I'm 87% sure it's a 11mm nut, I used a 3/8 ratchet with a long handle, shallow socket and a short extension (3"ish long). Use a universal joint at the socket to make it a bit easier. Once you break it loose you can unthread it with your fingers, it's not a lock nut.

 

I use a 7/16" socket on a 3/8" short-handled breaker bar (because of the angle head). Doesn't take up much space in my emergency roadside toolkit.

 

The difference between 11 mm and 7/16 inch is about .005 inches or 0.11 mm, so you can use whichever is convenient to hand and the right height.

 

I couldn't get a socket on my '04, managed with an open wrench, forget the size - took a while, couldn't get much swing on the wrench. If your ground cable runs into the back of the battery box like mine, you could do what I did, get about a 4" longer cable (as someone already suggested) and route it into the front of the battery box - then you can just undo the positive cable, pull the battery out and take the ground off the battery, no more messing with that hard to reach stud on the case.

 

Or use a battery tender?

 

I have 7 batteries from stuff in the garage and the shed out back; no electricity for the shed, and I probably wouldn't switch the 3 tenders I have as often if I had to mess with them below zero. Figure it's probably easier on the batteries to have them in the warm anyway, and this way they don't go more than a couple days without getting a green light on a tender. With that mod, it's simple to pull/install the 1200battery, and all the rest are already easy. Thinking of getting a couple more tenders so the Harley batteries can stay hooked up all the time, though they've been doing fine this way.

 

You might just permanently hookup a charging pigtail so the charger could simply be plugged in. Same cord might be used for heated gear or charging a phone.

 

Hi, I had a similar problem when trying to replace my battery. After hours of trying, no tool combination (well, the ones I had available to me) would seem to reach the ground bolt on the engine case. A google search yielded the idea of pulling the main fuse allowing the battery cables to be removed in any order without causing sparks. Worked fine for me, it took a little bit of fiddling re-installing the negative cable first before sliding the battery all the way back in.

 

You would think they could make the cable 1/2 inch longer and don't you just love the little brass spacers (non magnetic of course, the harder to retrieve) and the floating nuts in the battery that always manage to fall down into an almost impossible to see and get to place in the bike. HD engineers suck.

 

I have pigtails on both my bikes. The '07 has 2. One for the tender/GPS and the other for my heated gloves.