I have a Honda Prelude 1998 and if the battery is connected (with car off), after 2 days it is mostly drained. If I recharge it and disconnect the battery, it has a good charge even after 10 days (I know it has a good charge because the charger says so when I try to charge it, and also the car starts smoothly).
The battery is around 2.5 years old.
I have followed some instructions on testing a parasitic battery drain and with everything off, the multimeter is showing a drain of 0.02 (with multimeter set on 20A; I guess that's 20mA) which seems normal.
Is there any advice I could get on what to look at next?
Could the battery have a fault that manifests only when the battery is connected (considering the charge stays there for a long time if completely disconnected)?
I will have to do more testing to confirm, but at some point it looked like the multimeter stayed at 0.02 without any change, but after 30-40 seconds it went up to 0.06 without anyone touching anything in the car and then it went back to 0.02