I have a Compaq nx9100 with loose power jack which causes intermittent shutdown of the machine.  I did not want to strip the machine and resolder the power jack fitting to motherboard, so made a patch cord with inline socket to fit the DC plug from the AC adapter. The patch cord connects the terminals in the battery compartment (battery charge terminals) to the output of the AC adapter.  This would not work with battery out, but works OK with battery fitted - although battery charge monitoring does not seem to work, so I reset power management to never shutdown.  
 
A 10min workaround for a problem which takes 3-4hrs to fix properly.  But...
 
When I measured voltage across the battery terminals with AC adapter plugged in conventionally (when I could get it to work) I got 14.5V.  My patch cord bodge applies 18.5V DC to the battery.  Anyone know if this is a major problem?  I used the laptop for a couple of hours, it did not seem to run hotter than usual.  

If the patch cord is a separate power supply, than the 18.5v isn't a problem - the voltage will go down under load. "patch" cord is a really odd term, i don't quite know what you mean.
 
I replaced the jack for a compaq presario 2100 a few months ago...it took less than an hour, honestly. just re-solder it.