So looking at the example I linked to and what  the original post was trying to achieve, this code works for opportunities in my dev environment...

First the batch - there are two constructors, one that receives a Set, and one that is blank to execute all records

When we call the batch, you can either specify a set, and so limit the scope, or it will execute the 'full scope' SOQL when the Set is null.

global class CalYearEndBatch implements Database.Batchable<sObject>, Database.Stateful {

    //Query for OpportunityContactRole records with related Opportunity data.
    String query;
    Set<Id> soppids {get; set;}

//Constructor that receives set    
global  CalYearEndBatch (Set<Id> soppids ) {
this.soppids = soppids ;
} 

//empty constructor
global  CalYearEndBatch () {
}  
    //Execute the query. Check if set is null and execute SOQL accordingly
    global database.querylocator start(Database.BatchableContext BC) {
    if (soppids == null ) {
    return Database.getQueryLocator([Select Id, Amount from Opportunity order by closedate desc limit 10 ]);}
    else {
        return Database.getQueryLocator([Select Id, Amount from Opportunity WHERE Id IN :soppids ]);}
        }
    
    global void execute(Database.BatchableContext BC, List<sObject> scope) {
    List<Opportunity> opc = (List<Opportunity>)scope;
    for (Opportunity op: opc) {
//execute any code you want to as normal    
op.Amount = 888;
    }
    update opc;
    }
    
    global void finish(Database.BatchableContext BC) {
    }
}

To call batch with a set:

Set<Id> testids = new Set<Id> ();

for (opportunity o: [Select Id from Opportunity where closedate = LAST_YEAR]) {
testids.add(o.Id);
}

CalYearEndBatch cyBatch = new CalYearEndBatch(testids);
Id batchprocessID = Database.executeBatch(cyBatch);

 And without:

CalYearEndBatch cyBatch = new CalYearEndBatch();
Id batchprocessID = Database.executeBatch(cyBatch);

Hope that helps!