Just a small review and comparison for using these with 18650s The Luc V4 and Nitecore D4 are said to be the top chargers available. Both are good chargers and dependable, but neither are without miner faults. The Luc V4 has a much nicer display then the Nitecore D4. It shows the voltage on all the batteries at once, whereas you have to hit a button to cycle the display on the D4 to select which battery to show info on. I like that the D4 will actually say 'ALL' when all the batteries in it are fully charged. The Luc V4 is compatible with a wider range of batteries then the D4. However, this also causes an issue. The slots are bigger on the Luc V4 so it can accept 26650 batteries. This means that 18650s wont fit snugly in the slots and I have found that it can misread the battery voltage if they are not put in the slots perfectly. Often times I will have 1 battery reading up to a few tenths of a volt higher then the other until I remove and replace them a few times. The negative contacts on the Luc V4 are much easier to slide down to put batteries in the charger. Whereas the stiffer ones on the Nitecore D4 hold the batteries tighter in place. The stiffness of the negatives on the Nitecore can cause issues though, I have had them bend over time (just a millimeter or two) from sliding them down when putting batteries in it, making them not contact the battery negative. It takes 6+ months of daily usage and they are easy to bend forward back into place though. Another minor issue is that with the stiff springs, it is easy for them to 'fling' the battery out of your hand if your not holding it tight enough when pulling them out if you lift the positive out first. Whereas if you pull the negative out first it is easier for the springs to make the negative terminals scrape the side of a battery and possibly damage the wrap. Overall, it is really hard to say which I like better. But my opinion is leaning more towards the Nitecore due to how it holds 18650s in place. It's a bit of a pain having to wiggle the batteries around and slide them down and up to reconnect them in the Luc V4 to get it to show proper voltages. This makes me wonder if it is fully charging the batteries which can be an issue when using married pairs.