I can tell you that most of us a smart battery charger such as the Battery Tender (there are specific models for gel batteries) and plug them into the "Powerlet" accessory port. The port wasn't standard on the R's (not sure about Rocksters) and IIRC the powerlet connector for the end of Battery Tender cable is a separate purchase, but well worth it.
There is an inexpensive bmw socket you can buy for the site (there is a blank plug there now). The r1150r is pre-wired for the port. Most people use this port to charge or battery tend.. If you are not going to use a unit with a bmw plug, buy an extra lead so you can adapt it.
Here is an excerpt from our tech tips page:
Tex writes: "My R1150R did not come equipped with an accessory plug. Part from Bob's BMW was $27. The plug goes into the plastic cover on the left side of the engine just below the fuel injector body. Only one allen head screw secures this cover on its trailing end and then the cover can be pulled back and out. The plug then screws in place of the black plastic coverplate. There is already a power jack that is factory prewired. This is a male plug that is tied on to the solenoid wire and tucked up out of the way. I needed to use a flashlight just to find it because it was behind the bundle of wires above the solenoid. Cut the cable tie securing it to the solenoid wires to give it some slack and then pulled it down to plug into the female end of the accessory plug. Reattach the cover plate and you are done!"
1. Install the positive terminal post so that you can jump start the bike without disassembling the tank to get to the battery. If you don't want to do it, then let your dealership do it. The part is dirt cheap and the labor is easy.
2. The trickle charge battery tender can be had with a BMW power outlet adapter to plug directly into the power outlet.
On the Rockster, the BMW power outlet is suppose to be standard equipment, but some of them come without thusly equipped. Mine came without and I insisted that the thing be installed under warranty and that's what the dealership did.
Cogito Ergo Vroom - I think therefore I ride.
03 Rockster, 07 Aprilia Tuono R, 07 KTM 990 Adventure
if the outlet is only 29$ then i'll just pay. i have a tenuous relationship with bob as is due to my blulnt honesty on one of those post-service telephone surveys!
The part is cheap, but I'm sure that they'll ding you for labor. The hell with that. If the bike were suppose to come with the power socket, then it needs to be equipped with the power socket. Let Bob's BMW or whomever your dealership is deal with BMW Motorrad USA as a warranty issue.
I bought my bike in New Mexico at Motorsport of Albuquerque. But then I moved out to California and got hooked up with Irv Seaver BMW and noticed that I was missing the power outlet. I called up Motorsport and they consulted with their BMW rep and came to the conclusion that it's a warranty issue. I called up Irv Seaver BMW and talked to their warranty guy, showing him the BMW website with the standard features list showing that the power outlet is suppose to be there and I mentioned to him about my conversation with Motorsport. So we got the bike set up for installation.
Later on, the Irv Seaver service manager was mentioning that it wasn't covered under warranty and I had him chat with the warranty rep. I said that I don't ask for anything that extra on the bike. All I ask is for BMW Motorrad USA to authorize its dealership to bring my bike to THEIR specs. No more no less.
Cogito Ergo Vroom - I think therefore I ride.
03 Rockster, 07 Aprilia Tuono R, 07 KTM 990 Adventure
Mine did not come with the accessory socket and the $95AU price tag has put me off buying one. None of the Australian accessory plugs actually fit into the standard euro socket anyway!!
Is there a terminal post kit I can install so I can charge the battery without removing the tank ? (my friend's R1200CL has these).
I Feel Cheated if it was a Warranty Item!! I Paid Extra To have Roman's Cycle shop In Ohio, Install The socket! 
