I have a MiBoxer C4 that clearly states in the back that it will fit 21700 batteries. However I tried to charge mine today and it doesn’t fit. I have a INR21700-50E Samsung SDI. Does anyone know a charger that fill fit this battery?
I have the MiBoxer C2-4000 and it fits but only with 1-2 mm to spare. I need to push the spring down to it’s limit to insert but it fits my 21700 which measures 71mm.
The Samsung you indicate is supposedly a flat top and specified as 70.8mm.
Clearly one thing or other other is amiss.
omgggg I was looking for a new charger which takes 21700 since I bought a Fireflies E07 yesterday, I was about to take the miboxer C4 but finally I took a Vapcell S4 plus !! it’s more pricey but i’m so glad now 
My Miboxer C4-Upgrade fits 21700 cells ok with a little room to spare. Which version do you have. There are like 4 models of C4 and they all vary. I bought a C8 once and it was tighter than the C4-Upgrade even though it says it fits 21700 cells
Mine looks just like yours with the same battery but i dont have the same space you have. Not even close
Can you measure how long your battery is?
I just looked at Miboxer’s website and they have like 5 different models of C4. I kind of don’t think the issue is the battery. Do you know what model of C4 you have? Taking a rough measurement on my C4-Upgrade, there is about 80mm of space with the spring pulled all the way back.
I also have a previous version of this charger that looks exactly the same as this, but does not work with the longer cells. Miboxer needs to change their model numbers when they make new versions of a charger.
I have a C4Plus, as well as a Xtar VC2S, and both have room to fit a 21700 fine, but the C4Plus can fit protected cells, and the VC2S doesn’t
Since the 21700 was released recently, look at chargers that were released within about the last year or so, since they can handle a higher amp charge also. I use them in my vape gear, and was stuck using on board charging until ~2years ago, when they caught on. HKJ has a fitment list.
Miboxer C4 model are confusing.
Get the C4-Plus. There is only one C4-Plus. I measured the slot estimate @78mm. I guess it can take any 21700 protected cell currently available in the market.