Aspire 5738z cooling fan runs long when on battery with custom low power scheme

Hi,

I have a 6mth old Aspire 5738z running Vista HP SP2 with all important updates applied. I updated the bios (to 1.19) as my laptop was one of those flagged as affected by the overheating power brick issue - although I'd had no issues myself. I am now running on BIOS ver 1.25.

I have created an aggresively low power scheme to extend battery life when browsing away from A/C power. This includes (amongst other things) throttling back the CPU max to 25% when on battery. I use this scheme when just wanting to browse the web wirelessly to extend the battery life and keep things cool and quiet.

This works fine for a while - often up to 30mins when the fan will come on and then stay on for an extended period of time. I haven't timed it but it's several minutes - I can believe 5 minutes easily.

However the CPU core temps are typically 31/32 deg.C when the fan kicks in and don't change. The exhaust air feels barely warm.

The fan never kicks in like this when on A/C power.

I haven't evaluated the standard low power scheme behaviour yet and I can't comment on if the behaviour was different on previous BIOS revisions as I hadn't tried to maximise the battery like this before.

I am aware of the throttling issues which may be due to faulty sensors/other and think this may be a correlated issue except for it only happens on battery.

My "concern" is that long fan run times are just sucking battery power and apparently unnecessarily in this case.

Anyone else experienced anything similar have any ideas?