2-cell USB lithium power bank comparison.
bigclivedotcom 4:32
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While ordering random stuff on ebay I decided to add two different 2-cell USB power bank cases to the order to see how they differed. One has an LED torch built in, but unlike the "intelligent" units that control the LED with a couple of presses of the control button, this one just has a small switch that powers it directly from the two parallel cells with a 10 ohm resistor in circuit to limit the current.
The small case with the LED flashlight facility is actually TOO small and they have seriously compromised the space for the cells to the point they are a tight fit and push the barely supported positive contact dangerously close to the PCB and USB connectors shell. The only thing that seems to make an attempt to contain the cells is two flimsy support pillars on the lid! The chip used is the common FM6316FE which has upper limit charge cut-off but lacks proper over-discharge control other than turning the boost converter off. A load capable of passing current below about 2.5V will potentially damage the cell if left connected continually. Standby current of the small pack is 18uA.
The bigger pack is a completely different beast. It's styled on the common chunky power banks that have the text "Power bank" embossed into them, and on first sight it appears to use the exact same PCB as the smaller version, but on closer examination it has a more complex PCB (perhaps an older pre-FM6316FE style?). There are three chips on it that have little data on the 'net but seem to be a lithium protection chip, associated dual MOSFET chip and presumably the voltage booster. This does suggest that it may actually switch off at upper charge limit AND lower discharge limit. Standby current is slightly higher at 44uA.
Neither pack will accommodate the extra length of a protected 18650 cell. Hopefully the bigger pack completely negates the need for protection anyway.
Both packs are yellow because I favour bright colours if I'm going to use things like this at work, since the bright colour makes them harder to lose.
The small case with the LED flashlight facility is actually TOO small and they have seriously compromised the space for the cells to the point they are a tight fit and push the barely supported positive contact dangerously close to the PCB and USB connectors shell. The only thing that seems to make an attempt to contain the cells is two flimsy support pillars on the lid! The chip used is the common FM6316FE which has upper limit charge cut-off but lacks proper over-discharge control other than turning the boost converter off. A load capable of passing current below about 2.5V will potentially damage the cell if left connected continually. Standby current of the small pack is 18uA.
The bigger pack is a completely different beast. It's styled on the common chunky power banks that have the text "Power bank" embossed into them, and on first sight it appears to use the exact same PCB as the smaller version, but on closer examination it has a more complex PCB (perhaps an older pre-FM6316FE style?). There are three chips on it that have little data on the 'net but seem to be a lithium protection chip, associated dual MOSFET chip and presumably the voltage booster. This does suggest that it may actually switch off at upper charge limit AND lower discharge limit. Standby current is slightly higher at 44uA.
Neither pack will accommodate the extra length of a protected 18650 cell. Hopefully the bigger pack completely negates the need for protection anyway.
Both packs are yellow because I favour bright colours if I'm going to use things like this at work, since the bright colour makes them harder to lose.
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