Out of the blue my 2009 CRV diesel started suffering from a completely flat battery every morning.I had battery and alternator checked free of charge at my local tyre /exhaust centre.Both checked out ok but fault continued.I then passed my car onto my local Honda main agent who carried out a diagnostic check on my vehicle at a cost of £51.They could not find any drain on the battery even after 24 hrs.Sure enough the day after I picked it up the battery failed again!!.To cut a long story short after searching through numerous Honda forums I tracked the fault down to a faulty air conditioning relay.
At a cost of £21 for a new relay and a five minute job to fit it I have had no further problems.If anyone has the same problem the relay is in the fuse box mounted to the rear of the battery.It is a black plug in block that can be removed by hand[or with pliers if tight ].In my case there appeared to be something loose inside.On breaking open the relay I found a small diode adrift inside.I believe honda are aware of a problem with these relays and have now changed their supplier.I hope this is of help to someone even if it was a bit long winded.

 

welcome to the forum. Good find and fix. Thank You for the information.