My Nitecore UMS4 USB had inconsistent tests on internal resistance from the start, then the display pooped out on me, went to a basic charger from Night Owl i think…
But im now getting into 21700 batteries and wanting a good, powerful charger that can give me more info, check for capacity and possibly battery health..
Needs to be able to run on 12v D.C. or HP USB..
Im still searching now but thought id ask here as well.
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My charger of choice is the Vapcell S4 Plus.
I asked ChatGPT this question…
Can a Vapcell S4 Plus run on 12v D.C. or HP USB?
Here’s the answer… 
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Vapcell S4 Plus V3.0
I have it about 3 years and im very pleased with it ! (Especially for it’s money !) (And the powerbank function it works perfectly, i test mime 2 times without any problems !)
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