Check out this hack. I was inspired by some videos that I saw online. I wanted a more elegant solution. This hack allows you to use the existing 12vDC input that many slimpars already have. I connected an external 12VDC lithium ion battery pack to the slimpar, which makes this an elegant and inexpensive way to make your uplights battery powered. I have ran these for over 12 hours, but I calculate that you can run up to 30 hours on a single 6000mah battery pack.
The bulk of the work is creating your own connector. I used a 4 Pin CB Ham Radio Microphone Female Plug to connect the battery to the 12VDC input on the slimpar.
The wire I am using is a CCTV security camera 12v DC 2.1mm Power Pigtail. I would just go ahead and buy a small pack of male and female ones. You can get these online or locally at Microcenter or Frys. Make sure you wrap the soldered connections in electrical tape, since the cover that goes over the connector is conductive.You can also use heat shrink wrap.
Wiring everything up
Check and double check the positive and negative is wired correctly before connecting anything. I strongly suggest investing in a digital multimeter and checking that you have the correct polarity.
If you look closely on the back of the battery pack , you will notice that the positive(+) is on the inner connector and the negative(-) is on the outer connector. (This is very important to get right)As you can see, I have the red wire(+) connected to pin1 and the black wire(-) connected to pin4.