Well, your voting bar recharges 20% each day and 20% is 10 votes... So if you havent been on for a week you can cast 10 votes at full weight that will be recharged the next day, or 50 votes that will be recharged in 5. But each vote gets successively weaker..
Once your rep goes up, your vote will have a greater affect on others rep, and you get a slider controlling vote weight at about 500 Steem Power.