This is the Amp Hour, released September 14th, 2025.
Episode 702, Test Point Acupuncture.
Welcome to the Amp Hour. I’m Dave Jones from the EEVblog.
And I’m Chris Gamble of Contextual Electronics.
Dave’s Refurbished Microsoft Surface Issues
Dave shares his frustration with a recently purchased refurbished Microsoft Surface laptop that exhibited multiple faults requiring its return.
Battery Charging Fault
The laptop arrived with approximately 70% battery charge and was expected to have around 85% battery capacity remaining from its original specifications. However, after plugging it in to charge overnight, the battery discharged to 40% instead of charging to 100%. Windows indicated the device was charging, and the charging LED illuminated, yet the battery continued to drain until hitting 40%, then charged back up to 50% and remained flat at that level.
Multiple chargers were tested, including a separate Microsoft Surface charger, ruling out a faulty power supply. Dave generated a diagnostic battery health report that confirmed the capacity loss, though batteries should still indicate a full 100% charge regardless of degraded capacity.
Power Button Malfunction
An additional fault involved the power button requiring a 10-second hold for a cold boot every time, further indicating hardware problems. The device was returned due to these combined issues.
Chris’s Tesla Powerwall Home Energy System
Chris provides an update on his home’s Tesla Powerwall system, which is now functioning as an appliance after resolving an initial setup issue.
Powerwall Setup and Initial Loose Wire Fault
The system had been provisioned but was not operating properly after installation. The Powerwall had charged to 100% but was not discharging. The issue was traced to a loose RS-485 wire connecting the battery and inverter unit (located in the garage) to the controller box (located at the front of the house near the main electrical panel).
Integrated Inverter and Separate Control Box
Dave initially assumed the Tesla Powerwall was a fully integrated single-box solution. In reality, while the charger, inverter, and batteries are integrated into the main unit, there is a separate controller box that manages switching between grid power and battery backup. This controller contains smart switches that determine when to back-feed power into the panel. Dave noted the impressive engineering quality of Tesla’s hardware implementation.
Powerwall Performance and Seasonal Impact
With the system operational, Chris now monitors energy generation through the Tesla app. Solar generation has been lower than anticipated, though this is partially attributed to seasonal factors—trees surrounding the property block sunlight during certain times of year. The system is expected to provide more value as utility power becomes more expensive and as autumn approaches and tree coverage decreases.
Side Tangent: Veggie Pods and Solar Angle
The hosts briefly discussed veggie pods for home gardening, noting that recent tree trimming has improved sun exposure on their property, potentially making vegetable cultivation more viable.
Discussion on Power Rates and Nuclear Energy
Power Costs: US vs. Australia
Chris investigated electricity rates and found significant regional differences. His location in North Carolina benefits from approximately 70% nuclear power generation, resulting in electricity costs of approximately 12.5 to 13 cents per kilowatt hour. By comparison, Dave’s electricity in Australia costs around 35 cents per kilowatt hour (approximately 23-25 US cents).
The highest US rates include:
- Hawaii: 41 cents/kWh
- California: 38 cents/kWh
Nuclear Energy Policy
The conversation touched on nuclear energy bans in Australia at both federal and state levels. Dave noted that even with private funding, new nuclear plants cannot be constructed due to these prohibitions. They discussed Germany’s decision to decommission their nuclear plants and the difficulty of restarting nuclear programs once shut down.
Nuclear Waste Generation and Storage Solutions
Chris researched nuclear waste generation, discovering that plants produce approximately 50 to 77 metric tons of spent fuel per year per plant (based on 20-30 metric tons per gigawatt annually). While this exceeded their initial expectations, they noted that volumetrically this represents a relatively small amount—perhaps 10 barrels per year per plant.
Storage solutions were also discussed. Contrary to popular perception perpetuated by media such as The Simpsons, spent fuel can be safely stored on-site in concrete containment structures without significant radiation exposure to nearby personnel. Groundwater contamination represents the primary environmental concern.
North Carolina’s Energy Generation Mix
Duke Energy’s generation mix for North Carolina consists of:
- Nuclear: 53%
- Natural gas: 33%
- Coal: 9%
- Hydro: 1.3%
- Solar: 2%
The hosts expressed surprise at the high natural gas percentage, though this reflects broader trends in US energy production leveraging fracking and shale resources.
Grid Stability, Duck Curve, and Battery Solutions
Grid Challenges and the Duck Curve
A previous guest from the Department of Energy (DOE) explained the duck curve concept—energy usage patterns throughout the day—and the role of peaker plants in meeting demand spikes.
Chris observed that his battery system typically carries his household from noon (when solar generation exceeds consumption) through approximately 8 or 9 PM, effectively bridging the duck curve dip. However, on sunny days when the battery reaches full capacity by 3 PM, excess solar generation has nowhere to go and is exported back to the grid. This creates grid stability challenges when many solar-equipped households simultaneously dump excess power during peak production hours.
Australia’s $2 Billion Battery Scheme
Australia’s government announced a $2 billion battery scheme providing batteries to consumers, including those without existing solar installations. This initiative addresses the country’s status as having the world’s largest uptake of home solar (approximately 50% of houses), which has created excess generation capacity with insufficient storage. The scheme aims to remove households from the duck curve equation and provide distributed grid storage.
Smart Solar Inverters and Remote Grid Control
Grid stability issues stem partly from the prevalence of “dumb” inverters in Australia’s early solar adoption. Smart solar inverters capable of remote control by grid operators could solve excess generation problems by allowing operators to temporarily shut off solar feed-in when the grid is overloaded. This effectively moves the operating point down the IV curve—implementing Minimum Power Point Tracking rather than Maximum Power Point Tracking. New battery installations require inverters with future remote control capabilities.
Dave’s Home Battery Expansion Challenges
Firmware and Gateway Issues
Dave’s home battery system experienced issues with one of five battery modules switching off unexpectedly. After consulting with Peter (the battery designer, previously a podcast guest), the problem was attributed to early beta firmware requiring updates. Dave accidentally damaged two Ethernet gateway devices while attempting remote firmware updates, necessitating replacement with a 4G modem interface.
The cells themselves remain healthy; the issue appears to be firmware-related, likely due to Dave being an early adopter of this battery model.
Off-Grid Capability and Inverter Limitations
Peter recommended configuring the system to power the entire house from the inverter, switching to grid only when necessary. However, Dave’s current Deye inverter is limited to 8 kilowatts maximum output, insufficient to power all-electric appliances simultaneously (including EV charging). Dave plans to replace this problematic inverter when expanding the system.
Resistive Water Heater and Powerwall Exclusion
Dave’s home uses a resistive electric water heater rather than a heat pump, which represents an inefficiency given his battery system. Replacement with a heat pump water heater is planned for the future. His 20 kilowatt-hour battery configuration provides current capacity needs.
Garage Apartment on Separate Sub-Panel
Chris’s garage apartment is on a separately metered sub-panel not backed up by the Tesla Powerwall. The Powerwall only connects to the main house sub-panel. This arrangement means EV charging and garage apartment usage are not supported during grid outages.
Time-Sensitive Free Power Window
Dave’s electricity provider offers three hours of free power daily (11 AM to 2 PM), a scheme enabled by Australia’s massive solar uptake and excess generation capacity. The household has implemented timers to activate high-draw appliances during this window, including:
- EV charging
- Pool pump operation
- Heat pump operation
- Hot water system
- Dryer (as needed)
Batteries are also charged during this free period. This lifestyle adjustment is feasible because his partner works from home and can manage appliance scheduling. The hosts discussed how this model might eventually spread to US sunbelt states as solar adoption increases.
Electronics Repair Stories
Tennis Remote Keypad Repair (Silver Migration)
Dave repaired a tennis court remote control with a membrane keypad where four of five key rows had failed. Initial investigation suggested a standard flex cable break, but closer inspection revealed the cable used silver conductive ink traces rather than copper. The silver had migrated or tarnished across four traces—a failure mode Dave had not previously encountered to this extent. There was no evidence of water ingress or flexion stress at the failure point. The repair involved repainting the traces with silver conductive paint, restoring functionality.
Chris’s Test Point Design Flaw (Acupuncture)
Chris discussed learning a lesson about test point placement through painful experience. He placed two 1-millimeter test point pads adjacent to each other without adequate spacing, creating difficulties for test jig construction using pogo pins. The resulting test fixture required “precision acupuncture” techniques to contact both pads simultaneously, involving angled drilling and creative 3D-printed solutions with hot glue. This experience reinforced the importance of properly sized, well-spaced test points on PCBs—a lesson repeatedly emphasized on the podcast but only truly learned through direct experience.
Soldering Iron Tip Injury and JBC Tips
Dave injured himself by accidentally pressing his hand onto new JBC soldering iron cartridges stored in a holder. The conical tips are needle-sharp and penetrated his finger deeply enough that a cartridge remained embedded in his hand. The incident highlighted the extreme sharpness of fine soldering tips designed for micro-fine work on components as small as 01005 packages.
Dave purchased a smaller JBC handle and fine tips for detailed work but opted for third-party eBay cartridges rather than genuine JBC tips given the limited expected usage. He expressed admiration for JBC’s nano soldering iron designed for extremely small components.
Expert Repair Channels (NorthridgeFix, Adam Savage’s Tested)
The hosts acknowledged their limitations as generalists compared to dedicated repair technicians. They highlighted NorthridgeFix as an exemplary repair channel performing detailed comparisons of solder flux, solder wick, and other consumables. Professional repair technicians have dedicated tool setups, schematic access, and board view software enabling efficient work that occasional repairers cannot match.
Dave mentioned that Adam Savage (of MythBusters fame) reportedly learned soldering from one of his videos, highlighting the reach of educational content despite not being daily practitioners.
Multimeter Reviews and Design Viability
ANENG 626 Handheld Multimeter
Dave reviewed the ANENG 626 multimeter, a device with an unusual form factor resembling a tape measure. The hosts debated whether the enclosure represented custom tooling or modified existing molds. Dave ordered the device out of curiosity despite recognizing its poor implementation, describing it as occupying an uncanny valley between novelty and functionality.
Morbid Fascination: Wrist-Worn Multimeter
Dave also ordered a wrist-worn multimeter from AliExpress (approximately $10) with fixed leads, acknowledging it would be functionally terrible but driven by morbid fascination with the concept.
Minimum Viable Build Number for Custom Multimeter Tooling
The discussion turned to manufacturing economics for niche electronic products. Dave shared insights from developing his 121GW multimeter with Arcane, where initial estimates suggested 3,000-4,000 units would make a custom multimeter viable. However, he suspected modern Chinese manufacturing capabilities might enable profitability at volumes as low as 500-1,000 units through:
- Mold modification rather than custom tooling
- Soft alloy molds machined on five-axis machines rather than hardened steel
- Marketplace acquisition of cast-off molds with welded modifications
The hosts speculated that products like the ANENG 626 likely reuse or modify existing toolings (such as laser tape measure enclosures) rather than employing fully custom designs.
Chris’s Micro Timer Project
Higher Resolution LCD and Processing Penalties
Chris is developing a low-power timer project using an LCD display from Good Display (note: company logo stylizes as “Goo Display”). While seeking a Sharp memory LCD alternative, he found a higher-resolution display (360x240) that offers more pixels but requires increased memory and SPI bus data rates to update. This creates a power consumption trade-off, as the original vision of a slow, low-power processor may be insufficient to drive the display efficiently.
Processor Choice: ESP32 for Flexibility
The demo board shipped with an ESP32, leading Chris to consider incorporating Wi-Fi and Bluetooth capabilities despite the power penalty. Making the device hackable and extensible—beyond a simple fixed timer—could appeal to a broader market. Potential applications include:
- Network time display
- Data logging and transmission
- Gaming applications
The ESP32’s programmability and ecosystem support (Arduino, MicroPython, ESP-IDF, Rust, Zephyr) make it attractive for an open, hackable device.
Software Ecosystem: Arduino vs. ESP-IDF
Chris’s demo board currently runs Arduino code. While Arduino offers accessibility for beginners, ESPIDF or other frameworks would provide better power optimization for a battery-powered device. However, releasing Arduino-based firmware allows users to fork and port to preferred platforms (Rust, bare metal, etc.) without limiting the hardware’s potential applications.
18650 Battery and Power Optimization
The design incorporates an 18650 battery holder directly on the PCB, enabling user-replaceable batteries rather than integrated pouch cells. Charging occurs via external USB. The battery fits neatly behind the angled display, matching the form factor requirements.
Power optimization strategies include using interrupt-driven wake cycles (as demonstrated by YouTuber Kevin Darrah), where the processor sleeps and wakes once per second to update the display before returning to sleep.
Conclusion
The hosts concluded the episode, noting they had exceeded their scheduled time. Chris planned to continue work while Dave prepared for sleep, maintaining their opposite-side-of-the-planet schedule dynamic.