Faced with a dead Nokia N86 that refused to charge, Steve Litchfield didn't panic - armed with the luxury of some of other devices to hand, he was able to get the N86 and its battery revived and working properly. And, in the process, learned that all Nokia's batteries are electrically interchangeable. Maybe these concepts will save the day when your precious S60 phone appears to have died?

Early Nokia firmwares are buggy - that's a given, in my experience - and the N86's is no different. I awoke this morning to a phone that appeared dead. Some rogue OS process or S60 application had been running away with the processor during the night and some bug in the firmware hadn't protected the battery by closing the phone down when the voltage got low. 

The result was that, even after taking out the battery for a minute (to let any remnant charge leak out of the electronics, that might be confusing the logic in the circuitry) and then reinserting and plugging in the mains charger, did no good - no Nokia logo, no charging animation - nothing.

First reaction: panic. Was the phone itself dead? Was the battery irretrievably damaged?

Second reaction: I'm fortunate to have other devices around, I wonder if any of them can help.

Now, the N86 uses the BL-5K battery, common only to itself and the N85, but I couldn't help noticing that the pin formation on all my Nokia batteries looked identical. Somewhat tentatively, I inserted a fully charged BL-5F battery from my N95 into the N86's battery bay. It just fitted 'vertically', although it didn't use all the available width. Press the power button and instant life - the N86 booted fine.

Proving that the phone itself was largely OK, which was a relief. But what about the BL-5K battery? I wonder if the electronics in a different device (perhaps of an older, more electrically robust generation) could charge it where the N86 couldn't? I couldn't charge it in my N95 since the battery bay was too narrow. Cue a hunt through my admittedly larger-than-usual device cupboard. 

I found my old Nokia E90, with the largest battery bay of any device, designed for the huge BP-4L. Again the pin connectors matched in formation and general position though, so I rested the BL-5K up against the contacts and inserted my charger. A beep and the battery appeared to be charging normally!

Had I saved the battery? I'd been worried that the charge had been taken so low that it wouldn't now work at all. But it seemed to be accepting charge again. An hour later, I took the battery out and put it back into the N86 8MP. Now came the moment of truth. Had the battery actually been charging and would the N86 accept it again and finish the charging process?

Yes!

So, things learned from this early morning panic and rescue mission:

• Batteries from one Nokia phone often fit (at least electrically, for diagnostic purposes) other phones
   
• Just because the electronics in one phone won't charge a battery doesn't mean that the electronics in other phone won't.

Steve Litchfield, All About Symbian, 2 July 2009