No limits set on number of votes (but Crowdsignal does automatically limit if you vote too fast, which I estimate at more than 25 votes with breaks under a minute). If you want to avoid getting limited, it might be safer to limit your voting bunches to a number less than 25.
Crowdsignal monitors by IP address. So if you and someone else in your household are voting using the same wifi, you are seen as one voter and your votes combine under the limiting blocks.
I can delete votes from bots on my end, so keep that in mind.