I'm experiencing a weird issue where my Blazer is having a difficult time starting as if the battery were dead. I recently did a full exterior LED upgrade and the battery was near dead every time starting it after it had been driven for a good amount of time. Could the LED lights be leeching power while off? I still need to troubleshoot which ones, of not all.

 

I wouldn't think that switching to LEDs would make any difference. It just might be a coincidence with your battery not performing well with the cold weather upon us (depending on where you live) or that the alternator is not working correctly so that it doesn't charge. When you say you drove it "a good amount of time" how long are you driving it and at what speed? Driving in stop and go traffic might not be enough to recharge the battery if the truck wasn't driven much before you put the LED lights in. I've seen this when I've had my truck in my garage for a couple weeks with incidental opening and closing the doors and ignition being turned on and off etc. The battery might only need one good recharge.

 

So turns out this was all coincidental. The battery just happened to burn out its cells while I was installing LEDs. Didn't show problems while test driving and installing the night of, but then sitting in the garage all weekend and then starting it to go to work Monday morning was when it would start right. Just barely was able to start it all Monday on the weak battery thinking it just needs to be driven (my commutes are 45 minutes). But then Tuesday the battery was dead dead. Got it replaced an dall is working fine.