I'm not sure about changing the recharging algo, but I've had similar thoughts for the points system: e.g. buttons of +1, +10, +100, +1000, etc where each button represents a multiple of 1M rshares.

This way you could give consistent votes to posts and not have to factor in voting power unless it's drained too far (at this point, the higher-vote buttons would start to get grayed out). Also, such a feature would make it easy for whales to stay under whale-vote threshold by giving precise control.

Also, as users power up their account, they get access to more buttons (or the ability to grant more of each). The UI could display how many of each 'megavote' they have remaining, along with a bar showing vote power %.

Users would quickly see how bigger votes deplete their power faster. And they would easily & visually see how powering up gives them more power.**

** especially if powering up instantly boosted your voting power. e.g. if you have 100 SP and 0% vote power, when you power up 100 SP it should instantly boost you back to 50% vp.