#### System Description - Joule thief circuit - Diode into some super capacitor thing - Pulsed LiPo Charging? - The most important part here is the intermediate energy buffer that stands between the joule thief and the BMS ##### Precision and Budget Considerations Considering that ChatGPT keeps recommending me $2000 pieces of bench kit I should probably figure out what level of precision I'm going for. I can estimate the energy content of a battery, the remaining unused content, to 100J/1kJ/10kJ and then extract it to a similar level of precision The first pass MVP needs to be simple and imprecise to prove the concept #### Shopping List Looks like I can get started for under $200 ##### Joule Thief Parts - Battery Tester - https://a.co/d/61ORCQq - https://a.co/d/91lB8wt - Ferrite Cores - https://a.co/d/4mBZxS0 - https://a.co/d/8rBXIkq - https://a.co/d/hxaLM8Z - https://a.co/d/iTQFP4V - https://a.co/d/fLa8GC2 - Enamel Wire for Winding - https://a.co/d/eDksbOC - https://a.co/d/hL46Cwo - https://a.co/d/0GKYTLp - Supercapacitors - https://a.co/d/9ySBNfb - https://a.co/d/5RFjvUN - https://a.co/d/0oAfXnG - 18650 Cells - https://a.co/d/7uOzpsw - https://a.co/d/8czHoza - 18650 Charger/Tester - https://a.co/d/fi6lFru - 18650 Plastic Spacers - https://a.co/d/5eErUtf - Spot Welder - https://a.co/d/84WDMNk - https://a.co/d/8MMGL60 - Nickel Ribbon - https://a.co/d/hlIxFw1 - BMS Board/s - https://a.co/d/8NGtBNl - Heat Shrink Vinyl Wrap - https://a.co/d/dCHHTDO - Bullet Plug Connectors - https://a.co/d/423AwKk #### Research Questions - What kind of intermediary stage should be going in between the petty generator and the BMS for charging to buffer and condition this energy? - What goes into high-quality battery monitoring & diagnostics? - How are diagnostic practices different for rechargeable and non-rechargeable batteries? - I need to be able to accurately and precisely evaluate used non-rechargeable batteries (UNRB's) so I can predict how much energy my system will be able to extract from them in order to characterize my design's efficacy. - What's an RTD? - Overview of Electrochemical Impedance Spectroscopy - You mention algorithms such as EKF and ML models being used in high end BMS. - More detail on what kind of algorithms are used in BMS diagnostics? - What kind of algorithms are used in closed loop/multi-stage charging? - Are these distinct algorithms? - It sounds like I'd need to design precision analog voltage and current tracking circuits placed at the UNRBs terminals so I can properly characterize it before and during extraction. - Is that sufficient to serve the role of the battery analyzer, or are there more metrics to consider? - It seems like the battery analyzer subsystem produces initial measurements, and then the programmable load creates artificial test conditions for the battery analyzer subsystem to generate additional contextual data. From there, ADC, and data logger are what provide me the diagnostic data in an intelligible format. - Does this system description cover the bases? How could it be reconfigured, and what might it be missing? Are there any redundancies? - It seems like the main benefit of the EIS is measuring internal resistance of the battery. - Are there are methods for measuring this parameter, and is EIS the best? - Are there other parameters that only EIS can provide? - Is EIS measurement related to the programmable load? #### YouTube Research Notes ##### # BMS (Battery Management System) || DIY or Buy || Properly protecting Li-Ion/Li-Po Battery Packs https://youtu.be/rT-1gvkFj60 - He's got another video where he builds a custom LiPo Battery Bank - BMS are cheap online - Builds a DIY BMS based on Steward Pittaway's Design - See also Collin Hickey or Adam Welsh - Based on the HY2213 - Single Cell LiPo Battery Charger IC - Can get niche components on Ebay - This may require a microscope - This will require SMT soldering - It would be good to have perfboard and a cutting tool on hand - Along with a technique for actually bridging the stuff - Thinking an LCD display like my air quality monitor - Will need much better crimping process too. Too many JST's when just one is awful. - How do you put out a LiPo fire? LiPo Failure modes to be aware of? - Looks like you have to get an additional PCB for every pair of LiPo cells. hmm.... ##### # EBike Battery Pack || DIY or Buy || Electric Bike Conversion (Part 2) https://youtu.be/b2sBhDxmPmA - 18650 Cells seem to be everyone's go-to choice - He's got these little plastic clip things and metal brackets holding the pack together. They look really nice. - Most Li-Ion cells have a nominal of 3.6V and a charging of 4.2V - So Range is 3V-4.2V - You have to stack up quite a few to get to something like 48V/1000W - A good cell is - Samsung INR18650-25R - 2500mAh - Other alternatives?* - "13S2P Lithium Ion Battery Pack" - what does this mean?* - 13 series, 2 parallel? - Two cells in parallel seems common and safe - But if they're not the same voltage current can flow between them - These plastic spacers are interlocking too. Super cool. - 7mm wide x 0.3mm thick / 40A rated Nickel Ribbon - Cut to length and then - kWeld Battery Spot Welder Tool - Powered by LiPo battery, can make welding spots - 100J / 0.3mm Nickel Strip - Adjutable power output for the spot welding - Press the electrodes into the strip about 3mm apart and hit the button - Charging Method: - CCCV - 1.25A at 4.2V (per cell) - Since it's 13S2P - 54.6V and 2.5A are the actual charging conditions - What other charging methods are there?* - Attach 10AWG wire to the terminals - Measure the voltage of each battery pair - Over a long period of time, the cells will decay. - BMS manages this and slows down decay - This setup doesn't seem like it allows for replacing any particular battery cell... - Active diagnostics to a BMS requires a wire to be soldered to every single cell ![[Pasted image 20241029092851.png]] More Info https://www.instructables.com/DIY-EBike-Battery-Pack/ ##### # Build your own portable POWER STATION (1200w, USB-C and MORE!) https://youtu.be/adY-S8AH_Jc - 84 Cell build - 12S7P build - Good practice to measure each cell and match them into close voltage groups - Matters a LOT more when using old or refurbished cells - Worth investing in a charger to get all the cells up to the same voltage before building ![[Pasted image 20241029093905.png]] - The PVC wrapper on the cells obscures the fact that the body shell is the ground terminal. - Scuffing it can introduce shorts - Again, use the plastic spacers - The spacers do seem to have mounting holes for screws, etc. - Nvm he drilled out the holes himself - Smart to use non-conducting nylon bolts though - Very rigid mounting solution - DO NOT SOLDER DIRECTLY TO THE BATTERY TERMINALS - Battery terminals have large thermal mass so the solder joint will suck - And if you get it too hot it'll damage the battery anyway - Lose Lose Situation - Spot Welder + Nicklel Strips Superior - Thicker strips and heavy duty spot welder for high current packs - NO DISTRACTIONS NO MUSIC WHEN WELDING STRIPS ON - Even dropping a nickel strip onto the pack can short the batteries and cause a huge problem/fire - Clever of him to use a PTFE sheet as an insulating, high temp body material. - Not sure if ASA can do that job. - Basically PTFE body panels and Nylon bolts for everything ![[Pasted image 20241029095605.png]] - Average together the weak nylon bolts using an aluminum plate braced against it all - Some M4 Threaded inserts inserted into the aluminum. But wtf am I seeing here? ![[Pasted image 20241029095723.png]] ![[Pasted image 20241029095748.png]] - Looks sturdy now - Aluminum Panels with a Vinyl Wrap is a good way to made something look very polished. - Kapton Tape and Airflow are important - Oak Edgings also look nice ![[Pasted image 20241029095908.png]] - Airflow is important, so it might be a bad idea to put something like this into the understory of breadbox. - Couple of different voltage regulators to provide stock output voltages, and then an adjustable one as well - The whole thing could be run from banana plugs so it can inject directly into the breadboard too. - Smart to include USB charging ports and stuff - This paneling is super clean - Getting aluminum panel+vinyl pilled - High power current connectors - "Dean's Connectors" - Strong enough to power a microwave through an inverter for an hour. Just throw it in your trunk lol. - Pretty heavy though. ![[Pasted image 20241029100646.png]] ![[Pasted image 20241029100755.png]] ![[Pasted image 20241029101111.png]] ##### # Supercapacitor Joule Thief https://youtu.be/jq7cqmDtZDc Quick 5-minute demo of the circuit Question is, can the energy be stored in a supercapacitor and then quantified? Precision of this circuit can vary from 24-96%. Great! Looks like I'll need to overdesign some precision application for this. Horayyy ##### # How Does the Joules Thief ⚡Free Energy Work? https://youtu.be/scH2kFMjetA - It's basically a voltage amplifier - Batteries die as their electrochemical reaction efficiency decreases, resulting in reduced voltage - There are still unreacted chemicals inside, which means we can find a way to extract it - There are several variations of the circuit - Toroidal coil and inductive kickback is the key here. - The toroidal coil has two windings wrapping around in opposite directions. It's more of a transformer - One winding bridges the current limiting resistor to the BJT base - One winding bridges the battery/source to the junction that forks into the BJT Collector and the Load - The two currents/magnetic fields are in opposite directions and cancel eachother out - The stronger current determines the net direction/effect - More current will flow into the collector, since the first path has the current limiting resistor. - The reactive negative voltage from the collector's path then reverses through the transformer and generates a positive voltage along the resistor-base path - This further engages the transistor action - The transistor allowing more current to flow through the CE channel then causes a stronger inductive reaction voltage - Which then flips through the transformer to generate a stronger positive voltage pushing current into the base - This is a positive feedback loop - Once the inductor's magnetic field saturates and stops changing, the reaction voltages dissipate, and current stops flowing into the transistor base, cutting off the CE channel. - Now that the BE path and CE path are both cut off & the inductor is saturated, the inductive kickback process takes place and a voltage spike/burst of energy passes through the load as the inductor's magnetic field collapses - During this time, the inductor also mirrors a countervoltage that prevents current from flowing into the base and reopening the CE channel. - This action is oscillatory and frequency is largely determined by the inductor. ##### # Joule Thief Battery Charger https://youtu.be/I8W20uwtJ3Y Made some improvements - Added a capacitor on xf - zener diode to stabilize base voltage - diode to prevent backflow into bjt - output cap for smoothing/stabilization ![[Pasted image 20241029160936.png]] ##### # All You Ever Wanted To Know About The Joule Thief https://youtu.be/N20gG6bDRlo - Energy capturing - Converting low voltage energy sources into useful output - "A “Joule Thief” is a simple voltage booster circuit. It can increase the voltage of a power source by changing the constant low voltage signal into a series of rapid pulses at a higher voltage." ![[Pasted image 20241029161301.png]] Not actually that useful of a video ##### # How to make an authentic Joule Thief. https://youtu.be/K53beWYdIpc - Oscillator feedback circuit with a transistor - Gonna need to get a battery tester probably - Most single-use battery energy capacity is wasted because electronics require a minimum voltage to turn on. ![[Pasted image 20241029162303.png]] - "Vampire Micro Torch" - Bigclive invented the Joule Thief name lol - Need to hand wind the toroid, which means I need some new parts - Popular BJTs - BC547 - 2N3904 - 2N2222 - One winding goes to the base - One winding goes to the collector - Depends on the core, but it can be around 80-100kHz - There's an element of high voltage ringing that allows it to continue running even after the battery has fallen below VBE/Diode turn-on voltage. - He said it should die around 0.6V, but can run as low as 0.35V - Very interesting effect. Probably one of those 80% of work for the last 20% of output things to get it below 0.35V - You can use a center tap transformer - It has three terminals, so connect the middle tap to the battery's positive terminal Didn't finish this video #### GPT Research Notes ##### @ Overview of Joule Thief Circuit Topology & Function A Joule thief circuit is a simple and efficient boost converter designed to extract the last bit of energy from a power source, typically a low-voltage battery, even when it's almost depleted. Here’s a breakdown of how it works to "drain" a battery: 1. **Components & Basic Setup**: A basic Joule thief circuit consists of a transistor, a small inductor (usually made by winding two coils together on a ferrite core), a resistor, and a low-power LED or similar load. The resistor limits the base current into the transistor, and the inductor stores and releases energy in pulses. 2. **Initial Power**: When power is applied (even at very low voltages like 0.5V), a small current flows through the resistor and into the base of the transistor, turning it on. This allows current to start flowing through the inductor and the transistor’s collector-emitter junction, which causes a rapid buildup of magnetic energy in the inductor. 3. **Inductive Kickback**: As the inductor’s magnetic field builds up, the current through the transistor’s base also increases until it saturates. At this point, the magnetic field collapses suddenly, releasing a “kickback” or spike of voltage. This surge is directed to the load (like an LED), allowing it to operate even if the original battery voltage is below the LED’s forward voltage. 4. **Oscillation & Draining Effect**: This process repeats very quickly, creating a self-oscillating loop where the circuit constantly pulls small amounts of energy from the battery, even when the voltage is below what would normally power the load. This efficient use of remaining energy allows the battery to be "drained" much lower than usual. By leveraging this cyclical storage and release of magnetic energy, a Joule thief circuit can essentially “squeeze” the last joules out of a battery, allowing even near-depleted cells to power low-voltage devices. ##### @ Joule Thief Intermediate Energy Buffer Design To efficiently harness and store energy from low-voltage, intermittent sources, an intermediary power conditioning and buffering stage is essential. Here’s a breakdown of how we can achieve this: ###### 1. **Energy Harvesting Module** - **Purpose**: This module interfaces directly with your low-voltage sources to maximize energy capture, regardless of fluctuations or dips. By stabilizing the input, it ensures that power is conditioned before it reaches the Battery Management System (BMS). - **Recommended Solution**: A specialized *energy harvesting IC* with a Maximum Power Point Tracking (MPPT) algorithm, like Texas Instruments’ **BQ25570**. It’s designed for ultra-low-power energy harvesting from sources as low as 100 mV, perfect for variable solar and kinetic sources. - **Key Features**: - MPPT to maximize energy from intermittent sources. - Built-in power management to enable charging a Li-ion/LiPo battery directly. - Voltage regulation for more stable BMS input. - **Part Number**: TI BQ25570. ###### 2. **Capacitor Bank for Energy Buffering** - **Purpose**: To handle the fluctuations in power output from the sources, especially for short bursts, a capacitor bank can act as a buffer, smoothing the input to the BMS. - **Design Consideration**: Use a capacitor bank with low Equivalent Series Resistance (ESR) to minimize losses. Supercapacitors (e.g., 10 F, 2.7 V) are effective here, as they can handle rapid charge and discharge cycles. - **Recommended Configuration**: Place the capacitor bank after the energy harvesting module and before the BMS input. This buffer ensures the energy from intermittent sources is leveled out before reaching the battery. - **Suggested Part**: A pack of **Maxwell BCAP0010 P270 T01** or similar. ###### 3. **DC-DC Boost Converter for Voltage Regulation** - **Purpose**: Since many of your sources (e.g., solar cells, hand-crank generators) output low and variable voltage, a boost converter is necessary to step this up to the level required by the BMS for efficient charging. - **Recommended Solution**: A *boost converter* with high efficiency at low input voltages, such as the **LTC3105** from Analog Devices. This boost converter is optimized for energy harvesting applications and can output a stable voltage even from input as low as 0.2 V. - **Key Features**: - High efficiency (>90% under optimal conditions). - Adjustable output voltage (up to 5 V, suitable for charging a LiPo battery). - Integrated MPPT to dynamically adjust input power. - **Part Number**: Analog Devices LTC3105. ###### 4. **Joule Thief Variant for Energy Extraction** - **Purpose**: For extracting residual energy from “dead” batteries, a modified Joule Thief circuit will work effectively. A Joule Thief circuit can boost the small remaining voltage to a usable level and transfer this energy into the main power bank. - **Design Adjustments**: Use a toroidal inductor with a high turn ratio to optimize energy transfer from low-voltage batteries. Adding a small capacitor across the battery terminals can help stabilize the extraction. - **Integration**: Feed the output from the Joule Thief circuit into the capacitor bank or directly into the boost converter. This will ensure that even small bursts of residual energy are stored effectively. ###### Suggested Configuration and Flow 1. **Energy Source (Solar Panel/Hand Crank) → Energy Harvesting Module (BQ25570) → Supercapacitor Bank → Boost Converter (LTC3105) → BMS and Battery Bank**. 2. **Dead Battery → Modified Joule Thief → Capacitor Bank/Boost Converter → BMS and Battery Bank**. This setup will allow you to buffer and regulate power from both intermittent sources and the residual energy harvested via the Joule Thief, providing a steady charging flow to your LiPo battery bank. Each component in this intermediary stage conditions the input to ensure stable, efficient charging, even with highly variable or low-power inputs. Let me know if you'd like more specific guidance on circuit design or additional part recommendations! ###### Recommended Parts Here's a list of all the recommended parts: 1. **Energy Harvesting IC** - **Part Number**: Texas Instruments **BQ25570** - **Purpose**: Energy harvesting with MPPT for maximizing energy capture from intermittent sources. 2. **Supercapacitors (Capacitor Bank)** - **Part Number**: Maxwell **BCAP0010 P270 T01** (or similar supercapacitors) - **Purpose**: Acts as a buffer to handle power fluctuations before the BMS input. 3. **DC-DC Boost Converter** - **Part Number**: Analog Devices **LTC3105** - **Purpose**: Boosts low, variable voltage from energy sources to a stable level for charging. 4. **Inductor for Joule Thief Circuit** - **Type**: Toroidal inductor with a high turn ratio (customizable based on desired efficiency and voltage output). - **Purpose**: Used in the modified Joule Thief circuit for boosting residual energy from low-voltage batteries. These components together will enable you to efficiently capture, buffer, and transfer energy from your low-voltage sources into the LiPo battery bank. Let me know if you need details on specific part variants or suppliers! ##### @ Principles and Methodologies for LiPo Charging Certainly! The **Constant Current/Constant Voltage (CCCV)** charging method is widely used for LiPo (Lithium Polymer) cells due to its effectiveness in balancing speed, safety, and longevity. Here’s a breakdown of CCCV charging principles, along with a few alternative paradigms and their unique applications. ###### 1. **CCCV Charging Principles** - **Stage 1: Constant Current (CC) Phase** - In the initial charging phase, the charger applies a constant current to the LiPo cell. This current is usually set to a fraction (often 0.5-1C, where C is the capacity of the battery) to avoid excessive heat generation. - During this phase, the cell’s voltage rises steadily as it accumulates charge. - The constant current phase continues until the cell reaches its maximum voltage (typically around 4.2V per cell for standard LiPo batteries). - **Stage 2: Constant Voltage (CV) Phase** - Once the cell reaches its peak voltage (e.g., 4.2V), the charger switches to a constant voltage mode. Here, the current gradually decreases as the battery’s internal resistance rises with increasing charge. - This phase continues until the charging current drops to a preset minimum threshold (often around 0.05C or less), indicating the cell is nearly fully charged. - At this point, the charging process typically stops to prevent overcharging, which can lead to overheating, cell degradation, or even failure. **Why CCCV for LiPo?** - **Safety**: CCCV helps control the charging process to avoid dangerous conditions like overvoltage, which can lead to thermal runaway. - **Longevity**: By tapering off the current at high charge levels, CCCV minimizes wear on the cell’s structure, extending its useful lifespan. - **Efficiency**: CCCV balances charging speed and cell capacity, maximizing usable charge without overstressing the battery. ###### 2. **Alternative Charging Paradigms** While CCCV is the standard for LiPo cells, there are several alternative methods, each suited to specific scenarios. Some of these include: ###### 2.1 **Pulsed Charging** - **Description**: Pulsed charging delivers bursts of high current separated by short rest periods. During these pauses, the cell's internal chemistry has a moment to "relax," helping to reduce the risk of heat buildup. - **Applications**: Pulsed charging can improve charge acceptance and reduce cell temperature, especially beneficial for fast-charging applications. - **Pros**: Helps with heat management and may slightly extend battery life if managed carefully. - **Cons**: Requires a precise controller to optimize pulse timing, and improperly tuned pulses can lead to cell damage. ###### 2.2 **Inductive or Capacitive Charging** - **Description**: Capacitive or inductive charging is commonly seen in wireless power transfer systems. In these systems, a magnetic or electric field is used to transfer energy to a battery without direct physical connections. - **Applications**: Popular for consumer devices (e.g., smartphones, electric toothbrushes) where contactless charging is desired. - **Pros**: Convenient for devices that need to be charged without connectors. - **Cons**: Typically less efficient than wired CCCV, with limitations on charging rates and more heat generation due to lower efficiency. ###### 2.3 **Trickle Charging** - **Description**: Trickle charging delivers a very low continuous current, just enough to counteract self-discharge. It's commonly used for NiMH and lead-acid batteries but can apply to LiPo in low-power applications. - **Applications**: Useful in maintaining charge in backup or long-term storage scenarios where the battery remains connected but discharges slowly. - **Pros**: Helps maintain charge in idle cells without overcharging. - **Cons**: Not suitable for high-capacity LiPo cells due to the risk of overcharging and cell degradation over time. ###### 2.4 **Multi-Step Charging** - **Description**: Multi-step charging allows dynamic adjustments to the charging current, based on real-time feedback about the cell’s internal resistance, temperature, and state of charge. This approach can involve a mix of CC and CV phases, or even custom profiles tailored to a specific battery chemistry. - **Applications**: Used in high-performance battery management systems, such as those in electric vehicles, where battery longevity and health are critical. - **Pros**: Extends battery life by optimizing each charge phase based on real-time data. - **Cons**: Requires sophisticated control systems and high-quality battery monitoring to avoid damaging the cell. ###### 2.5 **Fast Charging** - **Description**: Fast charging methods use higher-than-standard current rates to shorten charging time. They often employ advanced temperature and voltage management to prevent thermal issues. - **Applications**: Seen in high-demand consumer electronics (e.g., mobile devices) and electric vehicles where time-efficient charging is crucial. - **Pros**: Reduces charging time significantly. - **Cons**: Puts strain on battery cells, potentially reducing lifespan if not carefully managed with proper cooling and current control. ###### Summary The CCCV method remains the gold standard for LiPo due to its balance between charging speed, safety, and battery health. However, depending on your specific needs, integrating elements of alternative methods (like pulsed or multi-step charging) might offer advantages. For example, if you’re aiming to capture energy rapidly from intermittent sources, pulsed or fast charging could optimize your setup, given that you manage cooling and current peaks. For longevity-focused applications, multi-step charging is ideal but requires sophisticated monitoring. Let me know if you’d like to dive into a custom charging solution for your setup! ##### @ Open Loop vs. Closed Loop Charging Paradigms You're absolutely correct in noting that **multi-step/dynamic charging** is generally the most sophisticated closed-loop process among these methods, as it actively monitors and adjusts parameters in real-time based on feedback from the battery. For **CCCV** and **pulsed charging**, let's examine the feedback mechanisms: ###### 1. **CCCV Charging: Open-Loop with Basic Feedback** - CCCV charging is often considered *semi-open loop*. While it does incorporate some feedback from the battery (mainly voltage and current readings), this feedback is typically limited to two main transitions: - **Constant Current to Constant Voltage Transition**: Once the battery voltage reaches the predefined threshold (e.g., 4.2V for LiPo), the charger automatically reduces the current to hold a constant voltage. - **Charge Termination**: The process stops when the current decreases below a certain threshold in the CV phase. - **Feedback Complexity**: CCCV does not dynamically adapt based on the battery’s internal resistance, temperature, or other parameters beyond voltage and current. In other words, it doesn't continuously evaluate the battery’s condition to optimize charging but rather follows a preset “recipe” based on standard LiPo characteristics. - **Closed-Loop Aspects**: Though it uses basic feedback for transitioning stages, CCCV is largely *open-loop* in nature because it lacks continuous, real-time adjustments based on battery condition. ###### 2. **Pulsed Charging: Open-Loop with Limited Feedback** - Pulsed charging can be designed as either open-loop or semi-closed loop, depending on the sophistication of the charger. - In simpler implementations, the charger applies high-current pulses with timed intervals, disregarding the battery’s state. This is fully *open-loop* and risks overheating if not carefully calibrated. - **Advanced Pulsed Chargers**: More advanced designs include temperature monitoring or voltage feedback to control pulse duration, frequency, and intensity, introducing some level of closed-loop control. However, these designs still lack the detailed, real-time adaptability of multi-step charging. - **Feedback Complexity**: Compared to CCCV, even advanced pulsed charging doesn’t analyze real-time changes in internal resistance or dynamically adjust pulse profiles based on real-time data. Instead, it often uses a preset duty cycle or interval control based on initial temperature or voltage. ###### 3. **Multi-Step/Dynamic Charging: Fully Closed-Loop** - **Feedback Integration**: Multi-step charging uses comprehensive, real-time feedback from multiple parameters, including: - Voltage and current readings - Temperature - Internal resistance estimation (through Electrochemical Impedance Spectroscopy in sophisticated systems) - **Dynamic Adaptability**: Multi-step systems continuously adjust the current, voltage, and even charging profile based on the state of charge, battery health, and temperature. This ensures optimal charging tailored to the battery’s exact condition, making it a fully closed-loop system. - **Applications in Complex Systems**: Due to its complexity, dynamic charging is common in electric vehicles and high-performance batteries where precise charge management is critical to maintain long-term health and efficiency. ###### Summary - **CCCV** and **pulsed charging** incorporate basic feedback but operate largely on preset parameters, with limited real-time adaptability. - **Multi-step/dynamic charging** stands out as the only fully closed-loop approach, adjusting continuously based on a rich set of real-time battery data. This real-time adaptability is why multi-step charging is favored for high-value batteries and applications where precise charge management is crucial. Let me know if you'd like to explore ways to implement closed-loop control in your charging setup! ##### @ Differences in Diagnostics & Instrumentation for Rechargeable and Non-Rechargeable Batteries Here’s a breakdown addressing each of these high-level questions in detail. ###### What goes into high-quality battery monitoring & diagnostics? High-quality battery monitoring and diagnostics aim to ensure battery performance, safety, and longevity, and require sophisticated instrumentation and techniques to monitor real-time status, predict battery life, and detect faults. Key elements include: 1. **Voltage Monitoring**: Accurate voltage measurement is foundational for tracking a battery’s state of charge (SoC) and state of health (SoH). High-quality systems often use precise analog-to-digital converters (ADCs) to minimize measurement error and may apply noise filtering techniques to ensure accuracy. 2. **Current Measurement**: Real-time current monitoring helps determine charging/discharging rates and battery efficiency. Hall-effect or shunt-based current sensors with high precision and fast response times are common. Accurate current data is critical for calculating cumulative capacity (mAh) and efficiency. 3. **Temperature Sensing**: Temperature directly impacts battery health and safety, as overheating can lead to thermal runaway. Thermistors, RTDs, or digital temperature sensors close to or integrated within battery packs provide real-time data. High-quality systems include multiple temperature sensors to monitor cell and module temperatures, allowing for prompt intervention if anomalies are detected. 4. **Internal Resistance Measurement**: Internal resistance is an indicator of battery aging. Techniques like Electrochemical Impedance Spectroscopy (EIS) or simpler pulse-resistance methods provide real-time resistance data, allowing early detection of degradation. This requires precision current pulses and complex signal processing. 5. **State of Charge (SoC) and State of Health (SoH) Estimation**: Advanced battery management systems (BMS) use algorithms to estimate SoC and SoH based on voltage, current, temperature, and historical usage data. Algorithms such as Extended Kalman Filtering (EKF) or machine learning models are employed in high-end BMS for accurate, predictive diagnostics. 6. **Cycle Counting and Usage Profiling**: Cycle counting tracks charging/discharging cycles, while profiling usage patterns helps in estimating battery degradation. High-quality systems correlate cycles with temperature and load conditions to refine SoH predictions. 7. **Fault Detection and Protection**: Fault detection uses all the above data to identify conditions like overvoltage, undervoltage, overcurrent, or over-temperature and takes corrective actions, like shutting down power or isolating cells. ###### How are diagnostic practices different for rechargeable and non-rechargeable batteries? The diagnostic focus shifts significantly between rechargeable and non-rechargeable batteries: 1. **Rechargeable Batteries**: - **Lifetime Monitoring**: Diagnostics focus on prolonging battery lifespan and optimizing performance, with a strong emphasis on monitoring internal resistance, SoH, and SoC. - **Cycle Life Tracking**: Rechargeable batteries undergo cyclic stress, so diagnostic systems track charge/discharge cycles and rate-related degradation to predict and maximize usable life. - **Thermal and Voltage Management**: Continuous monitoring of temperature and voltage helps manage the effects of repeated charging and discharging, protecting the battery from unsafe operating conditions. - **Health Algorithms**: Diagnostic algorithms for rechargeable batteries predict aging by analyzing patterns and usage cycles, essential for informing replacement or recalibration decisions. 2. **Non-Rechargeable Batteries**: - **Residual Capacity Estimation**: The main diagnostic goal is estimating remaining energy, given non-rechargeables do not need cycle tracking. Voltage and sometimes internal resistance measurements provide a gauge of residual capacity. - **One-time Use Management**: Since these are single-use batteries, monitoring focuses on evaluating whether they can safely power a device until depletion. - **Internal Resistance**: As non-rechargeable batteries age, internal resistance increases and impacts performance. Diagnostics track this parameter to gauge the battery's viability. - **Disposal Readiness**: Diagnostics assess end-of-life conditions to prevent leakage or discharge hazards, especially important for safe disposal. ###### Instrumentation for Evaluating Used Non-Rechargeable Batteries (UNRBs) Accurate diagnostics of used non-rechargeable batteries requires careful instrumentation to gauge remaining capacity, internal resistance, and viability for energy extraction. Here’s a list of relevant instrumentation: 1. **Battery Analyzer**: - Specialized battery analyzers can measure capacity, internal resistance, and estimated remaining charge. Instruments like the **Cadex C7000 Series Battery Analyzer** are versatile, capable of testing a wide range of battery chemistries and sizes, providing precise measurements of SoC and SoH. 2. **Electrochemical Impedance Spectroscopy (EIS)**: - EIS measures a battery’s internal resistance and response to small voltage perturbations at different frequencies. This helps estimate remaining capacity and overall battery health, especially useful for batteries with high internal resistance due to aging. 3. **Precision Voltage and Current Meters**: - Precision meters, like those from **Keysight or Fluke**, measure voltage and current with high resolution, essential for low-power residual measurements in aged batteries. They also support tests to determine self-discharge rate, an indicator of how much power the battery loses over time. 4. **Programmable DC Load**: - A programmable load, such as the **BK Precision 8600 Series**, lets you simulate various load conditions and observe how the battery responds under load. This test gives a better indication of usable remaining capacity and stability under stress, helping predict energy extraction potential. 5. **Data Logging System**: - To evaluate trends in used battery performance over time, a data logging system (standalone or integrated with your battery analyzers) captures voltage, current, and resistance data at set intervals. This supports historical analysis, helping refine the system's efficacy by identifying patterns in energy extraction success. 6. **Software for Analysis**: - Software that supports curve fitting and model analysis, like **MATLAB** or **LabVIEW**, can analyze collected data to model energy extraction potential based on prior tests, further refining prediction accuracy. ###### Summary To summarize: 1. High-quality battery diagnostics involve voltage, current, temperature, resistance monitoring, SoC/SoH estimation, and fault detection. 2. Rechargeable batteries need continuous monitoring for cyclic degradation and capacity estimation, while non-rechargeable batteries focus on residual capacity and safety checks for disposal. 3. For evaluating UNRBs, tools like battery analyzers, EIS, precision meters, programmable loads, and data loggers are essential for accurately predicting remaining extractable energy, critical for characterizing your system’s performance in reclaiming energy from used batteries. Let me know if you’d like recommendations on specific models or additional configuration details for any of these instruments! ##### @ Long-Term Diagnostics Algorithms vs. Real-Time Charging Algorithms Here’s a breakdown of each question with detailed explanations. ###### What’s an RTD? An **RTD (Resistance Temperature Detector)** is a sensor used to measure temperature by correlating the resistance of the sensor element with temperature. The most common RTDs use platinum (Pt100 or Pt1000 sensors) due to its stable, predictable resistance changes over temperature, making it suitable for precise measurements. **Key Characteristics of RTDs**: - **Accuracy**: RTDs are highly accurate and stable, with linear response curves that make temperature measurement straightforward. - **Range**: They typically operate from -200°C to +600°C. - **Durability**: RTDs are durable and provide consistent measurements over time, which is why they’re popular in battery management systems (BMS) for monitoring cell temperatures. ###### Overview of Electrochemical Impedance Spectroscopy (EIS) **Electrochemical Impedance Spectroscopy (EIS)** is a technique used to characterize a battery’s internal resistance and impedance by applying a small alternating current (AC) signal over a range of frequencies and measuring the battery’s response. **How EIS Works**: - **Frequency Spectrum Analysis**: EIS varies the frequency of an AC signal across a battery or cell and records the resulting voltage and current. By analyzing impedance across frequencies, it detects aspects of internal resistance related to the battery’s chemistry, electrode properties, and electrolyte condition. - **Key Parameters Extracted**: - **Internal Resistance**: EIS provides both the real and imaginary components of impedance, breaking down resistive and capacitive aspects, which correlate with internal resistance and charge transfer resistance. - **State of Health (SoH)**: Because impedance tends to increase with aging and degradation, EIS is a reliable method to evaluate SoH, giving insights into battery lifespan and performance degradation. - **Applications**: EIS is commonly used in laboratory settings and high-end BMS to assess cell quality, aging, and failure modes. ###### Algorithms in BMS Diagnostics High-end BMS diagnostics employ algorithms to assess battery condition, predict remaining useful life, and optimize charging/discharging safely. Here are some commonly used algorithms: 1. **Kalman Filter Variants (e.g., Extended Kalman Filter - EKF)**: - **Purpose**: EKF is widely used for SoC and SoH estimation, as it can handle the nonlinearities of battery characteristics. - **How It Works**: The EKF updates its SoC and SoH predictions based on observed voltage and current, refining its estimates by comparing predicted values with real-time measurements. It’s especially useful for filtering out noise and adjusting predictions based on unexpected deviations. - **Advantages**: Provides robust and adaptive estimations with relatively low computational overhead. 2. **Machine Learning (ML) Models**: - **Purpose**: ML models like neural networks, regression models, or support vector machines (SVM) are used for SoH prediction and fault detection. - **How It Works**: ML algorithms learn from historical data on voltage, current, temperature, and impedance to make predictions about battery life, degradation rates, and fault risks. In practice, these models can account for complex battery behavior patterns that are hard to model with physics-based equations alone. - **Advantages**: ML models can generalize across a wide variety of batteries and adapt to new data, improving prediction accuracy over time. 3. **Coulomb Counting with Correction Factors**: - **Purpose**: Coulomb counting is a technique to estimate SoC by measuring the current flowing into and out of the battery. - **How It Works**: This method calculates SoC by integrating the current over time but typically incorporates correction algorithms to compensate for errors like self-discharge or incomplete charge cycles. - **Advantages**: Simple to implement but works best when combined with other estimation techniques (e.g., EKF) to maintain accuracy. 4. **State of Health Prediction Models**: - These use historical data and cycle count information to predict battery lifespan. Empirical models (e.g., Arrhenius models for temperature impact) and data-driven models can both be used here to project degradation under different conditions. ###### Algorithms in Closed-Loop/Multi-Stage Charging Closed-loop and multi-stage charging algorithms differ from those in diagnostics, as they focus on **real-time charging control** to optimize safety, speed, and efficiency: 1. **Constant Voltage/Current Control (CV/CC)**: - In CCCV charging, simple feedback control algorithms, like **Proportional-Integral (PI)** or **Proportional-Integral-Derivative (PID) controllers**, maintain constant current or voltage by adjusting the output based on battery voltage feedback. - **Closed-Loop Behavior**: This maintains stable current or voltage without overcharging or undercharging, ensuring the battery receives a safe, optimal charge. 2. **Adaptive Algorithms for Temperature and Load Management**: - Algorithms monitor cell temperature and adjust charging current to prevent overheating. Some systems use **temperature-feedback control loops** to throttle charging when high temperatures are detected. - **Real-Time Adaptability**: By adjusting in real time, these algorithms prevent thermal damage and extend battery life. 3. **Dynamic Charging Profiles**: - In high-performance applications, **dynamic profiles** adjust current and voltage based on battery impedance, temperature, and real-time SoC feedback. Advanced algorithms, sometimes incorporating ML models, adapt charging parameters to conditions, balancing between fast charging and battery health. - **Complexity**: These adaptive algorithms are more sophisticated than standard CCCV and require ongoing data on the battery’s response to the charge. ###### Are These Distinct Algorithms? Yes, the algorithms for **BMS diagnostics** and **closed-loop/multi-stage charging** are generally distinct, although there is some overlap in data and feedback mechanisms: 1. **Diagnostic Algorithms** (e.g., EKF, ML models, SoC/SoH estimation) are focused on understanding the battery’s current health, remaining life, and identifying potential issues. These often run in parallel with the BMS, gathering data for long-term battery performance analysis rather than direct charge control. 2. **Charging Algorithms** are more about **real-time control** for the charging process. They utilize closed-loop systems (e.g., PID or dynamic feedback profiles) to adjust current and voltage safely during charging. While these algorithms may access diagnostics data (e.g., SoC or temperature) to make charging safer, they don’t perform the deep diagnostics that predict SoH or degradation. In short, diagnostic algorithms focus on **battery condition assessment** and **predictive insights**, while charging algorithms prioritize **immediate charging safety and efficiency**. Some sophisticated BMS systems do combine elements of both, using diagnostic data to inform charging decisions dynamically, especially in multi-step charging setups.