Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Rather than poke things into the undamagedcharge port of our battery, I built a quick-and-dirty mechanical duplicate:
Bafang battery – charge port simulator
The “center pin” is a snippet of what’s almost certainly 5/64 inch brass tube measuring Close Enough™ to 2.1 mm, with a few millimeters of 3/32 inch tube soldered on the end to simulate the nugget.
The aluminum rod has a 5.5 mm hole matching the coaxial jack’s diameter and depth, with a smaller through hole for the “pin” and a dab of Loctite bushing adhesive.
Then I turned the end of a 3/8 inch acetal rod down to a 5.5 mm bushing that completely fills the jack:
Bafang battery – guide bushing – dummy jack
It has a 3 mm hole down the middle to aim homebrew shell drills directly at the pin, while preventing a short to the side contact.
The first test looked encouraging:
Bafang battery – shell drill – test results
The nugget in the damaged jack is definitely larger than my soldered brass tube, but this was in the nature of exploratory tinkering while mulling the problem.
Short-circuiting the Bafang battery’s charge port may have done anything from completely destroying the battery management circuit to just welding a brass nugget onto the port’s center pin. The main output to the bike motor remained functional, so my friend used it on rides over the next few days to reduce the charge level.
Meanwhile, I peeked inside the undamaged battery on Mary’s bike:
Bafang battery interior – overview
The battery pack is neatly shrink-wrapped and firmly glued into the plastic shell, with the battery management PCB on the other side of the battery. Some gentle prying suggests it will be difficult to disengage the adhesive, so getting the pack out will likely require cutting the blue wrap, extricating the cells as an unbound set, then cutting the blue wrap to release the wires.
A closer look at the nose of the battery:
Bafang battery interior – front
The large red wire entering on the left comes from the motor connector, loops around the nose of the battery, and probably connects to the battery’s most positive terminal or, perhaps, to the corresponding BMS terminal.
The medium black wire from the side contact of the coaxial jack (atop the pair of red wires) burrows under the battery and likely connects to the most negative battery terminal. This is the charger plug’s outer terminal.
The small red wire from the center contact of the coaxial jack (between the medium black and red wires) goes to the charge indicator PCB in the nose of the battery. This is basically a push-to-test voltmeter with four LEDs indicating the charge state from about 40 V through 54 V. The small black wire from that PCB burrows under the battery on its way to the BMS.
The medium red wire from the center contact goes to the BMS.
There is no way to determine how much damage the short might have done, although the silicone-insulated wires should have survived momentary heating, unlike cheap PVC insulation that slags down at the slightest provocation.
Removing and replacing the coaxial jack requires Cutting Three Wires then rejoining them, a process fraught with peril. You must already have a profound respect for high voltages, high currents, and high power wiring; this is no place for on-the-job learning and definitely not where you can move fast and break things.
With this in mind, the only hope is to remove the nugget and see if the battery charges properly.
The trick will be to do this without any possibility of shorting a metallic tool between the center pin and the side contact.
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
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.
While looking for something else, Mary came across a walker in the attic and mentioned that, if she ever had to use it, the shortest position of the adjustable legs would put the hand grips too high for comfort. Maybe they
Well, I can fix that:
Walker shortening – hole indexing
The holes are an inch apart, so I clamped the V blocks parallel to the X axis on the drill press, zeroed the X axis knob, slid the leg to get the drill bit into the last hole, clamp in place, crank the table an inch, then use a step drill to start the hole:
Walker shortening – hole drilling
The holes are just slightly larger than the 1/4 inch step on the drill, so the twist drill cuts them to size.
A tubing cutter sliced an inch off all four legs and all four frame tubes:
Walker shortening – latch relocation
The white plastic fitting in the frame tube prevents the legs from rattling, but I had to drill another hole to move the latch button, too.
Yeah, it’s just seven pairs of holes drilled with a 5/8 inch Forstner bit in a scrap 2×4, which was then introduced to Mr Belt Sander to peel off the dust of ages.
There’s a spare set of holes in front because I’m absolutely certain that, without them, another pair of pliers would suddenly pop into existence on the bench.
Those antibodies will gradually disappear during the next few months and, unfortunately, a past Lyme infection does not prevent future infections.
The tick also injected Babesia parasites which do not respond to antibiotic treatment:
Babesia test – 2021-11-10
The “titer” refers to the dilution required to produce a negative test result, with the 1:64 reference titer representing six successive 50% dilutions. My blood required ten 50% dilutions to produce a negative result for the IgG antibodies and (presumably) six 50% dilutions from a 20% base for the IgM antibodies.
As I understand the situation, IgM antibodies appear promptly upon infection and IgG antibodies follow along later, so my reaction to the Babesia infestation was ramping up after two weeks.
In the Bad Old Days™, quinine was the go-to treatment for parasitic infections, but it has a host of horrific side effects at the dosage required for traction against actual diseases; tonic water ain’t gonna get you where you need to go.
The new hotness is atovaquone, arriving as 100 ml of a yellow liquid with the consistency of latex paint, (allegedly) the taste of “tutti fruitti“, and a price (modulo your drug plan) making inkjet printer ink look downright affordable. You might expect to get a 5 ml measuring spoon along the the bottle, but suffice it to say it’s an exceedingly good thing I’m well stocked for printer cartridge refilling.
All of the diseases and drugs list “fatigue” / “drowsiness” / “malaise” as symptoms / side effects and I’m here to tell you knocking off a couple of hours in the recliner during the day does nothing at all to disturb another nine hours in the sack overnight.
A few weeks of low productivity in the Basement Shop™ will definitely count as a successful outcome.
The Smell of Molten Projects in the Morning 