connected my cahrger and it's reading 'desulfate'...??? do I need a new battery?

 

YES...once a battery has "sulfated" the charging plates get a " shell" and will not hold a charge for very long or at all. Your F4i uses a maintence free battery (sealed) and is unserviceable, some other types that have the caps need to have the fluid checked occasionally, by adding DISTILLED WATER ( available at the grocery store)..if you have a battery that has the caps and you add tap water, that water has minerals and chemicals which are not good for the battery.
So for the F4i you will need to get a new battery...
When you get the new battery it will be dry, meaning the acid isn't installed. It will come with an acid pack ( looks like 6 plastic test tubes connected together with a black plastic cap/strip) take the black strip off the battery pack, put the test tubes on the battery and allow them to drain..

VERY IMPORTANT for longer battery life...with the strip still off the battery ( the strip is the cap for the holes you are draining the acid into) CHARGE THE BATTERY BEFORE INSTALLING THE STRIP AND BEFORE USING IT!!! If the strip is installed the battery is sealed and cannot vent, possibly exploding during charging!!!

And if you just fill it up and install it in your bike; you are doing yourself a huge dis-service!! The battery needs to be intialized for long life. Once the acid hits the charging plates the battery will have a static charge ( enough to do the job of starting the bike and such) but once that battery is put under a load, that is the "memory" the battery has and it will never charge any higher than the static charge...so charge it BEFORE using it and you will get much longer, stronger battery life!!