Simple Gear Tests and USB Recharging

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Home Forums Campfire Editor’s Roundtable Simple Gear Tests and USB Recharging

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    Rex Sanders
    BPL Member


    Companion forum thread to: Simple Gear Tests and USB Recharging

    In his new column, Simple Gear Tests, Backpacking Light author Rex Sanders provides suggestions for at-home gear tests you can do with minimal time and expense. First up – a plan for verifying the capacity of your USB-rechargeable devices.

    Steve M
    BPL Member


    Locale: Eastern Washington

    Nice work…thanks Rex.

    James Taylor
    BPL Member


    Locale: Indy

    During preparation for an unsupported FKT attempt, I tested 5 different Chinese power banks from Amazon to see if their advertised capacity matched their actual capacity, using this same method. 4 of the 5, advertised as 26,800 mAh, were actually 20,000 mAh. The only one that advertised capacity honestly was a $90 battery. Most $20-$30 batteries falsely advertise higher than their true capacity because there is no accountability for these companies on Amazon.

    Jerry Adams
    BPL Member


    Locale: Oregon and Washington

    good testing, thanks, interesting results

    Charging slows down as the device nears 100% charged.  For example, maybe it takes 1 hour to charge to 80% and another hour to charge the rest of the way to 100%.

    I wonder if efficiency drops as you near 100%.

    For example, if you just charge to 80%, could you extend the number of days you could do with the same USB power bank?

    BPL Member


    Locale: NoCO

    Nice review, Rex.

    Just a detail note on both Klein meters, from the manufacturer:

    “This meter will NOT display current below 50 milliamperes, even if it is allowing this to pass through. NOTE: The display will show zero current.”

    Rex Sanders
    BPL Member


    James: (Clutches his chest) You mean some gear makers don’t tell the truth? Seriously, this is why I’m working on Simple Gear Tests so more backpackers can find out for themselves. Can’t test and compare a gazillion cheap, gone-tomorrow whatevers on Amazon and other wild-west marketplaces.

    Jerry: I’ve wondered about efficiency dropping, too. But from what I’ve observed during this testing and what I’ve read elsewhere, smart devices like iPhones in effect “lift off the gas pedal” and pull fewer watts over 80% charge, to extend internal battery life. They also start slow near 0% and ramp up at about 20%. I don’t think this has a big impact on efficiency. Might be worth testing.

    NoCO-Jim: If a device is consuming 49 millamps at roughly 5 volts (but showing 0 mA on the Klein), that’s about 1/4 watt. My dad used to say: “Don’t sweat the small stuff.” Many years later I added: “… unless it adds up to make a real difference.” I plan to test overnight recharging for several devices and see if it does.

    — Rex

    Eric Blumensaadt
    BPL Member


    Locale: Mojave Desert

    Thanks for this review. Very helpful, especially the observation that wire connectors take up some amperage as well as heating a battery via charging.

    I have two chargers, a smaller one rated 4,00 MaH and a larger smart phone-sized one at 10,000 MaH.

    Both can charge my Phone 10C from 20% to 80% in less than an hour.

    Roger Caffin
    BPL Member


    Locale: Wollemi & Kosciusko NPs, Europe

    Hi Eric

    Pedantic: I think you meant 4,000 mAH and 10,000 mAH?
    A capital M means Mega, which is a bit different.

    The wire cables cause some voltage drop.


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