Ian Johnston wrote:

On Thu, 21 Apr 2005 11:07:23 UTC, Ronald Raygun
wrote:

: What exactly happens at the microscopic level may well be complex and
: diverse, but the current passing through any surface you'd care to cut
: through any cell will be the same.

Is that strictly true?

Yes, I very much believe so, and know of no reason why it should not be.

When a cell is charging, with electrochemical
processes taking place at the plates, does the charging current still
exist between them? It wouldn't in a capacitor, though I suppose the
displacemet current would even up the score a bit there.

That's because in a capacitor the dielectric replaces the electrolyte,
and the energy is stored in the form of an electric field created by
the physical separation of "real" (electric) charge.

In a battery no electric charge is stored at all (to speak of) and
energy is stored by chemical changes to plates and electrolyte.

Out of every two SO4-- ions in any drop of electrolyte, on average one
travels to each plate, but all four corresponding H+ ions travel only
to the PbO2 plate. As I tried to explain yesterday by considering the
drops laid end to end in series, this means that for each two electrons
travelling left to right on the outside, the charge balance in each drop
of electrolyte is neutral (-2 out to the left, -2 out to the right, +4
out to the right) and at each inter-drop interface this means charge
travels either -2 left or +2 right, plus self-balancing through traffic.

Hence charge travels on the inside as well as on the outside.
Where charge travels, that's current.