On Thu, 2005-11-17 at 09:01 +0000, Chris Green wrote:
A bigger battery won't take more charging current, it'll just take longer to charge. The internal resistance of just about *any* lead acid battery will be negligable compared with that of the charging circuitry, the charging circuitry will set the current at any given voltage and will not be affected by the (negligable) internal resistance of the battery.
I think you may be confusing the charging of lead acid cells with dry cells.
Ideally lead acid cells should be charged with constant voltage not constant current as with most dry cells (actually is not as clear cut as that as some of the more modern dry cell technology requires a sort of constant current/constant voltage hybrid charger that switches modes at different points in the charge)
My point is that a badly designed battery charger for a small capacity lead acid pack could feasibly become damaged by operating beyond it's rated output duty cycle by being connected to a larger capacity pack.
A lot of the better UPS's have smart charging circuitry that cycles the battery (not a deep cycle, just a gentle charge/discharge) and monitors the battery condition based on results from this cycle. I could imagine it getting a little confused if a larger (or otherwise different) pack was connected.