Thanks for your report. The entry is not wrong, the term 'balance' has been used in English since the 13th century to refer to the weighing scales. Originally the 'scales' were the two pans on the balance.
In modern English there are still some expressions in current use where Port. balança is translated by Eng. 'balance', for example: balança de pagamentos > 'balance of payments'.
I've made a little adjustment to the entry to clarify this.