Battery Problem

[gjd]

Hello

I've been using my N97 Mini since Jan '10, and I still think it's a great phone.

BUT - my beloved N97 has developed a fault, and I can't fix it. This has happened suddenly, in the last week or so. I haven't changed my usage habits, or downloaded any new apps.

The problem:

Every night I switch it off, and plug in a genuine Nokia charger to charge overnight. When I switch on in the morning, the battery indicator shows "full".

All is well for around 5 hours or so, with the phone showing all 7 battery bars. Then, suddenly, it drops to one bar, and I get the low battery warning. Then the phone dies.

The attempted solutions:

I tried to find Nokia's battery monitor, but it's been updated for Symbian 3, and won't work on the N97 any more.

I bought some genuine BL-4D batteries, and tried replacing the original battery.

I tried a hard reset.

The problem hasn't gone away.

Any thoughts?