Bridge rectifiers

Although bridge rectifiers are not something normally associated with computers, the fact that the OC community is comprised of many individuals who have a greater understanding than I do of electrical components and their applications, I thought that posting my question here just might be the ticket.
The question I have is how one determines the voltage rating requierment that a bridge rectifier must be. I have a rectifier that I know is rated at 20 amps but I do not know what it's voltage rating is. The rectifier is used on a non-regulated power supply. AC current being generated is 180 to 200 volts. The rectified DC current must not be higher then 14.5 DVA. The 14.5 DVA is to charge a 12 volt lead acid battery. I believe the rectifier is faulty because voltage going to the battery is 17.5 volts which to to high. Is the rectifier required then rated at 12 volts and 20 amps capacity. Or, must the rectifiers voltage rating be that of the AC voltage being rectified. I have checked websites of manufactures/suppliers of brigde rectifiers and have only seen brigde recitifiers with ratings of 20 amps with 50 volt, 100 volt, 200 volt and 400 volt ratings. Is it the voltage of the battery that regulates the output of the rectifier. If so is the 17.5 volts reveal the fault is with the battery and not the rectifier?

when i built a powersupply in electronics class, (w/ bridge rectifiers) we used a step down transformer 120=12VAC, then did the rectification.

The rectifier just turns AC into DC, and is rated for that voltage. So the transformer determines the voltage that the rectifier operates at. A 50V rectifers should work fine in your case, if I understood your case correctly.

So it's not the rectifers fault if the voltage is too high, it's the transformer. But getting the right voltage without some sort of voltage regulation is hard. Unloaded the rectified voltage will be roughly transformer voltage *1.4. Under load it will drop, can even drop below transformer voltage.

The high unload voltage is due to you only seeing the "peaks" while AC is measured as an average. As you draw power, you get to that average, but the rectifiers turn-on/turn-off delay gives another slight drop in voltage..