I got a 20 inch light bar that came with a wiring harness.  The harness has a negative or ground terminal, and on the positive side there is an inline fuse, a relay, a toggle switch with a light, and finally connectors to plug up to two different lights.   I tried connecting the positive and negative wires directly to the battery and it works but the problems is that with that connection if I forget to turn off my led light bar, it would drain the battery.  How can I wire the light to get power only when the ignition is on?   Where would be a good point on the machine to get the power from?  On the front of the ATV near the relay box I found a plug that it is use to have daytime running lights if plugged, or been able to turn them with the handlebar switch if it is unplugged.  It is a pretty thin wire  but it does work only when the ignition is turned on.  (Please refer to the attached pictures to see the plug).  Can i hook up the positive terminal of the harness to such a small wire? 

[2015 Z Force 800 53/Trail EPS]

You can try it but if the LED light bar draws more amps then what that used to supply, then you will have fuse problems or other issues like overloaded light switch..ect. If it were me I would use that wire...or better as you have a switch on the new harness...the accessory positive supply as a relay trigger and continue using the battery as a line source. Relays are cheap and easy to install. Here's a wiring diagram for a positive trigger.


   

NMKawierider thank you very much.     Just to make sure I got it right; use a relay to power the LED bar, and use a positive ignition key line to the relay just to power the relay?        So my harness is missing a separate dedicated positive trigger signal light correct?   

[2015 Z Force 800 53/Trail EPS]

NMKawierider thank you very much.     Just to make sure I got it right; use a relay to power the LED bar, and use a positive ignition key line to the relay just to power the relay?        So my harness is missing a separate dedicated positive trigger signal light correct?   

Yes, the keyed power will only be used to energize the relay(#86),then straight to ground #85 for the coil ground. Then you will still connect the positive of the harness to the battery but just after the fuse, you will cut the positive wire and install the relay, #30 in and #87 out to the lights. To be clear.. you will have the fuse between the battery and the relay. On a side note, if by chance the light bar pulls less then say..4 amps, and most at and under 24"s do, you can just connect it to the light system wire without all this other stuff and just use the switch. My 24" on my Z pulls 4.6 amps and my 7" on the back pulls about 2. I have them on a three-way rocker just hooked to the accessory plug power supply which is keyed power and fused with a 10 amp fuse. Works fine.

Perfect thanks for the explanation, I do have a clear idea on how to use the really and modify the harness to work.

ALLEGEDLY my LED bar is 126 Watts..... according to the description from Amazon lol. For the price that is imposible and its gotta be more like 50W or so.
https://www.amazon.com/gp/product/B06XQGQTXQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I doubt is that powerful but if it was then it would allegedly pull 10.5Amp which should blow the 10Amp fuse on the included harness !

To Connect it directly to the light system just splice the wire that goes to the headlights?   Is there and actual accessory plug power supply on the ATV the I'm not finding?

Confirmed, the bar pull a little less than 4Amp.

[2015 Z Force 800 53/Trail EPS]

For LED light bars of you convert the watts to amps then divide by 2, you will get within 1-1.5 amps of the actual draw. So that one converts to 10.5 amps divided by 2 is 5.25. Yeah..probably 4-4.25. Not sure of what that system on the machine was designed to draw. Might be safer to use the relay anyway..or use the acc plug wire for power.