On Tue, 14 Nov 2006 02:30:09 GMT, Tom Kendrick
wrote:

650 amps at 12 volts is 6500+1300=7800 watts of power, DC.

I don't think a 650 CCA battery puts out 650 amps at one time.
Everything would melt.

To the OP, I don't think it is called a converter unless it goes from
DC to AC. From AC to DC it is called a rectifier, even if that is
only part of it.

....

On 13 Nov 2006 17:50:52 -0800, wrote:

Hello, I use a 12 volt winch to pull my boat up on a marine railway at
my seasonal cottage in Canada. I do not have permanent AC power to the
location, but can get a big enough extension cord to it if need be. I
want to buy a more powerful winch which requires a battery rated at "12
VDC - 650 Cold Cranking Amps" which is not a problem. I would like to
buy a back-up 12 volt AC to DC converter to power the winch if the
battery fails. Please advise on how to rate the converter based on the
battery requirement. Much thanks! D. MacQueen.