As more and more rechargable devices offer USB passthrough as part of their feature list, it is tempting to ask oneself, why do I need to carry around a spare battery, especially if I work around a USB all the time?
USB passthrough is a nice feature, and when you are in a pinch, it will save your hind end. However, it does not, and should not replace carrying around a spare.
USB passthrough is considered a parasitic load. Parasitic loads are VERY stressful on a battery. Using USB passthrough on a regular battery will drastically shorten it's lifespan.
"Some portable devices sit in a charge cradle in the on position. The current drawn through the device is called the parasitic load and can distort the charge cycle. Battery manufacturers advise against parasitic load because it induces mini-cycles. The battery is continuously being discharged to 4.20V/cell and then charged by the device. The stress level on the battery is especially high because the cycles occur at the 4.20V/cell threshold.
A portable device must be turned off during charge. This allows the battery to reach the set threshold voltage unhindered, and enables terminating charge on low current. A parasitic load confuses the charger by depressing the battery voltage and preventing the current in the saturation stage to drop low. A battery may be fully charged, but the prevailing conditions prompt a continued charge. This causes undue battery stress and compromises safety."
Charging Lithium-Ion Batteries
Using the USB passthrough once an awhile will by no means destroy your vv3 or MVP 2. However USB passthrough does not substitute the need to have a charged spare available.
USB passthrough is a nice feature, but regular use will cause you to wear out your battery quicker. Your better off in the long run buying several batteries and swaping them out and letting them charge (with the power off) than you are buying simply one and running it on USB passthrough throughout the day.
Once it does get near it's end of life, then I suppose you can retire that battery as a "passthrough only" device....
USB passthrough is a nice feature, and when you are in a pinch, it will save your hind end. However, it does not, and should not replace carrying around a spare.
USB passthrough is considered a parasitic load. Parasitic loads are VERY stressful on a battery. Using USB passthrough on a regular battery will drastically shorten it's lifespan.
"Some portable devices sit in a charge cradle in the on position. The current drawn through the device is called the parasitic load and can distort the charge cycle. Battery manufacturers advise against parasitic load because it induces mini-cycles. The battery is continuously being discharged to 4.20V/cell and then charged by the device. The stress level on the battery is especially high because the cycles occur at the 4.20V/cell threshold.
A portable device must be turned off during charge. This allows the battery to reach the set threshold voltage unhindered, and enables terminating charge on low current. A parasitic load confuses the charger by depressing the battery voltage and preventing the current in the saturation stage to drop low. A battery may be fully charged, but the prevailing conditions prompt a continued charge. This causes undue battery stress and compromises safety."
Charging Lithium-Ion Batteries
Using the USB passthrough once an awhile will by no means destroy your vv3 or MVP 2. However USB passthrough does not substitute the need to have a charged spare available.
USB passthrough is a nice feature, but regular use will cause you to wear out your battery quicker. Your better off in the long run buying several batteries and swaping them out and letting them charge (with the power off) than you are buying simply one and running it on USB passthrough throughout the day.
Once it does get near it's end of life, then I suppose you can retire that battery as a "passthrough only" device....
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