I've had so much trouble with knock off batteries from ebay. I finally ordered an 1800mah OEM battery, but havent received it yet. I also ordered a 3600mah battery but it's total junk and lasts barely as long as a regular oem battery. Is there anything OEM that's larger than 1800? Any suggestions? I don't care how big it is (physically) I just need the longest life possible when I am out on my motorcycle with no car charger. Thanks!