Ok this is becoming a real problem.
Over the last few months the battery has run flat many times. If its left for a week or two its almost certainly going to be flat. But on top of that there are weird exceptions.
For instance this tuesday i jumped into it to goto the nursery, it had sat for about a week, and it failed to start. I jump started it and it drove to nursery (2 miles away), it restarted fine after nursery, then drove to the school (1 mile from nursery) and it restarted fine after the school, then i drove it home. I meant to put the battery on charge to give it a proper top up, but forgot. The wife got in on thursday and said it started fine. She drove it about town a fair bit on thursday no bother. Then on friday morning it was completely dead.
Put the battery on charge on friday evening (current limited bench supply, set to 14.4v 10A) and left it for 24hrs. When i checked it on saturday evening the PSU was showing it was still pulling 0.5A so i left it overnight. In the morning, still pulling 0.5A. So i disconnected the charger and dug out the clamp meter for some probing.
Immediately after opening a door, its pulling over 3A, quickly drops to ~2A. Shut the door and it drops to slightly under 1A for maybe 5 minutes or so, then drops to 0.35A and then just sits there. Even half an hour later its still drawing 0.35A.
0.35A feels pretty high to me? Certainly enough to flatten the battery over a week or two? Thats 8.4AH over a 24hrs period. Battery notionally holds 80ah, so 10 days is enough to completely flatten the battery with that load, and ofcourse it'll probably fail to start before its fully empty, and its probably no longer holding 80ah anyway.
But it doesnt feel like "BECM staying awake"? The BECM seems to draw about an amp when its awake, and you can see that after opening/closing a door, but it fairly quickly drops down to this 0.35A reading.
Anyone else measured what the car draws when off as a comparison?
Any ideas what might be going on? The battery itself might by dying, but that wouldnt explain this continuous load, and i dont want to replace the battery and kill the new one by continually running it flat!
It also doesnt explain why sometimes it lasts a week, and other times it doesnt even last 12 hours!