The code looks like it has an issue... you have:
$UpdateQuery->bindColumn("Batch_Date", "t", "".($rsBatchRecords->getColumnVal("batch_date")) ."", "WA_DEFAULT");
$UpdateQuery->bindColumn("Completed", "c", "".((isset($_POST["Completed"]))?$_POST["Completed"]:"") ."", "WA_DEFAULT");
$UpdateQuery->addFilter("Batch_Date", "=", "t", "".($rsBatchRecords->getColumnVal("Batch_date")) ."");
The first thing I see is that you have "batch_date" and "Batch_date"... only one of these is correct, or maybe neither since in the query you have "Batch_Date"
I think you want:
$UpdateQuery->bindColumn("Batch_Date", "t", "", "WA_TIMESTAMP");
$UpdateQuery->bindColumn("Completed", "c", "".((isset($_POST["Completed"]))?$_POST["Completed"]:"") ."", "WA_DEFAULT");
$UpdateQuery->addFilter("Batch_Date", "=", "t", "".($rsBatchRecords->getColumnVal("Batch_Date")) ."");