each full power vote uses 2% . Vote power recharges at like 1% every 1.2 hours. You can get a vote slider when you reach like 500 SP or you can go on busy.org and they will give you a vote slider. Also if your vote gives out less than $.03 it gets rounded down to $0.00 at payout time so as horrible as it sounds you are wasting your vote power making upvotes on comments if you can't bang out a $.03 payout.

https://staging.busy.org/@thedarkhorse/your-2-cent-vote-is-worthless-the-real-deal-on-dust-votes