I believe the actual voting algorithm is relatively simple. When you vote at full strength, (100) the vote uses 2% of your remaining voting power, no matter what you are at. So for example if you have full power and vote once, then you're at 98 (2% = 2). However if you were down to a voting power of 50 and voted once, it would drop you to 49 (2% = 1). It is actually impossible to vote yourself entirely down to 0 power because of this system.