Efficient Battery Practices

1. mAh is the best metric I’m aware of.
2. The faster you charge, the more voltage is lost in resistance and diffusion.  While the newer batteries are much better at charging and discharging quickly without losing as much efficiency, all batteries are more efficient if charged / discharged more slowly.
3. Cold batteries have more losses when charging / discharging (diffusion of the ions in solution occurs more slowly).  The charge doesn’t go away if you’re not drawing current.  And it’s much less of an effect at low current draws.  And many lithium battery chemistries tolerate much lower temperatures than alkaline or NiCad batteries did.

Battery brick manufacturers lie about capacity.  A lot.  You don’t get 10,000 mAh out of a “10,000-mAh” battery.  The name-brand companies lie less than the cheaper vendors on eBay, but go by trusted reviews and your own testing of how long / how many recharges you can get from a battery.

I use one of these to 1) check different wall and car chargers, 2) compare different cables, 3) measure the charging rates of usb-headlamps, UV water treatment, etc, 4) measure and integrate the input and output of battery banks ($1.48 US including shipping, alternates between voltage and amp readings):

https://www.ebay.com/itm/USB-Charger-Doctor-Current-Voltage-Charging-Detector-battery-Voltmeter-Ammeter/173445783351?hash=item28622c9f37:g:aTUAAOSwvylbYqxg

The style below (costs more at $11, but) appears to integrate amps into amp-hours which would be REALLY handy when putting a battery brick through its paces and free you to do other stuff rather than recording amps every 5-10 minutes during multiple recharges.

https://www.amazon.com/Eversame-Multimeter-Voltmeter-Thermometer-Electricity/dp/B071KVBSXG/ref=asc_df_B071KVBSXG/?tag=hyprod-20&linkCode=df0&hvadid=309722091285&hvpos=1o4&hvnetw=g&hvrand=14180224845324476496&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033901&hvtargid=pla-568017420926&psc=1&tag=&ref=&adgrpid=60439548223&hvpone=&hvptwo=&hvadid=309722091285&hvpos=1o4&hvnetw=g&hvrand=14180224845324476496&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033901&hvtargid=pla-568017420926

Edited to add: when I first checked all my car chargers and cables, I found out I hadn’t been imagining that sometimes my phone would charge VERY slowly.  When testing them, I’d switch meter and cable and phone from one charger to another (so the only difference was the charger) and see perhaps 0.92 amps from one charger and 0.18 amps from another.  So I threw away the crappiest chargers and life had been better ever since.

Personal choice of course, but wired earbuds and a solar-charged watch?…just sayin’.

I’ll probably get one of those Garmin watches one day.  I use an Apple Watch every day, except when I’m hiking or swiming.  Then I pull out the trusty timex ironman watch

“The 10,000 mAh rating is of the 3.7 V lithium battery that’s contained inside. “

I’ve heard that before and I don’t doubt that is their rationalization.  Like the 11-amp table, 120-volt Sears saw that is “5 peak horsepower” because it delivers 5 hp for a fraction of a second due to the momentum of the motor and blade.  Or, to claim the starting battery in my car can do 3000 cold-cranking amps because it produces 500 amps (at 2.2 volts ) in the first cell), plus 500 amps at 2.2 volts in the second cell, plus 500 amps. . .

It’s a lie.  And some vendors lie more than others.  So test any battery bank.

Agreed, the Anker “10,000 mAh” is popular.  Look at reviews for how many times it can charge your particular devices.

More so, practice minimizing usage and power consumption by your devices.  What more does one need than a headlamp on a FKT?  Time spent looking at your devices, vlogging, emailing, etc, just wastes time that could be spent hiking or sleeping.

I often see confusion when people use mAh to compare batteries and battery packs, because it measures current and time at an unspecified voltage – not energy, which is what we (mostly) care about.

Milliwatt-hours are real energy units, independent of the current and voltage(s) involved. A 10,000 mAh battery at 3.7 volts is 3.7 x 10,000 = 37,000 milliwatt-hours or 37 watt-hours. Another battery rated for 10,000 mAh at 5 volts (USB standard voltage) holds 50,000 milliwatt-hours or 50 watt-hours, and so on.

The hard part is knowing what voltage the battery pack maker used for computing mAh. Usually they don’t say.

And there are charging and discharging energy losses, which vary by temperature and charging/discharging speed and target device.

And then there is, umm, stretching the truth by battery pack makers, sometimes a lot.

Some device makers – phones, headlamps, etc. – will state the milliwatt-hours stored in the device, which can help.

But as David said, the only way to really know is to buy a meter and test your devices and your battery pack under your anticipated conditions.

To restate David’s advice as some rules of thumb:

– If you want to save time in town, buy battery packs that can be charged as fast as possible from powerful chargers. (Except they won’t charge any faster from standard or crappy chargers.)

– Charge devices like phones and headlamps from your battery pack in warm conditions – not too hot, not too cold

– Charge devices like phones and headlamps from your battery pack slowly, typically standard USB rates of 0.5 to 1 amp and 5 volts.

– With modern lithium batteries, don’t worry about cold temperatures (within reason) for storage or use.

And I’ll add

– Don’t run devices down to 0% – stop around 10% or the last “bar”. Running down to 0% can sometimes cause harm; and many charge indicators give unpleasant surprises as you get close to 0 (“but I had 10% only 5 minutes ago and it’s dead now!”)

– Try not to charge devices past 90% from your battery pack. Charging that last 10% from 90 to 100 takes a lot more energy than from 80 to 90 due to battery inefficiencies. This is kind of a pain because you can’t plug-and-forget.

Hope this helps.

— Rex

18-20 hours a day for 6 days, wow!

hopefully you’ll post here when you do this.  Posting while you’re doing it would be cool but you will probably be too busy

Eli – If you have sorted out all the battery stuff, can you share what the unsupported FKT is for the LT?  How did the first two attempts end – injury (my usual fate) or too much time?  Beyond all else – GOOD LUCK! We’ll be watching and hoping for success.