Dell XPS M1330 Battery Pack Teardown

We had an earlier success tearing down a Dell laptop battery pack, where the six salvaged cells still have 70% of original capacity after ten years of service. However, that was from a laptop that could still boot and run from its battery pack. This XPS M1330 battery pack is in far worse shape. How much worse, we were about to find out.

The first critical detail was realizing the battery pack was not the original Dell battery pack. It is an aftermarket type of unknown manufacture. The earlier battery pack tear down yielded Samsung cells, we’re probably not going to get anything nearly as nice this time around.

Once the case was cracked open the suspicion was confirmed: These appear to be generic 18650-sized lithium cells with no manufacturer branding. The nine cells of the battery pack were divided into three modules in series, each module had three cells wired in parallel. The module in the worst shape exhibited severe corrosion and had no voltage across their terminals.

Corroded 18650

The other two modules were in slightly better shape, but they have self-discharged down to approximately 1 volt DC, well under the recommended voltage range. A web search found some details on what happens to overly discharged lithium cells. In short: the chemistry inside the cell starts dissolving itself. If recharged, the dissolved metals may reform in inconvenient ways. Trying to use these cells has three potential outcomes:

  1. Best case: The metals dissolved into the electrolyte will hamper chemical reaction, resulting in reduced capacity.
  2. Medium case: The dissolved metals will reform in a way that damages the cell, causing it to fail as an open-circuit. (As if no battery was present.)
  3. Worst case: The dissolved metals will reform in a way that damages the cell, but causing it to fail as a closed circuit. Short-circuiting the internals will release a lot of energy very quickly, resulting in high-pressure venting and/or fire.

The corroded cells that have discharged down to zero volts have the highest risk and will be discarded. The remaining cells will be slowly (and carefully) charged back up to gauge their behavior.

Dell XPS M1330 Power Port Salvaged Using Desoldering Tool

Recently a dead Dell XPS M1330 came across the workbench. The battery was dead and the machine fails to boot. After some effort at reviving the machine, it was declared hopeless and salvage operations began. Today’s effort focuses on the motherboard port for the AC power adapter.

Dell Octagonal PowerThe power plug on this Dell different from the typical Dell laptop AC adapter: octagonal in shape rather than round. The shape meant it could not be used on other Dell laptops designed for the round plug. However, the dimensions of the octagon are such that an AC power adapter with the typical round Dell plug fits and could be used to charge the laptop. So while the laptop could be charged with any existing Dell-compatible AC adapter, the AC adapter that came with this machine is specific to this Dell.

Once the XPS M1330 died, its octagonal plug power adapter is not useful for other Dell laptops. It still functions as a power supply transforming household AC to ~19V DC so it might be useful for future projects. To preserve this possibility, the octagonal power port will be recovered from the system board.

The solder used in Dell assembly was possibly one of the lead-free types and is definitely reluctant to melt and flow. Trying to desolder the power port using hand tools (desoldering wick and hand suction pump) had no luck. So this project was chosen as a practice run of using a dedicated desoldering tool, in this case a Hakko 808. The tip of this tool heats up to melt the solder, and with a press of the trigger an electric vacuum pump pulls the melted solder through center channel of the heated tip and into a chamber for later disposal.

The desoldering pump was able to remove more solder than hand tools could, but was still not quite enough to free the port. Using a soldering iron, some user-friendly leaded solder was worked back into the joints to mix with the remaining Dell factory solder. Upon second application of the electric desoldering tool, enough solder was removed to free the port from the system board with only minimal damage.

Desoldering Tool

A test with the voltage meter confirmed this port is now ready to be used to provide ~19V DC power to a future project.

Socket Extraction Success


Disassemble Smoke Detector

One of the smoke detectors in the house has started raising a lot of false alarms and was replaced after a 3:30AM episode. Naturally, we’re going to take it apart. Today’s home smoke detectors come in two types: ionization vs. photo-electric. This particular detector, a First Alert P1210, is a photo-electric detector.

The cover was held on by four screws, only one of which was immediately accessible. The remaining three were blocked by the paper label which was easily punctured for access with a screwdriver.

Smoke Detector Lidless

Inside the plastic housing is a surprisingly large circuit board, its battery, and piezoelectric alarm buzzer. A cursory examination of the circuit board revealed some pads for absent components, which likely meant this board is shared with higher-end models with more features. Beyond those empty pads, almost a third of the circuit board real estate serves no apparent purpose.

The brains of the operation is a single chip printed with the Microchip logo which made it easy to look up its datasheet. A search on its numbers identified it as a Microchip RE46C190 which is apparently a turnkey solution for anybody to build a smoke detector around the chip.

Smoke Detector Sensor and Baffle

The nose of the operation is an infrared LED paired with a detector, kept in a housing that keeps the detector out of direct line of sight to the LED. When smoke particles enter the detection chamber, it will be illuminated by the LED and reflect light into the detector.

There is no obvious indication of why this smoke detector started sounding false alarms. Perhaps some dust entered the detection chamber? A smoke detector chip shouldn’t sound the alarm for just any reflection, it should look for specific characteristics of smoke particles. But there’s a chance we are expecting too much of this little detector.

And even if it does panic at any reflection regardless of source, the knowledge is not particularly helpful. The detection chamber and the baffles surrounding it is not accessible for cleaning without taking the detector apart.

For the immediate future, these parts will sit in a plastic bag. Added to the stockpile of electronic parts for potential future projects.

Disassemble Old Cordless Drill

While working on my NEXTEC Dustbuster project, I took the work-in-progress to various local maker meets to as a show-and-tell subject. This inspired another local tinkerer to bring a really old cordless drill for a compare-and-contrast session. It hasn’t run in years so nothing was risked by taking it apart. Which we did.

Old Cordless Drill

We see a motor that’s roughly in the same class as the motor in my Dustbuster. Instead of an air-moving fan directly attached to the motor output shaft, we have a simple reduction gearbox instead of the planetary gear popular with modern counterparts. Other missing convenience features common in current generation products include a torque-sensitive clutch and key-less chuck.

The most surprising part of this old design is how they implemented the two-speed mechanism. The trigger moves a switch into one of three positions corresponding to “off”, “low”, and “high” speed. Obviously “off” is an open-circuit and “high” speed connects all five (six?) battery cells to the motor. It’s the “low” that was a surprise – as far as we can determine, it connects three of the battery cells to the motor and bypasses the rest. This will certainly send less power into the motor, but it also results in uneven discharge pattern for the battery cells. Such behavior is considered absolute no-no with modern lithium-ion battery cells, and it couldn’t have been very healthy for these old NiCad cells, either.

In theory this drill could be revived with a battery transplant, or maybe upgrade to two-cell Lithium-Ion power. Whether it’ll happen depends on the owner, who should definitely find an alternative implementation for variable speed.

Disassemble NEXTEC LED Work Light

Today’s project is to disassemble the NEXTEC LED work light and see if we can use it to adapt an old Black & Decker BHD9600CHV Dustbuster to lithium-ion power.

The wish list of the disassembly operation are:

  • Battery compartment: If we could use the battery compartment of the work light, don’t have to reverse engineer the dimensions of the battery pack and the slots needed to clip the battery in place.
  • Battery connector: If we could use the battery connector of the work light, we don’t have to reverse engineer the precise location and dimension of the metal contacts for drawing power from the battery.
  • Battery over-discharge protection: Unlike Ni-Cad batteries’ tolerance of discharge, over-discharging lithium-ion cells could cause permanent damage. As a result, most lithium-ion devices have a protection circuit and I’d like to pull that in.

The things we don’t care about:

  • LED array: There are plenty of LEDs of all color and brightness on every electronic tinkerer’s workbench. One fewer array would not be missed.
  • Switch: The work light’s switch is the type where a press closes the circuit, then another press opens the circuit. This is the right behavior for a light but not for a vacuum. Also: this switch was designed for a low-amperage LED and while it looks sufficiently beefy, it might not tolerate the amperage draw of a Dustbuster motor.

With these goals in mind we start with the obvious task of removing the four visible screws. After the screws were removed there was one more fastener: a small metal C-clip holding the two halves together near where the pinkie finger rests while holding the light. The clip was designed to require a specific tool for a clean removal. For people who are unconcerned about cosmetic damage, it could be persuaded to abandon its post with pliers.

Work Light Disassembled

Looking at the disassembled light, we see we can easily re-purpose the battery compartment and associated battery connector for the project. The third item on the wish list – the over-discharge protection circuit – is unfortunately incorporated onto the LED circuit board and not an easily separated part. We’ll just have to be careful when using the upgraded Dustbuster and not discharge it too much.

Having the battery compartment and electrical contacts is great. It bypasses a lot of iterative CAD work and 3D printing to pin down proper dimensions to fit the battery. The next step is to join the two devices together.

(Cross-posted to

No AC Adapter, No Problem! Alternate Power Source for an Acer Aspire Switch.

Once I was done gawking the clever magnetic attachment mechanism of the Acer SW5-012, it’s time to get back to trying to get it to run. The machine was able to power up on its remaining battery power for a little bit, but now it needs more juice. Since I was given this computer in nonfunctional “as-is” state, the AC power adapter was not part of the package.

Disinclined to spend any money on this machine, but willing to spend time, I went online to look for information about the AC adapter. Unfortunately there appeared to have been several similar but different computers sold under the “Acer Aspire Switch 10” name. And while it’s unclear if all of them use the same AC power adapter, the adapters were consistently stated to be an unit that outputs 12V DC.

This is great news as I have many ways to deliver 12V DC among my collection of tools and parts. But I have no plugs on hand that fits the existing power socket. I examined the power connector to the motherboard and saw four wires. A continuity check confirmed that it’s a simple positive terminal and ground terminal, with a pair of wires electrically connected for each. None of the wires are electrically distinct from power, so I don’t have to worry about data handshaking signals that are involved in charging certain other laptops.

Armed with this information, I removed the existing 12V power socket and the associated bracket. I cut the wire connecting the socket to the motherboard and soldered a JST RCY connector in its place.

Acer JST RCY adaptation

This type of connector is popular with remote-control aircraft and frequently used to carry roughly 12 volts (3-cell lithium rechargeable battery) at up to 3 amps. I reassembled the tablet, connected a 12V power source, and was reassured by illumination of the charging activity light. After a few hours, the tablet was charged up and ready to go again. Success!


Functional Simplicity of the “Acer Smart Hinge”

Yesterday’s post was about trying to bring an Acer SW5-012 back to life, which was fortunately as easy as reseating a ribbon cable. One of the reasons I was so eager to crack that thing open was my fascination with its hinge attachment mechanism. This was one of the “convertible” machines launched in the Windows 8 era and evolution of the category continued to this day with computers like the Microsoft Surface Book.

The hinge attachment/release mechanism for the Surface Book featured precisely machined components and electronics to control a wire of memory alloy. This Acer is a much cheaper machine so its nifty connector must also be simpler. Before I pried it open, I mentally tried to figure out how I would design such a mechanism.

At the time I thought the battery was flat, so I excluded any electronics in the design. It had to work without power, which made me think about magnets. A few small magnets to detect when the base is close to the screen, and pull against some spring-loaded arms to hold the thing together. When I pull on the screen, the force overcomes the springs to releases the arms.

Once I popped off the back cover of the computer, I could check my design against the answer and… well, I got the magnets part right even though it was based on a false premise (the battery was not flat like I thought.) And all the spring-loaded arms and clips and levers? Unnecessary complexity. I knew it had to be simpler than the Surface Book mechanism, but it was far simpler than what I imagined.

The actual mechanism consisted of magnets and… that’s it. Just some very cleverly placed magnets. When the screen is installed on the base, the magnets attract like we expect them to do, holding things together.

Acer Hinge Engaged

So what happens when we lift the screen away from the base? What’s causing that mechanical “click” sound?

When the base is lifted, the magnets in the screen is pulled away from the magnets in the base. Lacking the strong attraction, the magnets in the screen searched for the next best thing and finds a few metal plates slightly recessed into the cavity. The “click” is the magnet moving from the no-longer-there base magnet to the metal plate. When the magnets are attached to this inner metal plate, they are a few millimeters away from the edge of the unit but that’s far enough to keep it from picking up errant metal bits (paperclips, staples, etc.) while it is in tablet mode.

Acer Hinge Released

When the screen is reinstalled on the base, the screen magnet leave the metal plate in favor of the magnet in the base, making another “click”.

The Acer manual called it the “Acer Smart Hinge” and I agree it’s very smart – on the part of the people who designed it. Its simplicity lends to lower manufacturing cost and also to its reliability – no springs to break, no latch to wear out.

I am impressed.

Acer Aspire Disabled By Loose Cable.

I recently received an old Acer Aspire Switch 10 computer that no longer ran: there was no response when pushing the power button. The most obvious hypothesis is that the batteries are flat and need to be charged. Unfortunately, my gift of the computer did not include its matching AC power adapter.

If I was confident that was the only issue, I would go out and buy a power adapter. But I didn’t know if there were more serious problems in this machine and didn’t want to throw money at an unknown quantity. Besides, I received this computer on the premise that I wanted to take it apart for fun, so that’s exactly what I’m going to do.

Putting its serial number into Acer’s support site told me the model number (SW5-012) and part number (NT.L4TAA.018), but no service manual. I’m spoiled by Dell who usually releases a service manual detailing how to take apart and service a computer. Apparently Acer does not follow the practice.

There were no obvious external fasteners I could loosen, so I started prying at the visible seams to see if I could release plastic clips. Once I had three loose, the remainder (~25 in all) easily popped off in sequence.

My target was the battery module which I planned to remove and charge directly. Removing the battery required removing several pieces of tape. Some of these pieces of tape were applied over connectors, presumably to help the cables stay in place. One of these cables traversed the length of the battery so I had to remove the tape and the cable to free the battery. After I carefully peeled off the tape, I reached out to disconnect the cable and… it fell off freely.

Hmm, that wasn’t supposed to happen.

This cable connects the motherboard on one side of the machine to a small circuit board on the other side. The small circuit board hosts the Windows button, the volume up/down buttons, the headphone jack, and… the power button. If this cable was disconnected, it would explain why pushing the power button had no response.

Acer Power Ribbon

Since the battery was accessible now, I checked its voltage: 4.01V. Comfortably above the ~3.7V nominal voltage of a lithium-ion battery so the problem with this computer was not a dead battery. Maybe it’s the loose cable I just came across? I reinstalled the cable and pushed the power button again.

And… it’s alive!

Disassemble Monoprice Maker Ultimate (Wanhao Duplicator 6) Failed Relay

This is the main 24V relay on the control board of my Monoprice Maker Ultimate 3D printer, which is a rebadged and lightly modified variant of Wanhao Duplicator 6. An earlier blog post figured out why it died. (Short summary: the printer design drove this relay beyond its rated limit of 10A @ 24V.) Today let’s look closer at how it died.

There were clear visual indication of relay failure in the form of a heat-distorted casing with a hole melted into it.

Relay 10 - ClosedThere were no fasteners to release so the case had to be cut free from the base. Once the case was removed, we could see the guts of the relay.

Relay 20 - OpenLooking at the inside of the just-removed case, we can see a lot of heat damage. Black char marks the hottest areas, and discolored white marked the rest.

Relay 40 - Charred CaseIt’s a fairly straightforward relay, with the coil actuating an armature moving between contacts on either the plate above or below it. The armature+contact area is immediately behind the blacked charred bits of the case. And looking at the armature and contacts themselves, we see the relay died an unhappy death.

Relay 30 - Distorted ContactEverything in the contact area is distorted and/or charred. There is a black plastic-feeling piece holding everything in position relative to each other, and it could no longer do its job with heat distorting it and moved things out of alignment. Between the armature and the bottom contact is a blob of melted something that looks vaguely like solder. The bits of blue visible are parts of the blue casing that has melted onto this assembly. While the top contact looks OK in this picture, the side facing the armature is just as blackened and charred as the visible face of the bottom contact. The armature itself is barely visible here but it is actually discolored and distorted near the contacts.

From the Facebook user’s group, I’ve learned more recent revisions of the printer used a relay from the SRU product line to replace this SRD unit. I’m still trying to find a data sheet for the newer relay. I would hope that it is a drop-in replacement rated for at least 15A @ 24V, preferably 20A. And hopefully it would not die like this SRD-05VDC-SL-C relay did.

Disassemble Broken Garbage Disposal

A few weeks ago something under my kitchen sink started leaking water. I had hoped it was a simple plumbing failure that would be easy to fix. Perhaps a pipe has come loose or cracked a seal? Sadly this was not the case. Water was dripping off the bottom of the garbage disposal and its exterior was dry all around: Water was flowing through the interior of the garbage disposal which meant its useful service life has come to an end.

Before I dispose of the disposal, I wanted to cut it open to see exactly what failed. I guessed that a water seal has failed around the main motor shaft, and wanted to see if my guess was correct. But first, it was sent to sit in the garage and dry off.

Disposal 10 - StartLooking around the perimeter for fasteners, the four rods immediately stood out. They are spread around the perimeter, and almost the entire height of the disposal. I tried the easy thing first but they refused to budge with my flat-head screwdriver. So out came the angle grinder with the cutting wheel, which quickly cut the exposed shaft.

Disposal 15 - Severed rodUnfortunately that did not allow the top part to come free. Something else was holding it together. Whether it is a mechanism I don’t understand or corrosion I could not tell. But there were no other obvious fasteners to release on the top side, nor is there a convenient point to start prying.

So I started looking around the bottom end of the disposal, where there was a window cut into the bottom for wiring to enter the device. That allowed me to look inside to scout out where I could best use my cutting wheel to cut the bottom free.

Disposal 20 - Bottom openedOnce the bottom was cut free, I had a better view to find next best place to cut the stator free. When I pulled the stator off, I was very surprised to feel the rotor flex along with the stator because I had expected it to stay with the rest of the grinder.

Disposal 30 - PerforationThe source of the problem became clear once the stator came off: the metal plate separating the electrical motor from the grinder has been severely weakened by corrosion. I’m sure there were only a few (or maybe only one) hole when I pulled this from the sink, but the whole plate was corrosion weakened so it fell apart when I pulled the stator off the bottom.