My maratac peanut wont charge fully on a 26000mah ravpower bank. Once current gets low i think something shuts down.
My maratac also failed in a week. So now ive added a xpg3 s5 copper 5000k led with direct drive. 1.2amps and 500 lumens for 5 minutes of fun lol. In hindsight I think aa sized batteries or something with over 30 mins runtime is worth the extra weight after having 20 mins max as standard at only 150 lumens.
If we're talking something that's not rechargeable or doesn't use coin-cells, I think some of the smaller single-AAA models would be a good choice. I have Fenix's single 10180 offering. It was the last keychain light I had on my key-ring before the Nitecore Tube arrived. It worked decently. Though I believe I had the same Battery Bank issue with that one as well.
I just wanted as least bulky a keychain set-up as possible that incorporates a couple of extra accessories besides keys. Also, I just didn't have confidence in that little Fenix light. Can't explain it.