->  That will limit your current to less than 2 Amps,
-> assuming that you are getting about 20 VDC unloaded
-> and the output drops to about 12 Volts at the current
-> limit. If you are getting less than 15 VDC, the
-> current would be limited to less than 200 mA {at} 11 V.

->  Personally, I'd use a fuse of the appropriate value
-> when using the unit as a power supply (ie 2A fuse for
-> a limit of 2 Amps, 3A fuse for a limit of 3 Amps, etc)
-> and I'd use a light bulb to limit current when using
-> the unit as a battery charger (ie 25 Watt bulb for
-> 2 Amperes, 35 Watt for 3 Amps, etc.).

->  Also, I'd measure the unloaded output voltage. I'm
-> afraid that it will be too high to be safe as a
-> power supply. Many parts have a maximum rating of
-> 15 or 16 VDC. Running them at the maximum is very
-> dangerous.

 Padding down the circuit with a load resistor of the proper wattage
across the output will allow some battery chargers to safely be used as
a DC power supply. Of course it does reduce the current capabilities
avaialble. 
 In fact in a recent Ham magazine they had a modification that allowed
one to use a Computer Power Supply as a 12 Volt source. The Secret is to
load the +5 volt line to about 2 or 3 amps. 
Two reasons. Computer power supplies are "Switching Power Supplies(Use a
multivibrator type of circuitry) and require loading to stabilize. And
the +5v volt supply in the master regulator. IF you load the +5 as
stated the 12 Volt output will be stable. 
Even a 250 Watt Computer power supply can make a very nice 12 volt
10 Amp bench power supply. 

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