430ex ii Speedlite slow recharge on Canon 600D

Hi all.

This is my very first post - so please bear with me, if I've created this thread in the wrong category.

I'm a beginner to photographing. My partner (well, I'm her assistant) told me to buy a Canon 600D, a 50mm lens and the 430ex ii speedlite flash.

When I shoot in auto mode, the flash works and never misses a shot even though I shoot 2 images per second or so. The problem is that the shutter speed is at 60 and ISO is 1600. (these were the automated settings last time I tried. It was 30 minutes 'til sun down). This gives me blurry images. I'm going to shoot at mostly weddings so this is a big problem.

If I shoot on manual settings my shutter speed is 100 and so is ISO. By using these settings, the flash doesn't always work. It takes up 3 to 4 seconds. That's too long.

What can I do to make the speedlite work every single time on my own manual settings?

The problem with automatic settings + flash is that the camera sets the exposure for ambient light (ie: without the flash), which, in dim light is useless. In good light you can use exposure compensation to decrease the ambient, and let the flash provide the remaining light.

In manual, it will meter based, and then determine how much flash power it needs to fill in the missing light. The faster the shutter speed, the lower the ISO, the the bigger the aperture f value, the more power it takes. If you make the flash use too much power, it needs time to recharge. There are two solutions to this. One, use a higher ISO. This way, it takes less power to illuminate the scene. But keep it lower enough (or use a high enough shutter speed) that the ambient light doesn't cause issues. Two, use batteries that can spit out power faster. I use Eneloop Black batteries. Alkaline batteries tend to output power just fine at first, but then fade and output less power. Think dim flashlights, etc. That missing power translates to a longer recharge time on the flash. There's even a handy chart.