BatteryBench: A Protocol for Testing Portable Battery Chargers and Electronic Devices for Backpacking

[Rex Sanders]

Companion forum thread to: BatteryBench: A Protocol for Testing Portable Battery Chargers and Electronic Devices for Backpacking

Rex Sanders runs through an extensive protocol for testing portable battery chargers and electronic devices.

[Marcus]

Great start Rex. I’m be interested to see how the Nitecore 10k bank performs too. I could probably send you one for a couple weeks to test if you want. PM me if so.

Another point I’ve noticed – I have a 2 or 3 year old S10+ and also a brand new S10E work phone. I realize the E has a smaller battery than the S and am taking that into account into my remarks. It seems to me (based on observation only, no testing behind this) that as a Li battery ages, it both looses capacity but also becomes harder to charge. The brand new phone (and my S10+ when it was new to ~1 year old) seem to take a charge easier and require less energy from the battery bank. Is there any scientific basis to that or is it just in my head? If there is a basis, one more factor to consider is how many cycles your receiving battery has on it. I guess your watt meter wouldnt really test this, it would just have to be something the user keeps in the back of their mind.

[Rex Sanders]

Marcus,

Nitecore NB10000 test results coming to an online publication near you soon(ish).

The chemistry of rechargeable Li-ion batteries is pretty complicated. From my limited understanding, every recharge gradually makes it harder for ions (and electrons) to move back and forth between anode (-) and cathode (+). Don’t know if that also slows down recharging.

Also, your smartphone charge controller might be working extra hard to extend battery lifespan for the aging battery, at the expense of time and wasted energy. That waste wouldn’t even register on an in-town utility bill, but might make a big difference recharging from a portable battery charger in the backcountry. Would be difficult to test in a reasonable timespan.

— Rex

“A Watt-hour here, a Watt-hour there, and pretty soon you’re talking real energy.”

Not said by Senator Everett M. Dirksen.

[PaulW]

What a well-written and useful article this is Rex. I’m on my second reading. Having spent many years working in testing labs, I can appreciate the hard work you put into this. Thank you!

[John Brew]

Rex, That was a mighty useful article. I decided to order my own FN48 meter and USB load so that I can test my devices. I have a couple of friends who will also want to test their devices.

[Drew Smith]

Hey Rex, great article, which inspired me to order these gadgets in my never-ending quest to optimize absolutely everything in my pack. Plus waste time.

When I clicked on the link for the USB meter, the model you referred to is no longer available. However, a seemingly equivalent model  “SE” is available on Amazon. This one does save mAh values and so is perhaps more convenient for measuring discharge capacities.

[Jerry Adams]

My USB meter doesn’t calculate watt hours.  I’m tempted to buy one.

This is so much funner than working where they tell you how to do something in a way that can’t possibly work, and then complain that it’s not working and you have a bad attitude : )

[Rex Sanders]

Here’s the exact link I used to purchase the USB meter. “Only 17 left in stock – order soon.”

And the load tester. “Only 13 left in stock …” Lead photo shows two units; you only get one.

Sometimes strange things happen to Amazon links on BPL.

And after too many months working on test development and testing, I kinda sorta miss walking down to the basement to run tests. But I’m getting over it :-)

— Rex

[Eugene Hollingsworth]

Good article. Just yesterday I went back to check my USB cables using a similar power meter to see which was delivering more mA’s from my Anker brick to my iPhone. Turns out it’s the Anker cables at 1500 mA, where the the other cables are delivering 900 mA. That would be quite a bit of energy wasted in the cable resistance I suppose.  I then ordered a new 3 ft Anker cable, so I don’t carry the 6 ft.

[Rex Sanders]

USB cable testing is on my radar, because a few others found big differences too. Almost a non-issue for recharging from wall chargers, so cables are rarely tested for energy loss.

Until then: short Anker cables seem to be very good.

— Rex

PS – The load tester I used has vanished from the market, and the Amazon link above points to something else.  Given my bad experience with a different make & model, I won’t suggest anything else without personal testing.

[Jerry Adams]

I have 6 inch USB cables – a little lighter weight and less space.  A USB C for my phone.  Mini for some other devices.

I got some that have no cable – just a connector to plug into battery on one side, and to plug into device on the other side – essentially no cable.  But it seemed like that might break something, weird torque on the connectors.  Better to have a short cable as strain relief.  They weigh less though.

[Kin C]

Thank you for this.

I recommend the sensorpush HTP.xw for your temperature readings. A little bit pricey but the interface and use is excellent.

I’d also be interested in the round trip efficiency of battery packs, say for the case of a solar panel. Along that same vein, the ability to maintain charging despite brown outs or unstable power is also interesting to me. Also I’m curious about the difference between li-poly and regular li-ion cells in terms of cycles or output. Obviously the li-poly is much higher density.

As further interest to durability I’d be curious what the cell cut off voltages are (low/high). You can charge to 4.2V but that generally hurts cells so some manufactures limit to 4.17 or lower for longevity while others might use cheap cells with low cap but spice it up to 4.21 for some extra juice at the expensive of lifecycles.

also I think thermal imaging is interesting because it shows off inefficient circuits, wires, or otherwise poor designs that may not be obvious.

lots of angles this could be approached from but I think this is a great start!

 

edit:

I think this guy does excellent work in testing chargers and I find the graphs and the way he looks at cut off voltages interesting

https://lygte-info.dk/info/indexBatteriesAndChargers%20UK.html

[YoPrawn]

Where would one suspect the resistance is coming from in USB cables? Is it the thinness of the wire? Or is it something to do with the connection itself? I’m using generic 6 inch USB for my Anker, so I would imagine even with thinner gauge wire, the distance wouldn’t be long enough to matter much would it?

I know DC energy drops significantly with distance from wire resistance, so would one only see those issues in longer cords?

And sorry for going a little off topic, but one interesting approach DJI (drone maker) has come up with is the ability to stack their batteries into a 2-in-1 unit that both charges the drone batteries as well as reversing the flow and able to charge other devices from the drone batteries. For people who do drone photography backpacking, they can then put all their energy weight into the drone batteries for the drone’s needs, and then anything else that needs topping off like phone and headlamp can be taken from them as needed. This is more weight efficient for someone doing a lot of drone work, as then the energy is already converted into the proper voltage for the drones and available directly for their operation. There is no energy loss associated with converting power from a power bank to the drone batteries, especially if there is a voltage delta between the two (3.6 vs 7.2 volts). I have a similar system I can use with my headlamp, but since the headlamp uses so little energy, it doesn’t save much weight as the energy from the headlamp cells is then no different than using a power bank. Would probably work better if I needed to use the headlamp at max output for long hours every night.

[Rex Sanders]

Based on what I’ve read so far, USB cable resistance (energy loss) can come from skinny/skimpy/low-quality wires hidden inside the cable; low-quality USB connectors; and overall cable length – shorter is always better for the same design.

That’s why I recommend shorter, thicker cables from reputable brands like Anker until I can do more testing. Cable energy loss testing is surprisingly rare; most reviewers are happy if it works with an AC charger, when you wouldn’t even notice the difference under most conditions. “Hmmm, wonder why the cable is smoking?” Crazy-high new Power Delivery (PD) wattages (240 W over USB-C!) could change that for a small subset of cables and use cases.

Soon you might be able to cook more easily with electricity while backpacking :-) Much safer in high-fire-danger areas, like almost everywhere in a few years.

— Rex

[Arthur B]

Very interesting article.  And a well-structured set of tests.  And I also enjoyed hearing you discuss this material on the recent podcast.

I have an iPhone that I charge overnight on backpack outings, so your iPhone advice was of specific interest.  ‘So after an iPhone is fully recharged, you should unplug it to conserve PBC energy.’  I like to use my iPhone as a wakeup alarm, so I leave it running overnight.  I was unsure if I would see any benefit by charging, then unplugging the phone.

As you noted, even if turned off the iPhone will turn back on when connected to the PBC.  Do you have any sense of whether or not the ‘wastage’ is due to the iPhone overnight standby power consumption?  I would guess that the iPhone derives all of its operating from the PBC, when plugged into the PBC.  I would expect the somewhat higher voltage of the PCB to back bias the iPhone battery so it would not act as an energy source.

[Rex Sanders]

I was unsure if I would see any benefit by charging, then unplugging the phone.

The short answer is I don’t know. Testing with a USB meter between a battery pack or AC charger, and an iPhone that was fully charged and turned on but sleeping, I saw unexplained jumps and drops in power consumption on the time scale of multiple seconds, even with Airplane mode turned on.

That’s what convinced me to make double sure the iPhone was completely turned off during the plugged-in overnight test – which still consumed a bunch of energy. I’d like to dig into this more, but it’s joined roughly 100 other tests on my to-do list.

Do you have any sense of whether or not the ‘wastage’ is due to the iPhone overnight standby power consumption?

My hunch is the iPhone conserves its internal battery by drawing power from the Lightning port instead. AFAIK there’s no way to turn that feature off except unplugging the PBC. The designers of the iPhone battery management system might have (correctly) assumed that 99% of recharges would be from relatively infinite energy sources like AC chargers or car chargers, whether through Lightning ports or wireless charging.

In an energy-consumption sense, whether a running iPhone uses PBC energy all night tonight, or first thing tomorrow night to recharge its internal battery might make almost no difference. You might want to start the day with a fully-charged iPhone for many reasons.

Using a low-power-consumption device as an alarm, like a watch, might be a good idea. My watch isn’t loud enough when my head is buried in down, but I generally don’t want an alarm while backpacking.

Our pocket-computers are wondrous inventions, but don’t precisely fit every possible use case – like backpackers recharging from PBCs where each watt-hour counts.

— Rex

[Rex Sanders]

Speaking of wireless charging … don’t while backpacking, unless you have no choice. Wireless charging almost always wastes more energy than wired.

Also don’t be tempted by PBCs with wireless charging built-in, thinking you’ll save a handful of grams by dropping a short cable. Adding wireless charging to a battery bank increases its weight more than that.

Haven’t done any testing yet – see my to-do list expanding near light speed :-(

— Rex

[Arthur B]

Rex, thanks for the quick reply.  I would agree that for optimal power conservation, charge the phone then unplug the PBC and turn off the phone.

[Jerry Adams]

Samsung Galaxy S23 has some settings to preserve battery lifetime to address problems that Rex mentioned.

You go to “battery”, then “more battery settings”, then you can turn off fast charging and tell it to charge only to 85%.  This should make the battery last longer.

If one was going on a trip where you might run out of battery in a survival situation, make sure and charge to 100%.

[Jeff McWilliams]

In order for a USB Type-C cable to be spec compliant, it must have Vbus end-to-end resistance of no more than 0.166Ω, and Gnd end-to-end resistance of no more than 0.0833Ω.

According to https://medium.com/@leung.benson/what-does-it-mean-when-a-usb-c-cable-is-rated-at-3a-52b4fd66385e

 

[Jerry Adams]

characterizing my s23, may as well post it, may be useful

running just gaia without taking a track I use 1% of my battery per hour.  Gaia taking a track – 6%.  Gaia taking track and listening to podcast on bluetooth – 7%.

It takes about 10WH out of my USB battery to charge the s23 50% which is enough for a day taking a track and listening to podcast.  They spec the s23 battery at 5,000 mWH.  At 3.6 Volts, that would be 18 WH.  50% of that would be 9WH which is close to my measured 10WH which is approximate and includes some inefficiency in charging it.

My 13,000 Anker USB battery weighs 8.8 ounces.  It delivers 18 WH with 4 LEDs lit, 9 WH – 3 LEDs, 8 – 2, 5 – 1, and 1 WH with the 1 LED blinking.  41 WH total.  That’s enough for 4 days.  Plus, if I start with a fully charged phone I’ll get another day.

The USB battery is rated at 13,000 mWH.  The battery is 3.6 Volts.  Theoretically, it should deliver 46.8 WH.  There’s some inefficiency, and I’ve used this for several years, so that’s pretty close to the 41WH I measured.

If I want to do more than 5 days, quit taking a gaia track.

There’s probably at least one arithmetic error.

Or, it would have been easier to just notice I drained my USB battery on my last trip of 5 days – the last day I quit taking gaia track and listening to podcast.

[Bruce Tolley]

Anybody know where Rex went. He has not posted lately.

[Jerry Adams]

one more piece of data

the 13,000 mAh Anker is okay for 4 days of taking a track with Gaia and listening to podcast but more than that not enough

one solution is to not take a track with Gaia when the Anker starts getting low, but I like taking a track because I like seeing the distance traveled

on my last trip I tried a better solution.  Put the battery in power saver mode, which will put apps to sleep when the screen goes off.  I won’t be able to listen to podcast.  For gaia, if I take a track it will only takes points when the screen is on, but I can work with that:

I turn the screen on momentarily whenever I want to take a track point, like at every switchback or when the trail goes in a different direction.  Or just ignore this and the actual distance traveled will be a little more than what gaia says.

that worked fine on my last trip

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