As I see it, you have a few choices.
-Leave things as they are.
-Talk, recognizing it might change nothing (or it could end the friendship).
-Stop enabling the behavior and let him learn from the natural consequences.
-Some combination of those.
@Reburn made great points in post #38.
Some of it depends on what people find important. I spent years trying to get my wife to keep her cell phone charged, even got her battery packs and they just ended up dead too. It just did not hit her as important. I had talked about safety before, but it came to a head one day and she asked me why I cared about her phone. I asked her what her plan was if I was at work and our 2 year old daughter started choking to death, or our POS neighbor was trying to break in (we don't have a land line). For some reason, after 10 years of marriage it finally stuck and her phone has not died in over a year.
Don't expect him to change because you ask him too. Perhaps don't ever expect him to take care of group gear. But, it is reasonable to expect him to have his own shit straight more often than not. The consequence should not be from you, just let the natural results play out so long as they are not permanently destructive.
For example, tell him you have the only good headlamp, so you are butchering and he is packing out in the dark. Changing his expectations might be rough though.