I have three of the MXJO IMR 18650's since December and have had no issues. They take at least 5 hr's to charge a single and about 7 or 8 hr's for charging two at the same time. The charge is a trust fire TR 001 which I will eventually upgrade to a Nitcore. I believe a slow charge is better for longer overall battery life, there is a very good battery website, called I believe Battery University. Check it out it has a wealth of information.