This comment is from else where on the web and is similar situation.
"The car must NOT draw 1amp continuously, this will flatten the battery in a couple of days as my earlier calcs show. However, you need to get the current drawn test done for at least 1 hour, since some systems run for a while after the car is locked up. (eg: my Satnav draws 600ma for exactly 1 hour, then drops to 12ma for the next 72 hours, the 2ma after that)
Once you have confirmed that the car is remaining powered up for an hour or more, it would be useful to pop out the fusebox fuses one by one until the current draw drops from 1 amp to a more 'quiescent' value. This will then at least tell you which fused circuit it loading the battery, and will help you to narrow down the culprit.
Then, once you know the fused circuit that is causing the grief, you unplug each device that is serviced by that fuse, one by one, until you find the offending part. Then you smash it into little tiny pieces and fit a new one".
Basically, there's merit in what he's advising it can be something other that the RNS510 on the same circuit not allowing the car to change to its quiescent state - should be less than 0.1 amps after 25 minutes when the keys removed!
How long have you had the RNS510 fitted and does it have the correct Can-Gateway to prevent battery drain?
