Unfortunately, many charger manufactures generally cut corners whenever possible in their product designs. Such chargers, even from well known brand name companies, will have issues with charge current regulation and endpoint determination. These things are not visible on the outside—they are apparent only when carefully examining the internal electronics with controlled testing. Further, as there are hundreds of different chargers and batteries (with millions of possible test configurations), it is not really reasonable to expect anyone to have tested all batteries and all chargers. Recommendations are based on best available knowledge to date.
Also, in some cases, manufacturers will put special features into their chargers particular to their batteries. For example, for the Sanyo batteries, the Sanyo charger is the "best"—it has the most smarts tuned particularly for their specific battery brand. For those who want to have a set of "reserve" batteries which are sure to remain charged after sitting in your car for months, the Sanyo Eneloop batteries and chargers are very good in terms of quality, power, and long term longevity.
Anyone looking for the fastest possible alternative charger which is known to be reliable should consider the Energizer 15-minute charger with the Maha Powerex 2700mAh batteries. This is the best combination for people who use the Box at least once every day and who are looking for optimum runtime performance.
Note: Magic-Flight gains absolutely no benefit from our recommendations or advice in this respect—we have absolutely zero association with Energizer corp.
As an alternative configuration for people who use the Box less frequently (not every day) but are still interested in optimum performance, Magic-Flight recommends the Imedion batteries and the Maha MH-C9000 charger—this is the best overall combination for both battery longevity and long vaping sessions. Be advised that this charger is somewhat more complex to use than most chargers and will be more expensive than most to purchase. Magic-Flight staff uses the Maha MH-C9000 internally and find them to be excellent. They are a bit arcane for the average user, but for those who are into the advanced "tech" of rechargeable batteries, it is a great unit.
For nearly everyone else, (the other 90% of Magic-Flight Launch Box users), they recommend the stock batteries and the stock charger, since they are known to have good performance in most circumstances.
Finally, for the record, Magic-Flight does not make the branded chargers that they bundle with the Box. They are provided as a convenience so that people can use the Box without having to worry about such details.