Tour Easy: Bafang 11.6 A·h Range

After a few days of riding, the Bafang 500C display on Mary’s bike gives the battery status:

Bafang 500C display - 48 mi 30 pct
Bafang 500C display – 48 mi 30 pct

The thermometer scale on the right shows 30% remaining battery capacity after 48.3 miles of riding, with the 11.6 A·h battery at 47.3 V.

For our type of riding, each 10% increment of battery charge delivers about 7 miles of range. Although we could probably get 70 miles between charges, recharging the battery at 20 to 30% makes more sense; the bike is in the garage, so why not?

Our typical 10 to 15 mile rides now average 12+ mph, with some level sections ticking along at 18 mph (giving me some serious exercise), which isn’t much by pro rider standards.

Computing the lithium battery charge state by measuring its voltage isn’t particularly accurate, but it’s about as good as you’re going to get.

Goose Parade

Canada Geese seem primed to travel in a straight line, whether in the air, on water, along a rail trail, or even on a sidewalk:

Canada Goose parade - A
Canada Goose parade – A

They proceed around corners in an orderly manner:

Canada Goose parade - B
Canada Goose parade – B

But they completely ignore crosswalk markings:

Canada Goose parade - C
Canada Goose parade – C

We think two goose families joined forces for this outing: four large geese and seven goslings by our count.

The sidewalks sport a rich assortment of goose poop, so the geese obviously enjoy their hikes.

Side Marker Beam Patterns: FAIL

The truck side marker lights I’m thinking of using as daytime running lights have a pentagonal lens, so they should have a pattern with a bright central beam surrounded by five lobes. The one on Mary’s Tour Easy produced an oddly shaped blotch on the garage wall, so I ran the others though a simple test setup:

Side Marker - beam test setup
Side Marker – beam test setup

The lights sit horizontally in a small vise to keep them level and in the same position, although in no particular rotational orientation, and 100 mm from the graph paper. It’s running at 6 v to keep the brightness down enough to avoid blowing out the image. All of the images were exposed based on the central spot, so the surrounding paper gives some idea of the relative brightness: darker paper = brighter LED spot.

The front view of the lights comes from the stereo zoom microscope, with the wires gripped in a Third Hand and rotated to put the (inverted) TOP label where you’d expect it. They’re all roughly at the same position and pretty nearly lined up with the lens axis. The bubble-looking thing behind the central pentagon is the lens on the Piranha LED package, which should be centered but rarely is. You can see the dark orange square of the amber LED chip in some of the pictures.

Without further ado, the nine truck side marker lights that aren’t on her bike:

Side Marker E has a blob that looks like a cataract atop the LED lens, but it might be a mold imperfection.

Obviously, paying a buck a light doesn’t get you much in the way of build quality these days.

Tour Easy: Amber DRL Internal Resistor

Plotting current against voltage for the amber truck side marker lights produces the expected straight-ish line:

Side Marker I vs V plot - with fuse
Side Marker I vs V plot – with fuse

The slope suggests a 330 Ω resistor, but the internal PCB sports a pair of 150 Ω SMD resistors.

I don’t believe the X-axis intercept for a moment, but 1.5 V seems about right for an amber LED.

Oh, and the DMM fuse doesn’t have a ceramic body. You’re seeing the vaporized remains of a 315 mA fuse neatly deposited over the inside of the glass tube after being shorted across a 3 A bench supply.

I hate it when that happens. Replacing it emptied the little bag of those meter fuses; next time it’ll get a half amp fuse.

Bafang BBS02: Assist Power Levels

Although Gee’s Terry Symmetry is sized for female bodies, I managed to ride it up and down the driveway while watching the power display:

Voltage52.5
Rated Current24
Max current18
PowerPower
PASAssistAmpCalcObservedRatio
00%0.000~
14%0.7382669%
26%1.1575292%
39%1.6857892%
413%2.312310485%
520%3.618918296%
630%5.428425891%
750%9.047345396%
885%15.380367584%
9100%18.094590095%
Bafang BBS02 on Terry Symmetry – actual voltage

The variations in the last column suggest my data-taking is … wobbly, at best.

I think the displayed power does not come from actual current and voltage measurements, because recalculating the power using the nominal 48 V battery value produces an unnatural agreement:

Voltage48
Rated Current24
Max current18
PowerPower
PASAssistAmpCalcObservedRatio
00%0.000~
14%0.7352675%
26%1.15252100%
39%1.67878100%
413%2.311210493%
520%3.6173182105%
630%5.4259258100%
750%9.0432453105%
885%15.373467592%
9100%18.0864900104%
Bafang BBS02 on Terry Symmetry – nominal voltage

The motor controller may measure the actual winding currents while generating the BLDC waveforms, but the values may not be available to the display at the end of the cable. If Bafang documented the commands & responses, we’d know for sure, but they don’t.

Those assist values come from Mary’s Tour Easy, a much heavier bike than the Symmetry, but the first few levels work well in my limited tests. The highest levels may be too peppy for Gee’s normal routes, but having some serious boost in reserve can defang (hah) the worst hills.

Terry Symmetry - Tour Easy
Terry Symmetry – Tour Easy

IMO, the bike would burn rubber at the motor’s full 24 A current …

Discrete LM3909: Green and Blue vs. Dead Alkalines

These two discrete LM3909 circuits recently stopped blinking:

LM3909 AA alkaline - Green and Blue
LM3909 AA alkaline – Green and Blue

The green LED (on the left) took six months to wear its pair of not-dead-yet AA alkalines from 2.7 V down to nearly zero.

The blue LED in the radome took two months to go from 1.0 V (!) to nearly zero. It didn’t start very bright and went decidedly dim along the way, but the LM3909 circuitry still managed to jam a few microamps through the LED.

In both cases, one of the cells was reverse-charged by a few hundred millivolts, although neither leaked.

Both got another set of not-quite-dead AA cells and they’re back in action.

A Spider at Breakfast

The underside of a spinach leaf makes a fine place for a spider to guard her egg sac, right up until the leaf arrives on the kitchen cutting board just before breakfast:

Spider guarding egg sac
Spider guarding egg sac

We deported her (and her incipient family) to the flower garden just outside, wished her well, and continued with breakfast.