(17) Purple Efest Batteries not as Advertised
Dampfakkus is an independent testing facility in Germany which first exposed that Efest is using cells from other manufacturers, rebranding them, and then advertising over-rated specifications as a marketing ploy for better sales of their batteries.
The purple Efest 2500mah 35 amp battery:
The purple Efest 3100mah 20 amp battery:
The purple Efest 2100mah 30 amp battery:
Unwrapping this Efest reveals a Sony VTC4 cell underneath
[* Excuse the odd grammar in the above quotes. These were taken from Google translations from German or French converted to English.]
Efest does not "manufacture" their own cells, but rewrap original cells by other manufacturers as their own brand. The cells that Efest are re-branding are good quality cells for the most part, but the deception Efest and their distributors use to market their batteries is what is dangerous.
People who are buying these batteries for sub-ohm use and expecting them to perform at the advertised spec are unknowingly using a battery with inferior specifications for that use, which could be dangerous by using a battery above its specification limits. The amp ratings that Efest is advertising are dubious and deceptive. Most other manufacturers use the "continuous discharge rate", an accepted industry standard.
Continuous Discharge Ratings vs Pulse (Burst) Discharge Ratings
The "continuous discharge rating" in amps is the standard specification for amp limits within the battery industry. It is a determination made by the manufacturer and represents the amp limit a battery can be safely used before it will fail.
The "pulse or burst" discharge rating is not a specification standard within the battery industry. Every manufacturer or vendor seems to have their own definition of what the pulse rating is.
A pulse discharge rating is any use above the continuous discharge rating. It is never safe and not within the intended operating parameters of the battery. You should not operate your device above the continuous rating if you can help it. The pulse rating is a condition in which the battery is on basically a buildup to failure. It is exceeding the sustainable and intended discharge rate of the battery. It is inappropriate for a consumer device to operate in the pulse range of its battery.
Which would be why we shouldn't rely on any pulse rating. Any failure, mechanical or electronic, that fires the mod will operate in the 'continuous' mode. If your setup relies on a pulse rating, it's instantly over spec.
If your amp draw is safely in the continuous discharge range, your coil could act almost like a fuse and burn out before the battery is stressed. If you are already running the battery at the edge of it's limits (pulse), there is no margin of safety.
I am of the mindset that you should leave a margin of safety when deciding what resistance coil to use. We probably place too much faith into cheap ohm readers in being precise and accurate. Also, a RDA's post screw unknowingly coming loose can greatly change the coil's resistance.
Everyone is free to set their own parameters, and I can only say what mine are.
I try to never exceed 50% of the CDR (continuous discharge rating) of a fully charged battery (4.2v). So with a 20A batteries, that would be 10A. The above Ohm's Law Calculator tells me that a .4 ohm build is as low as I would want to use.
The reason that I place a 50% limit is because as a battery ages the mAh of the battery degrades, as the mAh degrades so does the batteries c rating (amp limit). So down the road, your 20A battery may only be a 10A battery.
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