Monthly Science: USB Current Testers vs. NP-BX1 Batteries

Having some interest in my Sony HDR-AS30 helmet camera’s NP-BX1 battery runtime, I’ve been measuring and plotting recharge versus runtime after each ride:

USB Testers - Charge vs Runtime
USB Testers – Charge vs Runtime

The vertical axis is the total charge in mA·h, the horizontal axis is the discharge time = recorded video duration. Because 1 A = 1 coulomb/s, 1 mA·h = 3.6 C.

The data points fall neatly on two lines corresponding to a pair of cheap USB testers:

USB Testers
USB Testers

When you have one tester, you know the USB current. When you have two testers, you’re … uncertain.

The upper tester is completely anonymous, helpfully displaying USB Tester while starting up. The lower one is labeled “Keweisi” to distinguish it from the myriad others on eBay with identical hardware; its display doesn’t provide any identifying information.

The back sides reveal the current sense resistors:

USB Testers - sense resistors
USB Testers – sense resistors

Even the 25 mΩ resistor drops enough voltage that the charger’s blue LED dims appreciably during each current pulse. The 50 mΩ resistor seems somewhat worse in that regard, but eyeballs are notoriously uncalibrated optical sensors.

The upper line (from the anonymous tester) has a slope of 11.8 mA·h/minute of discharge time, the lower (from the Keweisi tester) works out to 8.5 mA·h/minute. There’s no way to reconcile the difference, so at some point I should measure the actual current and compare it with their displays.

Earlier testing suggested the camera uses 2.2 W = 600 mA at 3.7 V. Each minute of runtime consumes 10 mA·h of charge:

10 mA·h = 600 mA × 60 s / (3600 s/hour)

Which is in pretty good agreement with neither of the testers, but at least it’s in the right ballpark. If you boldly average the two slopes, it’s dead on at 10.1 mA·h/min; numerology can produce any answer you need if you try hard enough.

Actually, I’d believe the anonymous meter’s results are closer to the truth, because recharging a lithium battery requires 10% to 20% more energy than the battery delivered to the device, so 11.8 mA·h/min sounds about right.

Memo to Self: Trust, but verify.

Halogen H3 Bulb

Peering into the bulb salvaged from the Nissan fog light suggests the scuff on the lens corresponds to an impact mighty enough to disarrange the filament:

Halogen H3 bulb - 1.5 A - light
Halogen H3 bulb – 1.5 A – light

No surprise, as the car completely shattered the utility pole.

The glow draws 1.5 A from a bench supply at 1 V, just to show the filament isn’t lighting up evenly across those gaps. The bulb runs at 55 W from 12 V and would be, I’m sure, blindingly bright, although the heat concentrated in those few coils suggests it’d burn out fairly quickly.

By LED standards, though, you don’t get much light for your 1.5 W …

An underexposed version highlights the filament, just for pretty:

Halogen H3 bulb - 1.5 A - dark
Halogen H3 bulb – 1.5 A – dark

Cropped to 9:16, it’s now a desktop background.

Pileated Woodpecker vs. Stump

A pileated woodpecker devoted considerable attention to debugging the remains of a stump in our front yard:

Pileated Woodpecker - front yard stump
Pileated Woodpecker – front yard stump

It’s surely a descendant of this one, eleven years ago:

Pileated Woodpecker
Pileated woodpecker

If you’re willing to wait a decade or so, a stump pretty much falls apart on its own, meanwhile providing habitat for critters both great and small.

Update: By popular demand, a slightly pixelated pileated woodpecker:

Pileated Woodpecker - front yard stump - pixelated
Pileated Woodpecker – front yard stump – pixelated

Monthly Image: Moonrise

With some heavy weather on the way:

Moonrise in Red Oaks Mill - 2020-04-08
Moonrise in Red Oaks Mill – 2020-04-08

Bracing the Pixel 3a on the deck railing. Despite the star near the top, it decided to not invoke Astrophotography mode.

This was apparently a Pink Moon and a Supermoon and surely some other adjectives nobody cared about until Webbish media discovered they could generate ad revenue using clickbait headlines concerning a monthly event.

We just enjoy the sights out along the driveway, whatever they may be.

Monthly Science: Praying Mantis Ootheca

We extracted the Praying Mantis oothecae while clearcutting the decorative grasses bracketing the front door. As far as I can tell, they’re still charged up and ready for use.

The masses resemble rigid foam wrapped around grass stems:

Praying Mantis ootheca - stem side
Praying Mantis ootheca – stem side

It’s a mechanical joint, not an adhesive bond, and the dried stems slide freely through the openings:

Praying Mantis ootheca - bottom
Praying Mantis ootheca – bottom

From one side:

Praying Mantis ootheca - right
Praying Mantis ootheca – right

And the other:

Praying Mantis ootheca - left
Praying Mantis ootheca – left

They’re now tied to stems of the bushes along the front of the house, which (I hope) will resemble what the little ones expect to find when they emerge, whenever they do.

Monthly Image: Albino Squirrel

We’re riding home with groceries when a small white shape scampered across a yard and jumped onto a stump:

Albino Squirrel 2020-03-03 - 680 crop
Albino Squirrel 2020-03-03 – 680 crop

If you’ve ever seen a gray squirrel, you’ll recognize the shape, even in this gritty enlargement:

Albino Squirrel 2020-03-03 - 680 - detail crop
Albino Squirrel 2020-03-03 – 680 – detail crop

Wikipedia says this one is likely a leucistic white squirrel, rather than a true albino squirrel. There is, of course, a website. tracking “white squirrel” sightings.

The relevant coordinates, for science:

41°41'39.9"N 73°52'56.6"W
41.694410, -73.882374

Can’t say if this one had black or pink eyes, but it was pure white!

Batmax NP-BX1 Batteries

Having recently lost one of the year-old DOT-01 batteries, a quartet of Batmax NP-BX1 batteries for the Sony HDR-AS30V helmet camera just arrived:

Batmax DOT-01 Wasabi NP-BX1 - 2020-04
Batmax DOT-01 Wasabi NP-BX1 – 2020-04

The orange curve is the last surviving (“least dead”) Wasabi battery from the 2017-08 batch and the dark green curve just above it is another DOT-01 from 2019-02. The problem is not so much their reduced capacity, but their grossly reduced voltage-under-load that triggers a premature camera shutdown.

The Batmax batteries measure better than the craptastic Wasabi batteries, worse than the STK batteries, and should survive the next year of riding. As before, I have zero belief that Amazon would send me a “genuine” Sony NP-BX1 battery, even at six times the nominal price, nor that it would perform six times better.

Batmax is one of many randomly named Amazon Marketplace sellers offering seemingly identical NP-BX1 batteries: Newmowa, Miady, Powerextra, Pickle Power, LP, Enegon, and so forth. Mysteriously, it’s always cheaper to get a handful of batteries and a charger, rather than just the batteries, so I now have a two-socket USB charger:

Batmax NP-BX1 - USB dual charger
Batmax NP-BX1 – USB dual charger

Despite the “5 V 2 A – 10 W” and “4.2 V 0.6 A – 5 W” label on the back, charging a pair of batteries after a ride started at 700 mA from a USB 3.0 port. The charger makes no claims about USB 3 compliance, so I’d expect it to top out around 1 A from a generously specified port.