RP Series models with the "E" model designation come with a battery start option (RP6500 E, RP7500 E, RP12000 E). The easiest way to test the battery is to try starting the generator.

We recommend you start the engine on your generator once per month until it reaches normal operating temperature (about 20 minutes). This should suffice to recharge your battery if needed. 

For the RP6500 E and RP7500 E: If your generator does not start with the battery start option, try to start the generator manually using the recoil.  If it starts with the recoil, your battery most likely needs to recharged or be replaced.  

For the RP12000 E: We recommend the trickle charger be attached to the unit during storage between monthly testing to keep the battery maintained at the proper voltage. If the trickle charger is not on the unit for an extended amount of time and the battery has dropped below an adequate voltage to start the unit, plug in the unit for 24 hours and try again. If the battery still has not charged sufficiently, remove the battery and connect it to an automotive style bulk charger rated for 12V.  If the generator still won't start, you may need to replace the battery.  Contact your local Authorized Service Center for help.