I have a car battery charger, and my bike battery is at about 7 volts. I've used the charger to charge a maintenance-free car battery. I had it set to "10 amp" and "maintenance free/deep cycle."
The bike battery is a low maintenance battery, so I set that switch to "low maintenance." However, I wasn't sure what to put the amp switch to. Possible settings are 2 amp, 10 amp, and 50 amp "starting power." I would assume 10 amps, but I'm not positive.