The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: Repairs

If it used to work, it can work again

Bafang Battery Charge Port: Whoopsie
The Bafang mid-drive e-bike kits I installed on Mary’s Tour Easy recumbent and a friend’s Terry Symmetry used the “Ultra-Slim Shark” lithium battery, a rectangular lump with a tapered snout:

Bafang BBS02 – Terry Symmetry full assembly

The battery has a key lock on its left side:

Bafang battery – lock

The lock might deter casual thievery, but really prevents the battery from bouncing out of its mounting plate while riding.

The right side has a charge port closed with a rubber plug:

Bafang battery – charge port – closed

The cover protects a coaxial jack with a 5.5 mm OD and a 2.1 mm center pin:

Bafang battery – charge port

My friend in Raleigh generally removes the battery before hoisting the bike into the back of her car to haul it to a friend’s house for their companionable rides: not lifting an additional seven pounds is a Good Idea™.

A momentary distraction in the middle of that process caused her to insert the brass key into the charging port, rather than the lock. The key put a very short circuit between the coaxial jack’s side contact and the center pin, melting the key tip and welding a brass nugget onto the side of the pin:

Bafang battery – damaged charge port

The charger plug normally sits almost flush to the port’s surface:

Bafang battery – charge plug

The nugget keeps the plug out the damaged port, preventing the plug from making electrical contact:

Bafang battery – damaged port – plug

She owned the problem and immediately bought another battery, which tells you the value she places on riding her e-bike.

Verily it is written: let someone who is without whoopsie cast the first shade.

Any takers? Yeah, the way I see it, someone who says they’ve never done anything quite like that is either not doing anything or not telling the complete truth. For sure, I’ve done plenty of inadvertent damage!

Here’s the problem:
- The damaged battery is the better part of 600 miles away from my shop
- Civilians cannot ship 560 W·hr lithium batteries through any parcel delivery service
- Civilians cannot fly or take the train with such a battery, either
- Driving 1200 miles twice is out of the question for either of us
How would you proceed?

More to come …

For reference:
- USPS – Hazardous Material Info – section 349.222
- UPS – Lithium Battery Pack & Ship – PDF page 9
- FedEx – How to Ship Batteries – PDF page 3
Basically, it is possible to ship lithium batteries up to 100 W·h.
2021-12-13
Dirt Devil Vacuum: Stuck Adapter

My tool adapters for the Dirt Devil stick vacuum cleaner worked fine when inserted into the power unit, but got stuck in the floor brush extension tube:

Dirt Devil Floor Tube – stuck adapter

The adapter rotated freely inside the socket, so its diameter was correct and it wasn’t jammed, but pushing the latch button (at the depression on the right) didn’t release the adapter.

Popping the latch out of the tube let the adapter slide easily out of the socket and exposed the innards:

Dirt Devil Floor Tube – latch internals

The two bosses inside the latch originally captured a nice conical spring:

Dirt Devil Floor Tube – conical latch spring

The tab on the left side of the latch button engages a slot in the OEM brush head and the recessed ring around my adapters:

Dirt Devil Nozzle Bushing – solid model

It turns out the molded tab was slightly too long, so pushing the latch button all the way down didn’t retract the tab out of the bore, so it remained engaged in the adapter’s ring.

The conical spring also didn’t seem to collapse completely flat, so the bosses inside the latch button couldn’t quite bottom out, leaving the tab protruding even further inside the bore. It also required an inordinate amount of force to push the latch all the way down.

While fiddling with all this, I noticed that the OEM floor brush would sometimes hang up on the tab, so the operation wasn’t all that smooth even with the original equipment.

So I trimmed maybe half a millimeter off the tab, just enough to release the adapter with the button fully pressed and without the conical spring, then replaced the conical spring with a tiny spring (from the Big Box o’ Random Springs) trimmed to allow the full range of travel. This not only released the adapter, it also let the OEM floor brush pop out more easily.

A zero-dollar repair, although with considerable annoyance.

2021-12-09
Incandescent Bulb Lifetime: Also Better Than Average

This bulb spent the last seven-plus years of its life lighting the front bathroom:

Dead incandescent bulb – 7 years

The green corrosion around the tip seems strange, given that we don’t use the tub or shower in that bathroom, and I’m pretty sure it wasn’t the cause of the failure.

My stock of incandescent bulbs will eventually run out; I must figure out how to light the deaders in an attractive manner.

2021-11-30
CFL Lifetime: Better Than Average

Although compact fluorescent lamps have fallen out of favor, I’m burning through a box of the things donated by a friend who upgraded to LEDs and figured I could put them to good use. In general, complex electronic doodads (like CFL or even LED lamps) used in hostile situations (like an ordinary downlight fixture) seem to fail too quickly to justify the power savings; searching for “cfl fail” will produce some evidence from around here.

One of the downlights in the Basement Office just killed this specimen:

Dead CFL – detail

Much to my surprise, however, it survived for more than five years:

Dead CFL – over 5 years

The previous CFL bulb in that fixture lasted only two years, so their average lifetime is entirely too short.

A taller bulb does a better job of lighting up that corner, although it started with enough power-on hours to suggest it won’t survive for another five years:

Dead CFL – replacement

The ghostly humps above the overexposed glare are the long CFL tubes reflected inside the Pixel’s camera optics.

I didn’t see much point in nailing a ceiling to too-low floor joists.

2021-11-18
Alpha Geek Clock: Battery Refresh

A pair of D cells can power an obsolete / out of production C-Max CMMR-60 WWVB receiver for about five years and, having the plastic pieces for a blinkie at hand, junking the faded case in favor of a test lashup seemed appropriate:

C-Max CMMR-60 WWVB receiver – AA alkaline test setup

Given the fragility of that ferrite bar, I should conjure a wide D-cell base, a bar holder to cover the ends, and a PCB mount of some sort.

The receiver data pin drives the red LED of an RGB piranha through a 2.2 kΩ SMD resistor, so it’s visible in a dim room. Given that the thing flickers constantly during WWVB’s poor-reception daylight hours, reducing the LED current counts for almost everything.

The antenna has a cap under that heatshrink tubing, which called for a resonance check:

C-Max CMMR-60 WWVB receiver – antenna peaking – driver coil

The blue dingus is an RF sniffer driven three orders of magnitude below its frequency spec:

C-Max CMMR-60 WWVB receiver – antenna peaking – function generator

The antenna response peaks where you’d expect:

C-Max CMMR-60 WWVB receiver – antenna peaking – scope

Given the broad peak and typical tolerances, it’s spot on.

2021-11-15
Alpatronix iPhone XS Max Wireless Charging Case: Battery Capacity

Mostly because I have the technology, here’s a battery rundown test for the (guts of the) Alpatronix iPhone case:

Alpatronix iPhone XS case – battery test setup

Bypassing the entire battery controller doesn’t tell you when it thinks the lights should go out, but does give an indication of the raw battery capacity:

Alpatronix iPhoneXS Charger – 2021-11-06

Multiplying the nominal 3.7 V by the nominal 5 A·hr capacity says it should have a nominal 18.5 W·hr capacity at some unrealistically low discharge rate. Given that I found it at the end of the driveway with no provenance, I didn’t expect much.

To my utter astonishment, it delivered 17 W·hr at 500 mA!

It really ought to be good for something …

2021-11-12
Shopvac QSP Motor Commutator Cleaning

The Greatest Shopvac emitted an intense smell of electrical death while inhaling fuzzballs from the Basement Shop stairs, prompting me to tear it down. For the record, it’s a Genuine Shop·Vac QSP 10 (Quiet Super Power):

Shopvac QSP – label

Removing the handle and upper plate reveals a slab of (presumably) sound-deadening foam over the motor cooling fan. As far as I can tell, the last job this vacuum had before the previous owner discarded it was inhaling drywall dust without a filter:

Shopvac QSP – upper sound baffle

Flipping the motor assembly over and removing the bottom plate revealed a pair of equally solidified foam slabs baffling the main exhaust path:

Shopvac QSP – sound baffle foam

They eventually became Clean Enough™ after protracted rinsing, so maybe the thing now runs as quietly as the name would lead you to believe, if you believed in names.

Disconnecting and extracting the motor revealed the razor-sharp impeller disk. A shop rag prevents lacerations while torquing off the nut holding it to the shaft:

Shopvac QSP – impeller nut

Rust on the washer below the impeller, along with the layer of caked white cement, suggested water accompanied the drywall dust:

Shopvac QSP – impeller washer

Gentle suasion from the Designated Prydriver eventually eased the washer off the shaft and freed the motor:

Shopvac QSP – motor brush layout

It’s an old-school series-wound brushed universal motor. The plastic plate in the middle of the picture has a helical spring pressing the carbon brush against the commutator:

Shopvac QSP – motor brush detail

The rotor turned … reluctantly with the brushes in place and spun freely without them, suggesting the horrible smell of electrical death came from arcing across the gunk accumulated on the commutator:

Shopvac QSP – commutator as found

Many iterations of diligent scrubbing with denatured alcohol on cotton swabs and old t-shirt snippets got rid of the crud, although that commutator will never look all shiny-clean again:

Shopvac QSP – commutator cleaned

At least the brushes aren’t glued to it!

Reassembly is in reverse order, although I took the liberty of splicing a few inches of wire into the switch leads, because I’m not working under factory conditions with all the proper assembly fixtures:

Shopvac QSP – extended wires

The motor passed the smoke test and no longer smells like death, so it’s at least as good as it ever was.

It may run quieter with clean foam baffles, but I still turn off my power ears or don hearing protection when I fire up any shop vacuum.

2021-11-11