I use battery tenders on my older Porsche and on my '04 Low Rider. Here's how I set up my H-D.
First, I purchased and installed a Powerlet Harley Mid Kit
http://www.powerletproducts.com/products/harley_mid.php
This particular method of setting up a weather proof powerlet plug allowed me to install the plug on the horn mount, which ends up looking like H-D itself designed and put it there. I like this better than having a wire & plug dangling loose on my bike.
Then I purchased a second Porsche battery tender. The reason I like Porsche's tender is because Porsche hot-wires their cigar lighter so it's hot @ all times, thus allowing a battery tender to be connected by merely plugging into the female lighter socket and because the Porsche tender has a charge setting for either cars or motorcycles. Here's the charger I use:
http://e-partssales.com/Merchant2/me...Code=986engele
I like this setup and thought I'd share it here in case someone else might be interested in this different approach.
JB