Hi Dave
Actually there is not much different between Nitecore D4 and I4 , The only different is that D4 with a LCD screen , the charge speed are the same, but if you think the nitecore cost long time to charge 18650 battery, you can choose the Xtar ,AWT Battery charger, which with LCD screen and also it can option 0.25A,1A,1.5A when charging your battery. so it may be more faster when charging .