Canon 580 EX refiring is Very slow....missing some good portraits of kids when I see they are underexposed or not exposed. How do I in erase refining rate. Batteries are new. Do I need to I crease ambient light?

SOURCE: Recently my canon speedlight 580 EX II TTL has

that the camera/flash set-up I use ... there are many variables - iso/metering setting/shutter settings/flash settings .
If it's a flash function problem, try this to isolate it - first, with the diffuser/reflectors tucked into the flash head, and the head straight up, with the flash set in master mode, turn it on and look on the back screen. push the mode button til you see the ETTL in the upper left of the screen .. then press the set button in the center of the dial and the nuber in the center of the display should flash (+0) while the light is flashing, rotate the dial to change the setting (i usually under power by 1/3 stop. Play with the exposures a few times to get the feel for what the EV shifts do to your exposure. generally speaking, for interior low-light, i prefer to bounce off the ceiling (if low ceilinged), if there's too much direct it will give you an uneven and predominantly underexposed image.
if you prees the mode button you will come to the same options for adjusting the output in manual mode, but it will not work with the autoexposure in the camera.
Try playing with the ETTL settings
I think the problem may be that you have somehow altered the power output setting on the 580.

SOURCE: I have recently shot some pictures with my canon

It all depends on the environment you're shooting in. When shooting a wedding reception for instance inside in the evening I will generally use ISO 800 and I quite often use FE Lock which is very handy. FE Lock will pre-flash the speedlite and meter the result based on the center focus point in your viewfinder (it doesn't matter if you have set another focus point it will always meter to the center one so make sure that is over your subject when you use it). To use FE Lock press the button near your thumb that has the * symbol with the center focus point over the subject. You can then re-frame the shot if required and take the picture. The camera will take the picture based on that flash setting and you should find that the shot is better exposed.

SOURCE: Amperege of 580 EX-II

Interesting Question!
The rating in milliamps is a matter of battery capacity and charging rates. The higher the better as you will get more flashes per charge as long as you have the correct charger to match the batteries’ capacity and use the correct charging times. Aside from this issue of duty cycle between charges- this has no effect on the power of the flash unit as to output. This cant burn out or damage the circuitry.

The issue here is VOLTAGE. Most AA alkaline batteries provide 1.5 volts. Most rechargeable AAs provide 1.2 volts. We are looking at a voltage differential of 1.2 volts (a 20% deficit) if 4 batteries are required. This MAY cause slower recycling times in order to attain a full charge for each shot. In SOME units that can cause a bit if overheating due to strain on the step up circuitry.

It so best to check with the manufacture or distributor of you flash unit before purchasing you rechargeable batteries and charger. If you units have a built in charging circuit this can definitely be problems if there is a mismatch in charging rates and voltage. If this is the case be sire to check your manual or with the manufacturer or distributor- there must be a list of compatible batteries.

Ed