Before wings hit I was really bored and experimented with several ships, distributors, and Shield gens, testing recharge times and rates. I came to a fairly consistent conclusion but didn't have quite enough data to back it all up. The conclusion was that there are 3 different recharge times for shields (in this case downed shields) 1st- There is a ~16 second buffer time before the real recharging begins, this is ~16 seconds on every ship with every known configuration. 2nd there is an elevated recharge rate from nothing to half full, during this time the shields are still down, as you all know, but also during this time the maximum rate of recharge is between 1 and 1.05 MJ/s. 3rd stage is normal recharge, this is also fairly consistent across ships and lands somewhere between .6 and .65 MJ/s max.
The way shields recharge is that they only draw power from the capacitor, and they draw power at the above given rates (1 and .6 MJ/s). The capacitor is charged from the power plant via the distributor at a rate correlating to the # of pips in SYS, as well as the base stats of the distributor (if the in-game stats say 1.2 MJ/s, they refer to 1.2 MJ/s as the max rate with 4 pips. at 2 pips it's half this amount... all rates correspond to the number of pips in a direct linear relationship now.) Now this being said if the capacitor is depleted, shields recharge at the rate of capacitor recharge, again, which is determined by the stats and pips.
This is a bottleneck for all ships. I don't necessarily agree with it and would rather that better distributors charge shields at a faster overall rate. Because shields charge in a way much differently than weapons and engines, they added this hidden recharge rate in order to visualize the actual charge speed. If the power out was the same as the power in, you would never see the bars in the capacitor actually go anywhere. This also allows you to charge the shields with no pips and a full capacitor, even just a little.
For the above statement- Turn off shield boosters to get your shields up quicker. I think it depends. Because your shields are recharging at a faster rate I feel like you should keep your boosters powered in order to take advantage of this faster rate, and avoid having them charge up completely at the normal slower rate.
Edit: I also used a stop watch and timed the different segments of recharge, several times for consistency. For ships with small distributors (that have maximum rates of .6 MJ/s) I kept full pips in SYS, this way even though the capacitor would drain during part 2, and stay relatively stable during stage 3, It would begin to increase when shield recharge was finished. Often times the hardest part to recognize is when shields have finished recharging. As far as I know this is the only concrete way to determine shield recharge completion but it still may be off by as many as 1 or two seconds, while at least one bar is recharged in the capacitor. If anyone else has another way to determine this, please let me know, It'll help me out with further tests.
I also did some tests for Shield cell banks as well in order to find out exactly how much MJ of power each has, and they seem to have the same amount of power despite being on different ships with different configurations. I'll do more testing on this in order to come up with slightly more accurate numbers in the future but the findings are fairly consistent.