modern HD batteries is that AGM batteries require their special tender if you also reload the battery, as AGM batts have a three-phase reload process, with constant high current, constant low-current and constant voltage phases.
Normal battery tenders load with constant voltage and may damage such a battery.

 

I would ring it to the battery. Just be sure to hook it everytime you put her up.

 

honestly, i wouldnt bother with one. never have used one. on any bike or vehicle. i am a firm believer in replacing batteries every four years, no matter what. i don't want to be stranded in the woods in my Diesel, or on the road on the bike. Both my bikes have cell chargers permanently wired to battery, and the HD has three red LEDS in the headlight, that all stay on when parked. it can sit for weeks and no problem starting. al the battery tender stuff just seems like a lot more trouble than its worth. i havent figured the cost to run the tender, cost of the tender itself into it, but i bet it runs more than putting a new battery every four yrs.

 

Two bikes and two cars, all wired direct to battery, all covered for the winter. I have never had any issues except last year one of the tenders (6 years old) gave up about half way through winter.