T i m Inscribed thus:

I've since ordered an external charger that should be ok for most of
the Dell batteries so at least I can prove if it's the battery or
the laptop.

They put these "one wire" interfaces into the batteries too !

No, really? ;-(

So I understand.

I've had cheap Chinese made ones that wont charge in a Dell !
Which sounds a bit like the one you refer to above.

It does indeed. However, after Googling about it seems there may be
some hope in a BIOS update? It's currently A2 and I think there is an
A5 or 6 to be had. I just need a charged battery in there to do it.
I've ordered an external charger as I'm told the pinout of most of the
Dell batteries are the same

Yes but they put the connector block in different places on the battery
pack ! You will have to let me know how it goes.

(so it will cover a fair range of models
and we have a few between us) in case I can't access another machine
or a charged battery elsewhere.

Might as well do the easy / non-invasive things first. ;-)

Cheers, T i m

I couldn't agree more.

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Best Regards:
Baron.