They will never be matched in any case as obviously they are themselves made
of cells in series and each one will have slightly different capacity. When
any cell goes down, it is reverse charged by the current flowing through the
load and the impedance rises as the voltage drops, so to speak. I used to
use these batteries in models and really all one could do was try to catch
the voltage dropping below the norm and then recharge them both.
Brian

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From the Sofa of Brian Gaff Reply address is active
"Adrian" wrote in message
...
On Tue, 13 May 2014 04:54:43 +0100, Bill Wright wrote:

Given two 12V lead acid gell batteries, both new, both the same type,
but from different sources, how do I balance the charge before fitting
them in a 24V appliance?

Chuck 'em both on the same 12v smart charger until they reach "float"?