BlendJet won't charge, is it usually just the 18650s?

[Thomas Martinez]

Saw someone mention that BlendJets was dying on the charger due to the two 18650 cells within them being toast. BlendJets run a pair of 18650 cells, sitting somewhere around 3.7 to 4V when healthy. If one is cracked open and the voltage of the cells are significantly below that range, they are essentially done for that battery and you wont bring them back to life by leaving it on the charger.
In order to replace the cells, the new cells has to be spot welded together to maintain the battery; soldering directly to the 18650 cells can cook the cells. Thus, to replace the cells, one would have to purchase a spot welder, such as a cheap kWeld or an 18650 specific welder.
I cracked open a BlendJet last summer and found the cells to be mostly garbage; they were no-name, flat top cells with both cells reading around 1.2V. I might replace these with Samsung 25R or LG cells instead. The little BMS that is included in BlendJets is fairly forgiving and should not throw a fit at the replacement of the cells with fresh battery.

 

[Breakable Bison]

cracked one open last summer, the cells inside were absolute garbage no-name flat tops, both sitting at like 1.2V.
swapped in a pair of 25Rs and it's been fine for months, the board didnt care at all.

 

[Quaint Quail]

why bother? a new blendjet is like 40 bucks on sale. By the time you buy a spot welder and decent cell youll spent triple then that

 

[We Love Mounta]

wait so does the charge board actually balance the two cells or is it just a dumb series charger? curious because if there's no balancing thats kind of why they die so fastly in the first place

 

[Breakable Bison]

wait so does the charge board actually balance the two cells or is it just a dumb series charger? curious because if there's no balancing thats kind of why they die so fastly in the first place

from what I saw poking around with a meter it's barely a BMS, more like overvoltage cutoff and thats it. No real balancing which is probably why one cell tanks and drags the other down with it.

 

[Planet of the]

Soldering directly to 18650s isnt as sketchy as everyone makes it sound if you know what your doing. Tin the tip super hot, get on and off in under a second, use a good flux. I've built dozens of packs that way without a welder. The guy who preaches against spot welders the most on the forum has never soldered to a cell in his life. If you've never done it before though, get a welder. The learning curve isnt worth setting up a vented battery in your face.