How frequent do you have to use powered rails uphill?

How frequent do I have to place powered rails to keep climbing at full speed?

Some people say that you only have to use the same amount from powered and non powered, but you can do like 3 powered and 3 unpowered. This is not true, I tried that out. The best way seems to be switching between powered and non-powered (one powered, one non-powered, one powered, ...), which brings a big waste of redstone torches with it. Any other ideas? I didn't test it enough to prove it.

This is NOT the same question as this one here. I ask specifically for full speed and not "minimum of powered rails/maintain reasonable speed".

The ratio of normal rails to powered rails depends on the speed the minecart is already moving. For the sake of the question, however I am going to assume that the minecart is starting and going immediately uphill in which case (as of 1.9):

powered rail = + normal rail = - repeat = \

-if you press the "w" key the whole way: +--+--+--\

-if you don't press the "w" key the whole way: +-+--+-+--\

This is assuming that you are transporting a player, otherwise the answer is completely different.

P.S. Yes, this is for maximum speed