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.

Category: Photography & Images

Taking & making images.

Dell 75UYF Battery Teardown: Cell Capacity

Putting that battery into the Dell 8100 laptop produced the dreaded blinky light of doom, so it has been on the shelf for maybe half a year. Having gutted the cells from the case, the next step was to discharge the cells completely, thereby producing the lower four curves in this plot:

Dell 8100 Laptop Battery Cells

I arbitrarily labeled the cell pairs 1 through 4. Pair 1 has the lowest remaining charge and the other three seem very closely matched.

I recharged the four cell pairs one-at-a-time from a bench power supply set to 4.2 V. Each pair started charging at about 2 A, somewhat lower than the pack’s 3.5 A limit, so the supply’s 3 A current limit didn’t come into play. You probably don’t want to do this at home, but …

The usual charge regime for lithium cells terminates when the charging current at 4.2 V drops below 3% of the rated current (other sources say 10%, take your pick). The pack’s dataplate sayeth the charging current = 3.5 A, so the termination current = 100 mA. I picked 3% of the initial 2 A current = 60 mA and stopped the charge there, so I think the cells were about as charged as they were ever going to get.

As nearly as I can tell, increasing the voltage enough to charge at a current-limited 3.5 A (a bit beyond my bench supply’s upper limit, but let’s pretend), then reducing the voltage to 4.2 V as the current drops would be perfectly OK and in accordance with accepted practice, but I’m not that interested in a faster charge.

Unlike the other three pairs, Pair 1 quickly became warm and I stopped the charge. Warming is not a nominal outcome of charging lithium-based cells, so those were most likely the cells that caused the PCB to pull the plug on the pack. The other pairs remained cool during the entire charge cycle, the way they’re supposed to behave.

However, even with that limited charge, Pack 1 had about the same capacity as the (presumably) fully charged Pack 2, showing that the cells get most of their charge early in the cycle. Pairs 3 and 4 had more capacity, but they’re not in the best of health.

The blue curve in this graph shows the discharge curve for the 1.1 A·h Canon NB-5L battery (actually, a cell) that came with the SX230HS camera:

Canon NB-5L – first tests

Notice that it remains above 3.4 V until it produces 1.1 A·h at 500 mA, which is roughly its rated capacity. The other traces come from those crap eBay NB-5L batteries.

The two best pairs of Dell cells can each produce about 1.3 A·h at 1 A before dropping below 3.4 V (the cursor & box mark that voltage in the top graph), so they’re in rather bad shape. Strapping the best two pairs together would give a hulking lump with perhaps three times the life of the minuscule NB-5L battery, so I think that’s probably not worth the effort.

Particularly when one can get a prismatic 3.7 V 5 A·h battery for about $30 delivered, complete with protective PCB and pigtail leads…

2012-06-22
Dell 75UYF Battery Teardown: Part 1

One of the batteries on the ancient Dell Inspiron 8100 laptop died completely and our Larval Engineer reports the other battery isn’t far behind; it gets her from outlet to outlet and not much more. Pursuant to that comment about harvesting reasonably good cells from dead batteries to build an extended-life external battery for the Canon SX230HS camera, I made a preliminary pack probe.

The label says it’s a 14.8 V battery, so you’d expect four 3.7 V lithium cells in series. The 3.8 A·h capacity suggests parallel cells:

Dell 75YUF battery – label

Indeed, peeling off the label shows four cells pairs in series:

Dell 75YUF battery – under label

The case joint seems firmly welded together and resisted simple attempts to crack it open. I might run a slitting saw around the edge, although I’ll probably just crunch it in the vise because the patient need not survive the operation.

A single cell should have a 1.9 A·h capacity, although in an awkward cylindrical form factor. The 3.5 A charging current would drop to 1.7 A for a (string of) single cells.

The Canon SX230HS uses a single 3.7 V, 1.1 A·h prismatic “battery”, which means replacing that with a single external cell wouldn’t be a major win; the size difference shows how much lithium energy storage tech has advanced in the last decade or so. A pair of cells in parallel would quadruple the runtime, which might be enough. Three in parallel would be fine, although that would require attention to matching their capacity; the nominal 5.2 A charging current (1.5 × 3.5 A) seems aggressive.

Time to start mulling charging circuits…

2012-06-11
Sony NP-FS11 Battery Rebuild Repair

One of the battery packs I’d re-rebuilt failed in short order, which I wrote off to a bad cell and tossed it on the heap. Having recently found a small stack of Round Tuits, I’ve been cleaning off the bench and took the pack apart again. Turns out I blundered the solder joint between the positive cell terminal and the protective circuit board: the strap in the foreground joining those two points didn’t make a good connection to the cells.

I suppose it was just another cold solder joint:

Rebuilt NP-FS11 battery – Pack A

That’s an awkward joint at best, because the protective circuit doesn’t come willingly out of the housing and you (well, I) must solder it without scorching the cells, the plastic case, or the PCB. It can be done, but it’s not easy.

Charged it up and it’s back in the A/B/C pack rotation again.

Memo to Self: Tough to find good repairmen these days, eh?

2012-05-29
Macro Lens Focus Stacking
Begin by mounting the Canon SX230HS on the macro lens adapter, zooming to about the maximum, fiddling with a ruler to put the end at the closest focus point, and eventually get an overall view like this:

Ruler – macro mid-focus

The images below were batch cropped from similar views with ImageMagick:
```
for f in $(seq 17 22) ; do convert -crop '1500x1126+1900+1800' \
   img_18${f}.jpg img_18${f}-crop.jpg ; done
```
Yes, I’ve taken a bit over 1800 images since getting that camera… the old DSC-F505V recently rolled over at 10K images.

Take a set of six identically exposed pictures starting with the focus at infinity (about 95 mm in real life):

macro far focus

And ending with the closest focus at about 1 meter for this zoom setting (and 80 mm in real life):

macro near focus

Then apply enfuse (from the Ubuntu repositories) with a handful of parameters suggested there that combine the sharpest parts of each image into a single image:
```
enfuse --verbose --exposure-weight=0 --saturation-weight=0 \
   --contrast-weight=1 --hard-mask --output=stacked.jpg \
   img_18??-crop.jpg
```
Which produces this nice result:

Ruler – macro combined focus

It’s not perfect, it needs a few more intermediate images, there’s fringing around high-contrast edges, and so forth and so on, but for a first pass it ain’t bad at all.

I bar-clamped the camera & macro adapter to the desk in order to eliminate all motion. My usual tripod mount for the macro setup isn’t all that stable and the microscope stand isn’t particularly rigid, either, so I must improve a bunch of mechanical structures. In principle, you can post-process the pictures to realign them, although the tolerances seem daunting enough to make mechanical fixturing look downright attractive by comparison.

Now, if it should turn out that the SX230HS supports the CHDK USB remote trigger, that’d be nice. Or maybe the right way to proceed involves converting the problem to A Simple Matter of Software by writing a CHDK script that tweaks the focus by multiples rather than increments.
2012-05-28
Canon Hack Development Kit for SX230HS

Although the macro lens adapter and microscope mount work well enough, the relatively small sensor and lens in my Canon SX230HS make for a razor-thin depth of field:

Macro lens depth of field

Those are, of course, millimeter divisions on the ruler.

A bit of rummaging leads to the notion of Focus Stacking, which involves taking a sequence of images with identical exposure settings and different focus points, then compositing the in-focus parts of each image to produce a single image with everything in focus. Although some examples show a manual process involving layers in, say, The GIMP or Photoshop, I think an automated process would be better.

Given that I have a Canon SX230HS camera, the first step is to download the proper version of the Canon Hack Development Kit, unpack it onto a spare SD card, and get used to it.

As it turns out, the focus bracketing works exactly as intended, but doesn’t do quite what I need: it changes the focus in linear steps by adding a constant bracketing distance. The macro lens adapter drags the “infinity” focus point inward to maybe 15 mm beyond the innermost focus point, but the camera’s focus range still shows 1 m to ∞. Stepping in 1 m increments generates a bazillion pictures that don’t differ by much at all after 5 m, but you still need a few near the far end.

However, it seems the only way to get a bazillion pictures is by holding the shutter button down with the drive mode set to Continuous, as the camera’s Custom Timer mode has a 10 shot upper limit. If I must do that, I may as well adjust the focus manually: the assumption being that the camera shall be firmly mounted to keep the pix in alignment, which currently isn’t true in any of my setups and certainly won’t be true with my finger on the button.

The camera already has exposure bracketing, although not to the extreme range available through CHDK. RAW images (or the roughly equivalent DNG format) might come in handy at some point, but right now they’re just a temping digression available only through CHDK.

If I’m going to keep using CHDK, I must conjure up an artificial NB-5L battery with an external power source. Those cheap eBay batteries work fine for the usual duty cycle, but constant zooming & focusing & suchlike chew them pretty hard…

2012-05-27
Gas Flareoff

While I was on that ride, I found this at the bottom of a smoky pillar rising along the Hudson River:

Turns out Central Hudson Gas & Electric has a pipeline under the Hudson at that point and I’d admired their spherical storage tank from ground level some years back:

Gas Storage Tank

I don’t know what they’re flaring off, but it looks messier than, say, propane. There’s another flare nozzle just out of the picture on the lower left, both along the edge of the circular concrete pad left over from a cylindrical storage tank, so they do this often enough to have some permanent infrastructure.

2012-05-26
Ladybugs!

These freshly hatched alligator-oid critters:

Ladybug larvae

…. quickly become something even more fearsome, at least to aphids smaller than they are:

Ladybug Larva Eating Aphid (by Cheryl Hearty – CCE/DC)

Eventually they turn into Ladybugs who relentlessly stalk larger aphids on garden plants:

Ladybug with aphids

And then they do this and the wheel goes around:

Ladybugs mating

Gardeners love them ever so much…

2012-05-19