<center> <img src="https://docs.monadical.com/uploads/425f04a9-7e6f-4613-bb23-87b4f1884293.jpeg" style="width: 330px; border-radius: 50px; border: 3px solid #333; box-shadow: rgba(0, 0, 0, 0.3) 0px 4px 12px;"/> # Building Off-Grid Solar + Battery Power Systems My journey attempting to build a medium-capacity backup power system for my homelab. *Originally published 2023-04-10 on [docs.sweeting.me/s/blog](https://docs.sweeting.me/s/blog) by Nick Sweeting.* </center> --- [TOC] <br/> --- --- <br/> # Project Overview ## Goals <img src="https://docs.monadical.com/uploads/6136d559-25e9-4371-b27e-8172abccbea2.png" style="width: 110px; float: right; margin: 0px 10px; border: 3px solid #a1a1a1; border-radius: 12px; box-shadow: rgba(0, 0, 0, 0.3) 0px 4px 12px;"/> Across 2022-2023 I decided to custom build a battery backup system for my house and van (powered by solar). I wanted my home built solution to beat the specs offered by the [2Kwh Delta Max](https://us.ecoflow.com/products/delta-max-portable-power-station) I bought, which is a magnificent off-the-shelf solution by [EcoFlow](https://us.ecoflow.com) offered for [~$1k USD as of 2023](https://www.ebay.com/itm/144313377136) (~$0.5/wh). I can't beat EcoFlow's economies of scale, but I'm aiming for my final 2Kwh prototype including batteries, inverter, wiring, and enclosure (not including solar panels) to be **buildable for ~$2k USD** (~$1/wh). 💰 *My custom 2Kwh battery cost summary:* > $600 200AH LiFe3O4 + $500 inverter + $100 60A MPPT + $180 case + $600 misc I set out to build a single self-contained, weatherproof [6U rackmount case](https://www.soundtown.com/collections/abs-rack-cases/products/strc-a6ut) to power my entire house (automatically switching between solar, wall power, and backup power, as-needed). I wanted it to have 2kwh of LiFe3O4 batteries built-in, and all the hardware needed to do manual or Wifi-controlled switching, monitoring, and AC/DC conversion mounted on DIN rails within. <br/> #### Buying recommendation <img src="https://docs.monadical.com/uploads/d8aa9fa5-4bc2-4a81-aaaa-d0e42c8d1ce0.png" style="width: 110px; float: right; margin: 0px 10px; border: 3px solid #a1a1a1; border-radius: 12px; box-shadow: rgba(0, 0, 0, 0.3) 0px 4px 12px;"/> If I did this over again I'd probably **just get a [Bluetti `AC300` + `B300`](https://www.bluettipower.com/products/ac300-b300)**, which has 3Kwh of storage capacity ([on Ebay for $2.7k](https://www.ebay.com/itm/385136446784), so it works out to ~$1/wh). ⚖️ For 2x the $/Kwh than EcoFlows, you get a broader range of input/output charging methods, PV priority / combined PV+AC charging, 240v output & grid-tie options via home panel, and higher output power specs. My custom build is about the same per-kwh price as the Bluetti and with similar input/output wattages, but less fit/finish/smarts. However, I only needed 2Kwh, not 3Kwh that the Bluetti offers, so I saved ~$1k (not including the cost of my time to build it, at this point my build is more for learning and fun than saving money 😉). *Also checkout this site where they have kits for DIY batteries at ~$300/kwh: https://jag35.com* <br/> #### Usage goals <br/> 🔢 *What problem am I trying to solve, and what are my needs?* **My power bill in California is too high** ($0.33/kw), and **my power goes down too frequently** (~3x/yr) to be able to reliably host servers at home. By building this system I aim to: - lower my home server's power bill by running+charging everything on solar when available - seamlessly fall back to grid power when the sun fades and my homebuilt battery drains - fall back to my 2kw EcoFlow Delta backup if the grid goes down during a power outage <br/> 🙋‍♀️ *Why not just use my existing 2Kwh EcoFlow? Why go to all this trouble custom building one?* The key thing missing was the ability to have **solar input prioritized over wall power**, with UPS switching between the two. Unfortunately the EcoFlow doesn't allow using solar when wall power is working, it's only designed to kick in as a backup when wall power goes down. All that free solar power is completely discarded except during outages! <small> <br/> *`Solar Priority` is in beta for the Delta 2 and might come to the Max in the future, [see](https://reddit.com/r/Ecoflow_community/comments/zgy2y9/solar_priority_and_other_awesome_features_check/) [these](https://reddit.com/r/Ecoflow_community/comments/127cwy2/delta_2_storing_energy_when_prices_lowprio_solar/) [posts](https://reddit.com/r/Ecoflow_community/comments/11msyvg/faq_about_solar_panels/) for info.* The Bluetti `AC300`, `AC500`, etc. have PV priority and combined PV + AC but cost $1~3k more than EcoFlow. </small> <br/> 💪 *So I added my own auto-switching system I could control...* I built a dual Automatic Transfer Switch (ATS) subsystem mounted on DIN rails that can monitor the AC sources available and auto-switch to my preferred one (auto/manual/or via Wifi app). ``` prefer solar when available: A ----solar inverter-----------------\ use grid when solar is down: B ----AC wall power---ATS[B|C]---ATS[A|BC]--> Home use Delta if A & B are down: C \--EcoFlow Delta--------/ ``` <small>You can also accomplish something similar with an off-the-shelf server [Power Distribution Unit](https://www.amazon.com/Tripp-Lite-Vertical-Rack-Mount-PDUMV40/dp/B000MT4HQM/) (PDU). Look for one that's metered, remote manageable, and supports two or more inputs (most were out of my budget).</small> <br/> #### Can I recoup the cost with power savings? With my new desired setup I get to lower my power bill by about $100/yr per 400w solar panel that I install, and I have 10hr+ of redundant power in case of power outages. With 5x400w panels (~$1750) I can save $500/yr, which takes **~4 years to repay the cost of the panels**, and another **4~5 to repay the cost of the battery+inverter build**. The 2x100AH LiFe3O4 batteries I used claim 3000 cycles before dropping below 80% capacity. Even if it's lower in reality, I think the system can break even before they need replacing. The power security is worth an additional $300/yr to me as it allows me to self-host an expensive NAS + web server for my [internet archiving projects](https://github.com/ArchiveBox/ArchiveBox) that would cost 2x to have in the cloud. <br/> #### Progress so far So far I've built several prototypes with increasingly capable specs. As of April 2023 I have a prototype with 2kwh capacity, 2kw peak AC/DC input/output, and built-in auto-switching between the 3 AC sources available (`A` my solar, `B` the grid, and `C` my EcoFlow Delta Max). <img src="https://docs.monadical.com/uploads/a8fa96ec-7274-4c3a-88b2-1c2cf5919173.jpeg" style="max-width: 254px"/><img src="https://docs.monadical.com/uploads/60d461a4-30b6-4af9-84a6-71404f926df1.jpeg" style="max-width: 451px"/> <br/> --- <br/> ## Specs <img src="https://docs.monadical.com/uploads/464a52b2-7a80-436a-952c-dd21bf950835.png" style="width: 190px; float: right; margin: 0px 10px; border: 3px solid #a1a1a1; border-radius: 12px; box-shadow: rgba(0, 0, 0, 0.3) 0px 4px 12px;"/> I'm designing in remote Wifi monitoring + switching for all the DC/AC inputs/outputs (volts, amps, watts, PF, kwh, ºC, etc.). The brains are a LilyGo T-Relay ESP32+Wifi ([$16](https://www.lilygo.cc/products/t-relay-5v-8-channel-relay)), metering is via DROK AC and DC Hall-effect energy meters (4x[$31](https://www.amazon.com/Voltage-DROK-Battery-Monitor-Display/dp/B07B4CWKRJ?th=1)), and switching is via 12v250a automotive relays (6x[$15](https://www.amazon.com/IRHAPSODY-Continuous-Terminals-Automotive-Electrical/dp/B08F28SKX1/)) + DIN breakers (10x[$11](https://www.amazon.com/12V-110V-Miniature-Protector-Magnetic-Disconnect/dp/B09H4Y8QGY/)). 💁‍♂️ *I prefer [hall-effect power meters](https://www.amazon.com/Voltage-DROK-Battery-Monitor-Display/dp/B07B4CWKRJ?th=1) because they can go around my existing 1/0 AWG wiring and don't require splicing in shunts!* <br/> :::info Wiring diagram symbol key: ``` --(-- XT-60 connector for DC 0~100v 1~40a ᠁᠁> wire continued in another diagram 〰️〰️〰️ 12 AWG copper wires for AC 110v 0~20a ----- 6 AWG copper wire for DC 0~100v 1~50a ===== 0 AWG copper wire / busbar DC 0~12v 100~250a 📡 RELAY: 12v250a Wifi-switchable heavy duty relay 🎬 BREAKER: 12v50a / 110v16a DIN rail AC / DC current overload breaker 🧲 BREAKER: 12v200a large solenoid DC low-current cutoff breaker (automotive) 🔋 BATTERY: 200AH LiFe3O4 12v 2p 2x100AH 🔌 PLUG: connection to the external world ⏲️ METER: DROK AC or DC combo voltage/current/power/energy (0~300V 0~200A) 📦 DEVICE: ATX PSU, MPPT, INVERTER, ATS, BOOSTER ``` ::: <br/> #### AC Input Specs *2x `🔌 AC 110v20a` inputs, 20a total max (`2.2kw`)* ``` /〰️> 📦ATX PSU 960w =)=> 12v80a DC input ᠁> / 110v20a AC from grid 🔌〰️〰️⏲️〰️📡〰️🎬〰️〰️〰️〰️〰️〰️〰️〰️〰️〰️ AC bypass to ATS[B|C] ᠁> 110v20a AC from EcoFlow 🔌〰️〰️⏲️〰️📡〰️🎬〰️〰️〰️〰️〰️〰️〰️〰️〰️〰️ AC bypass to ATS[B|C] ᠁> ``` #### DC Input Specs *3x `🔌 DC 12-100v` inputs, 200a total max (`2.4kw`)* ``` 12v80a DC from ATX PSU ᠁==========)=⏲️=📡=🎬========᠁ 100a DC input breaker ᠁> 100v60a DC from solar 🔌- 📦MPPT =)=⏲️=📡=🎬==/ ⑊ 12v40a DC from BOOSTER 🔌----------)-⏲️-📡-🎬-/ ⑊ 12v40a DC from van/aux 🔌----------)-⏲️-📡-🎬/ ⑊==᠁᠁ 200a DC bypass ᠁> ``` <small>(My batteries max out at 100A charging, extra input power goes via bypass breaker straight to the outputs)</small> <br/> #### Storage + Conversion Specs ``` ᜶=⏲️=📡=🎬=> 🔋:[100AH BATTERY A] ‖ /=======\ ᠁==> 🧲 100a DC input breaker ==‖ ‖=======> 🧲 200a DC output breaker ===᠁> \=======/ ‖ ‖ ‖ ⑊=⏲️=📡=🎬=> 🔋:[100AH BATTERY B] ᜶ ‖ ‖ ᠁====> 200a DC bypass =======⏲️=📡=> 🧲 200a DC bypass breaker ==============᜶ ``` <br/> #### DC Output Specs *3x `🔌 DC 12v40a` outputs, 120a max (`1.4kw`)* ``` ᠁ 200a DC bypass breaker =\ ‖ ᠁ 200a output breaker ᠁᠁========⏲️=📡=🎬=======᠁> to inverter 12v200a DC out ᠁> \--⏲️-📡-🎬-----------------)--> 12v40a DC out -🔌 \-⏲️-📡-🎬-----------------)--> 12v40a DC out -🔌 \⏲️-📡-🎬--> 📦 BOOSTER --)--> 1-36v40a DC out -🔌 ``` #### AC Output Specs *2x `🔌 AC 110v20a` outputs, 20a max (`2kw`)* ``` 12v200a DC from output breaker ᠁=> 📦 INVERTER 〰️⏲️〰️📡〰️🎬〰️\ | 110v20a AC bypass from grid ᠁〰️⏲️〰️📡〰️🎬〰️\ 📦ATS[A|BC] 〰️>110v20a AC 〰️🔌 📦ATS[B|C] 〰️〰️〰️〰️〰️〰️/ \ 110v20a AC bypass from EcoFlow ᠁〰️⏲️〰️📡〰️🎬〰️ 〰️/ \〰️>UPS AC 〰️🔌 ``` <small>Auto Transfer Switch (ATS) priority order: `A. Solar Inverter`, `B. Grid power`, `C. EcoFlow fallback power`</small> <br/> --- <br/> ## Lessons Learned Going into this I knew my first prototype would be over-budget, over-deadline, and under-performing but I hoped to work toward being able to build repeatable, rugged power systems for hard environments like Burning Man or moto-camping. Of course this ended up being the case, I massively exceeded my expected budget within the first month of building prototype v1, but I decided to continue building and optimize for lower cost later. Now that I'm nearing Prototype v3, I fixed many of the rough edges in the design and will start optimizing for cost, repairability, and ease-of-assembly. <br/> **So far this project has taught me some valuable lessons:** <br/> #### How to build weatherproof, modular, nestable enclosure systems for electronics and gear <center> <i>These enclosure systems nest nicely from van-size down to micro component size...</i><br/> <img src="https://docs.monadical.com/uploads/41f228ee-b7cd-4f78-bba9-b59a844b3c0b.png" style="width: 100px; margin: 10px; border-radius: 5px; border: 2px solid #1a1a1a; box-shadow: rgba(0, 0, 0, 0.1) 0px 4px 12px;"/> ➡️ <img src="https://docs.monadical.com/uploads/7a55978b-df5f-411b-9407-258ae66da528.png" style="width: 100px; margin: 10px; border-radius: 5px; border: 2px solid #1a1a1a; box-shadow: rgba(0, 0, 0, 0.1) 0px 4px 12px;"/> ➡️ <img src="https://docs.monadical.com/uploads/51405c91-299e-48f8-b617-86692b75493c.png" style="width: 100px; margin: 10px; border-radius: 5px; border: 2px solid #1a1a1a; box-shadow: rgba(0, 0, 0, 0.1) 0px 4px 12px;"/> ➡️ <img src="https://docs.monadical.com/uploads/93f246e6-52d7-4d9d-8ffb-c66d6284f00f.png" style="width: 100px; margin: 10px; border-radius: 5px; border: 2px solid #1a1a1a; box-shadow: rgba(0, 0, 0, 0.1) 0px 4px 12px;"/> ➡️ <img src="https://docs.monadical.com/uploads/3b9084a7-1d58-4f44-9dda-e813abd1f76a.png" style="width: 100px; margin: 10px; border-radius: 5px; border: 2px solid #1a1a1a; box-shadow: rgba(0, 0, 0, 0.1) 0px 4px 12px;"/><br/> <small><pre><a href="https://www.amazon.com/48-22-8480-Milwaukee-Packout-Racking-Compatible/dp/B0BNNDPFDD/ref=sr_1_7?crid=JDM7WBJN4247&keywords=e-track+shelf+kit&qid=1686349837&sprefix=e-track+shelf+ki%2Caps%2C164&sr=8-7">E-Track -> Milwaukee Packout</a> > <a href="https://www.amazon.com/HQYing-Mounting-Bracket-Alumnium-Oxidation/dp/B0BNBJCD4T">Rack mount cases -> DIN Rails</a> > <a href="https://www.printables.com/model/302052">Gridfinity</a> </pre></small> </center> - [E/X-track](https://cargosmartllc.com/collections/x-track-and-e-track) for large-scale wall or floor-mounting (in vehicles + workshops) - [Milwaukee Packout](https://blog.acmetools.com/milwaukee-packout-storage-system/) for mid-scale shelf mounting / rolling luggage mounting - [Server rackmount cases](https://www.soundtown.com/collections/abs-rack-cases/products/strc-a6ut) for vertical mounting rails in ruggedized rollable ABS cases - [AkroMils bins](https://akro-mils.com/Products/Types/Plastic-Storage-Containers/AkroBins) For bins of various sizes to hold parts, mount on pegboard, and load packouts - [DIN rails](https://en.wikipedia.org/wiki/DIN_rail?) for horizontal mounting between rack mount rails inside rollable ABS cases - [Gridfinity](https://gridfinity.xyz/catalog) for flat surface mounting within Milwaukee Packout / rack mount drawers - <small>[LEGO](https://thangs.com/designer/Link%20The%20Cat/3d-model/Gridfinity%20Lego%20Minifig%20Stand-556997) for assorted small component mounting within gridfinity plates or small enclosures</small> <small><code>* someone needs to build a Milwauee Packout compatible 19" Rackmount case, <a href="https://www.soundtown.com/collections/abs-rack-cases/products/strc-a6ut">Soundtown</a> != Milwaukee</code></small> <small>Alternatives: <a href="https://www.mysortimo.us/en_US/products/container-boxxes">Sortimo Boxxes</a>, <a href="https://toolguyd.com/bosch-l-boxx-tool-storage-system-review/">Bosch L-Boxx</a>, <a href="https://toolguyd.com/dewalt-tstak-tool-boxes/">DeWalt Tstak</a>, <a href="https://www.festoolusa.com/products/systainer,-sortainer-and-systainer-port/systainer">Festool Systainer</a>, <a href="https://justagirlandherblog.com/best-tool-storage-systems/">and more...</a></small> <br/> #### How to do modular power monitoring and switching for 0~240V 0~250A AC & DC - Use ESP32 + LoRA microcontroller for monitoring and control hubs - Use DROK hall effect meters for 0-200A AC or DC power/voltage/current/energy monitoring - Use 250A 12v DC continuous duty automotive relays for switching - Use Etekcity smart outlets for simple Wifi+app AC monitoring and switching #### How to accomplish redundancy and graceful degradation - Use automatic AC & DC transfer switches to switch between multiple input sources for control circuity - Use indoor hydroponics AC power controllers for temperature, humidity, timed AC controllers - always add bypass breakers that allows you to bypass your whole system during maintenance to isolate components without taking the outputs offline <br/> --- <br/> ## Parts List (links are direct/non-affiliate Amazon links, I don't get any commision/referral benefits) #### Batteries and microcontrollers - 2x [100AH 12v ADCBATT LiFe3O4 Batteries](https://www.amazon.com/gp/product/B09NXF1GZ7/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - 1x [ESP32 + LoRa microcontroller board by MakerFocus](https://www.amazon.com/dp/B076MSLFC9?psc=1&ref=ppx_yo2ov_dt_b_product_details) #### Enclosure and mounting hardware - 1x [SoundTown 6U ABS Rack Mount case](https://www.amazon.com/dp/B07XQ2KH1V?ref=ppx_yo2ov_dt_b_product_details&th=1) ([STRC-A6UT](https://www.soundtown.com/collections/abs-rack-cases/products/strc-a6ut)) as enclosure - 6x [1U HQYing Rack mount to DIN rail adapters w/ 19" DIN rails](https://www.amazon.com/dp/B0BNBJCD4T?psc=1&ref=ppx_yo2ov_dt_b_product_details) - 6x Custom 3D printed enclosures + DIN rail mounts for power meters and relays #### General connectors, wiring, breakers/relays, and switches - 6x [40A DC XT-60 male/female connectors](https://www.amazon.com/dp/B08NHB86GY?ref=ppx_yo2ov_dt_b_product_details&th=1) - 16ft [2~12 AWG Oxygen Free Copper wiring w/ silicone insulation](https://www.amazon.com/gp/product/B01MUC6U58/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - 2x [200A copper bus bars](https://www.amazon.com/dp/B07NW7WPBK?psc=1&ref=ppx_yo2ov_dt_b_product_details) - 6x [50A DC 12v DIN rail circuit breakers](https://www.amazon.com/gp/product/B09H4Y8QGY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - 6x [200A DC 12v circuit breakers](https://www.amazon.com/gp/product/B09QSVHFNV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - 4x [40A 221 Series Wago Connectors](https://www.amazon.com/gp/product/B0BKR2SR7H/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - 10x [60A DIN rail wiring terminal blocks](https://www.amazon.com/gp/product/B07TN1S3KQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) #### DC Input/Output Monitoring + Switching Subsystem - 1x [60W 6A XT-60 1-4s 12v Battery Balance charger](https://www.amazon.com/dp/B08F7C1T2T?psc=1&ref=ppx_yo2ov_dt_b_product_details) - 1x [60A PowMr MPPT Solar Charge Controller](https://www.amazon.com/gp/product/B08TWK76X4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - 3x [200A DROK DC Hall effect current sensors](https://www.amazon.com/dp/B07B4CWKRJ?ref=ppx_yo2ov_dt_b_product_details&th=1) - 1x [10A 12v DC auto power switch module](https://www.amazon.com/dp/B07RS48WTH?psc=1&ref=ppx_yo2ov_dt_b_product_details) - 3x [50A DC 12v DIN rail circuit breakers](https://www.amazon.com/gp/product/B09H4Y8QGY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - 1x [200A DC 12v circuit breakers](https://www.amazon.com/gp/product/B09QSVHFNV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - 1x [800W DC boost converter power supply](https://www.amazon.com/dp/B098SVD2B8?psc=1&ref=ppx_yo2ov_dt_b_product_details) - 2x [DORHEA 12v DC boost/buck converters](https://www.amazon.com/dp/B09PND5CJT?ref=ppx_yo2ov_dt_b_product_details&th=1) - 4x [250A 12v DC continuous duty relays](https://www.amazon.com/gp/product/B08F2G1J9D/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1) #### AC Input/Output Monitoring + Switching Subsystem - 3x [2P 100A AC Dual Automatic Transfer switches](https://www.amazon.com/dp/B09PN7CMKM?ref=ppx_yo2ov_dt_b_product_details&th=1) - 3x [DROK 100A AC hall effect sensors](https://www.amazon.com/dp/B0BR75M7W1?ref=ppx_yo2ov_dt_b_product_details&th=1) - 2x [Atorch Wifi AC power usage meters](https://www.amazon.com/dp/B0BGSYJQK6?psc=1&ref=ppx_yo2ov_dt_b_product_details) - 1x [AC Single Phase DIN rail hall effect current meter](https://www.amazon.com/dp/B094F98PYF?ref=ppx_yo2ov_dt_b_product_details&th=1) - 1x [900W 1500VA CyberPower AVR UPS](https://www.amazon.com/dp/B0BCMLLSHL?ref=ppx_yo2ov_dt_b_product_details&th=1) - 1x [KETOTEK digital thermostat AC temperature controller](https://www.amazon.com/dp/B0957NYW37?psc=1&ref=ppx_yo2ov_dt_b_product_details) <br/> --- --- <br/> # Build Photos <br/> ## Design & Planning     --- ## Prep Work - capacity testing existing 12v lead acid batteries - aquiring new 100AH LiFe3O4 batteries - load testing and verifying various batteries, breakers, relays, and interconnect approaches    --- ## Version 0: Prior attempts From 2018 - 2021 I succesfully used two UPSs hooked up to external lead acid battery banks. (needed to power a Unifi networking system and a Dell r610 rackserver during Quebec ice rain power outages ⛈️) - 1x Raspberry Pi for monitoring connected to the UPS by USB - 6x 12v 22AH Lead Acid batteries for mobility scooters - 1x 300w UPS - 1x 600w UPS   --- ## Version 1: Prototyping I built this one in late 2022, a first pass approach with my new 2x 100AH batteries using simple relays and power meters. - 1x 17gal black & yellow bin as the enclosure (inspired by Burning Man packing) - 2x 100AH Lithium Iron Phosphate batteries - 2x copper stock bus bars for main DC power rails - 5x 100~200A 12v DC Automotive circuit breakers for control - 2x 200A DC shunt-based Current / Energy meter for DC input/ouputs - 6x XT-60 connectors for DC in and output connections - 6x Wago 221 connectors for quick connect/disconnect wiring    --- ## Version 1: Finished Prototype Succesfully handles 100A DC input and 200A DC output with simple relays and two shunt-based power meters. Driven by 60A solar MPPT + 400W panel. Outputs 200A to a 2000w inverter which goes through an ATS to power the 1500w server UPS and ~400w of misc garage loads. *Limitations:* Offers no remote monitoring/switching and has low ruggedness (40A XT-60 plugs)  --- ## Subsystem: Automatic Transfer Switch Automatically switches between 2~4 available AC power sources depending on which are available, favoring them in a pre-set order. - 3x DIN rails for mounting / organization - 3x 16A AC inputs via spliced extension cords - 3x 16A AC circuit breakers for input switching - 2x 100A AC Automatic transfer switches to switch A/B -> AB/C -> output - 1x 100A AC hall-effect sensor for output monitoring - 1x Wago 221 connector for ground/neutral bus wiring      --- ## Version 2: Prototyping Goals: improvement by moving version 1 inside a 6U rackmount case, with DIN rails and 3d printed enclosures + acryllic backing to mount everything. I think remote switching with 12v 250A relays everywhere is too much work and too bulky, but I can still shoot for remote monitoring by tapping onto the hall effect sensors used by the DROK energy meters. See parts list at the top ^^^            --- ## Version 2: Finished Prototype       ### Specs - 4x 100AH 12v LiFePO4 Batteries (400AH total ~4.8kwh) - 4x 250A 12v Relays - 2x 200A Copper Bus Bars - 20ft of 1/0 AWG Copper Wiring ($$$) - 12v 4-channel remote relay box - 3x Voltimeters --- --- # Side Quests ## Side Quest 1: Setting up my garage workshop space       ## Side Quest 2: Fixing a failed Eaton UPS An [`Eaton 5SC1500 1500VA UPS`](https://www.eaton.com/us/en-us/skuPage.5SC1500.html) I got on Ebay for this project blew a trace out near one of the bridge rectifiers on the board when I first tried turning it on with 3S 36v of LiFe3O4 batteries. Perhaps because the batteries were slightly overcharged to 38v total? I attempted to fix it by soldering around the blown trace and replacing the bridge rectifier (2W10 2A 1000V Diode Bridge Rectifier marked `2W10G 348C` in the `REC2` slot, near `JP01`, `JP02`). Unfortunately the UPS continues to beep and show `bad battery` and `internal fault` error codes after the repair, not sure if it's an incompatibility with my batteries or another issue with the board (maybe why it blew the trace in the first place). I'm shelving this repair for now and using a cheaper CyberPower UPS until I have time to revisit this.     --- # Further Reading - https://www.instructables.com/Grid-Tie-Inverter-V2/ - https://openinverter.org/wiki/Main_Page