投稿時間:2021-08-22 01:20:13 RSSフィード2021-08-22 01:00 分まとめ(29件)

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python	Pythonタグが付けられた新着投稿 - Qiita	Python Requestsを使ってmultipart/form-dataをin-memoryで送る方法	https://qiita.com/bgcanary/items/6d81b7813434978362f4	辞書データからバイナリストリームまでの道のりfromioimportBytesIOimportjson元なる辞書datahogehogeJSONとして、Stringに変換stringdatajsondumpsdatautf形式でバイトに変換、bytesdatastringdataencodeutfバイトデータをバイナリストリームに変換binarystreamBytesIObytesdataもちろん、JSON以外にCSVやXMLなどもインメモリで作成し、そのままrequestsでmultipartformdataとして送ることが可能。	2021-08-22 00:16:58
python	Pythonタグが付けられた新着投稿 - Qiita	AtCoder Beginner Contest 215 参戦記	https://qiita.com/c-yan/items/c02a960fc9b41db18fdd		2021-08-22 00:01:31
js	JavaScriptタグが付けられた新着投稿 - Qiita	【React】useRefを用いて値を取得しようとしたらundefinedと言われた。~備忘録~	https://qiita.com/haga2miya/items/32e4c7dd0e88781285bb	備忘録ReactHooksのuseRefを用いて、contenteditableにしたdivタグの値を取得するときに躓いたので備忘録として。	2021-08-22 00:23:32
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	PHP　Mongoコレクション削除	https://teratail.com/questions/355484?rss=all	困っています。	2021-08-22 00:55:26
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	Swift　エラー　Thread 1: "Collection path cannot be empty."の解決方法を教えてください。	https://teratail.com/questions/355483?rss=all	SwiftエラーThreadquotCollectionpathcannotbeemptyquotの解決方法を教えてください。	2021-08-22 00:50:01
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	自作のGoogleHomeアプリで標準の命令を呼び出したい	https://teratail.com/questions/355482?rss=all	自作のGoogleHomeアプリで標準の命令を呼び出したい前提・実現したいことGoogleHomeでYoutubeのおすすめ動画を音声検索し、検索結果の動画をスマートホームで接続している別端末で再生する自作アプリを開発したいと思っています。	2021-08-22 00:47:41
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	スプレッドシートのクエリ関数のエラーについて	https://teratail.com/questions/355481?rss=all	スプレッドシートのクエリ関数のエラーについてシート名「s」の「M列」にある、等の文字列から、文字列の先頭にがつくもののみをシート「s」に抽出しようと、クエリ関数のlike演算子を使用したのですが、エラーでどうしても抽出できません。	2021-08-22 00:45:48
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	iOSアプリ開発におけるライセンスの影響範囲を理解したい	https://teratail.com/questions/355480?rss=all	iOSアプリ開発におけるライセンスの影響範囲を理解したい現在、iOSアプリを開発中なのです。	2021-08-22 00:39:57
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	Railsアプリをデプロイ中、credentials.yml.encの設定が通らない。	https://teratail.com/questions/355479?rss=all	Railsアプリをデプロイ中、credentialsymlencの設定が通らない。	2021-08-22 00:37:46
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	Python pandasで読み込んだcsvのある列から空白を基準に文字を抽出して新たな列に追加したい。	https://teratail.com/questions/355478?rss=all	Pythonpandasで読み込んだcsvのある列から空白を基準に文字を抽出して新たな列に追加したい。	2021-08-22 00:28:16
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	Local by Flywheel にて、通常モードでブラウザからアクセスできない	https://teratail.com/questions/355477?rss=all	LocalbyFlywheelにて、通常モードでブラウザからアクセスできないLocalnbspbynbspFlywheelnbspにて、通常モードでブラウザからアクセスできない実現したいことLocalnbspbynbspFlywheelのローカル環境をSSL化したいです。	2021-08-22 00:27:29
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	laravel8にてAuth::id()でユーザーID を取得できない。	https://teratail.com/questions/355476?rss=all	laravelにてAuthidでユーザーIDを取得できない。	2021-08-22 00:18:13
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	数字の置換ができない	https://teratail.com/questions/355475?rss=all	数字の置換ができない現状のプログラムの結果のをにそれ以外の数字をに変換したいのですが上手くいきません。	2021-08-22 00:09:55
AWS	AWSタグが付けられた新着投稿 - Qiita	The service is unavailable. で EBS ボリュームを変更できないタイミングがある	https://qiita.com/hayao_k/items/445563288fc89072f09d	TheserviceisunavailableでEBSボリュームを変更できないタイミングがあるAmazonEBSボリュームはホスト側のメンテナンスにより変更操作ができないタイミングがあります。	2021-08-22 00:32:13
海外TECH	DEV Community	Updating Node.js to 16+ in Replit	https://dev.to/arnavkr/updating-node-js-to-16-in-replit-1ep0	Updating Node js to in ReplitHey There Welcome to my first post today i ll tell you how can you update your Replit s Nodejs version to so lets get started Many want to do that as to support Discord s latest v as it would only run on Nodejs v or higher But there maybe your own reasons Nobody likes old versions Here s our repl at version x x after this tutorial it will be updated to At first go to your repl or if you don t have any just create one Go to the shell prompt and run the following codenpm init y amp amp npm i save dev node amp amp npm config set prefix pwd node modules node amp amp export PATH pwd node modules node bin PATHAfter running the code you would see the following output And congo your repl s nodejs has been successfully updated to You could further confirm it by running node v in the shell	2021-08-21 15:42:55
海外TECH	DEV Community	8 examples to show Customer Obsession as a Software Engineer	https://dev.to/getworkrecognized/8-examples-to-show-customer-obsession-as-a-software-engineer-9b1	examples to show Customer Obsession as a Software EngineerCustomer Obsession is manifested in many of the career ladders of the top technology companies But why is that and how can you as a Software Engineer show this principle right now at your current job What is Customer Obsession Customer obsession is a principle that describes your effort to make your customer happy It can be applied to almost all positions in a world where you are working on problems that not only you have This goes from end customer facing roles to internal roles where your customer is another employee To make your customer happy there are different methods you can apply to make it work The most important one is to know what your customer wants and for that you have to be able to put yourself into the customer s perspective and try out the work you have been doing from that perspective See where you can improve things and be proactive with your actions to make the customer love your work Who is using Customer Obsession as a Leadership Principle The biggest technology companies are actively using this principle AmazonKlarnaGitHubAnd Many moreA lot of companies have made this principle a core principle of them and that has a reason Within the last to years our software was getting closer and closer to the end customer Everyone has experience with top notch experiences provided by big apps like Instagram Facebook TikTok or Uber to name a few They just work as expected and without any problems Why Because the customer loves them So let us jump into the examples Examples you can do to show customer obsessionPracticing customer obsession is difficult on day to day basis as a software engineer This is because they do not have everyday contact with the customers of the product they create But there are many indirect touchpoints you can have Let us discover them Supporting the customer when neededEver got asked a question by your support or salesperson in the company about a customer problem This is a big opportunity to show customer obsession Try to understand the salesperson or the support person first Listen And ask a lot of questions And also if possible get to the direct words of the customer Once you have gathered enough information you can answer questions quite easily but get the whole picture first In bigger companies you are mostly shielded away from direct customer feedback and your product owner will probably talk to you regarding the customer s problems Make sure that the data backs this up and that this is something the customer wanted Seek to understand the customerIn the example presented before you could see already that you should be able to understand the customer by listening to third parties like someone in the company But now let us go one step further Someone in the company will have calls with customers from time to time Ask them to join from time to time Maybe once per month for an hour will work out But this will be a worthwhile hour you will learn a lot And in these sessions take notes of what the customer wants how they think and how you could affect them with your work Think ahead exceed customer s expectationFeatures and bugs are normally driven by the customer A customer wants something to be done in your company s product or found a mistake blocking their workflow in one way or another The special skill to have now is to think more ahead especially for features The customer requests a feature but the problem might be that the customer wants to achieve a lot more than they requested To solve this you need to think like the customer and think what are the next steps for this feature Is there a relation or can it be made easier For example if you do frontend development it would be a simple idea to count the clicks till a customer will achieve what they wanted Is there a way to reduce the clicks for the customer by prefilling fields in a clever way like they have used it last time or based on other suggestions Or when it is a backend problem you can put extra focus on error messages and guide the customer to a solution or what they should have done instead Most errors are simply describing only the state good errors will give hints what the customer should do instead Put yourself into the customer s shoesAs we have learned in the last examples you will have to get a feeling of how the customer is seeing your product This is difficult If there is any secret of success it lies in the ability to get the other person s point of view and see things from that person s angle as well as from your own Henry FordBut no problem you can learn it Listen to the customers and use your product Write down the smallest things that are problematic for you Wrong colors wrong behavior and whatnot You will get a feeling of what the customer could feel Not all humans and also not all customers are equal Some see one thing as a problem but others look at different problems Try to understand each perspective It will be golden for your whole career Find Problems within your productAs we mentioned before finding problems and barriers in your product is worthwhile From now on simply spend hour with your product every week where you write down annoyances when you are using it Gather these thoughts and present them to your product owner or create tickets for these problems Find data to understand customer satisfaction and loyaltyA problem most companies have with customer obsession is that it is not measured Most companies just have abstract KPIs like revenue or user numbers But what impacts the customer obsession is probably two metrics Customer ChurnCustomer SatisfactionBoth can be measured Customer churn is easy to measure but customer satisfaction is difficult For this you could work together with your product owner to send out surveys to the users of your product every month If response rates are low invite them to an interview People love being interviewed instead of being just a data point But work on getting these metrics and make sure the company is using them for product development Create documentation for your customerEarlier we mentioned that customers ask questions and have demands A problem is mostly that customers are not dumb but cannot find the answer they are looking for This can be a user experience problem but also simply because there is no content So what can you do It s easy write documentation and guides on how your product can be used For example if you get asked a question twice by internal teams write that question down in a FAQ and share it with your team and company peers If it is external even write some documentation for them Most of the time something is better than nothing A big point should be made that documentation is hard to write A good guide can be found here though The documentation system Read through this guide and make it a goal to write down questions in a FAQ and provide documentation Look at competitors how they make the customer happyGood artists copy great artists steal Pablo PicassoWith that quote it becomes clear that it is fine to look at other customers and how they show customer obsession For example just simply look at competitor s documentation and write down why it is better to use them instead of your company s product The same can be applied to everything else like how APIs are designed how many clicks you need to get to the result the customer wanted or when your customer is an internal person how you present them with a solution that should be of high quality So spy on your area of work on how competitors are doing what they might do better and what you can improve for your customers Copy the good parts Understand what customer problems might appear in the futureOutlook is a big part of the higher you want to climb the career ladder Employees that can establish a vision on behalf of the customer are golden Based on KPIs and data from existing customers it should be clear already what is needed in the future Formalizing this data and bringing the company or even team on the right track is important Especially when it is about revenue and how the product could generate more profits for the company Have a look at customer support requests and other data and see if you are observing trends in the whole industry that could be a business opportunity whether it will be a completely new product or just a new feature But with enough data you can present it to your product owner to get validation and lead a project that will be successful But more importantly you will tackle the problems of customers that they mostly do not even recognize yet ConclusionWe hope we could give you some ideas on what you can do as a software engineer to do when you want or need to show more customer obsession After all there are many more examples of how you can show customer obsession If you want to have a free lifetime license feel free to reach out to us with an example of how you showed customer obsession at your job	2021-08-21 15:41:46
海外TECH	DEV Community	✅ Tell Me About A Time Project Took Longer Than Expected | Facebook Behavioral Interview (Jedi) Series 🔥	https://dev.to/theinterviewsage/tell-me-about-a-time-project-took-longer-than-expected-facebook-behavioral-interview-jedi-series-5fna	Tell Me About A Time Project Took Longer Than Expected Facebook Behavioral Interview Jedi Series Before we discuss this question let us recap what the Behavioral Interview Round at Facebook is Behavioral Interview Round is also known as the Jedi Interview round at Facebook It is about you and your history your résumé and your motivation The purpose of this interview is to assess whether the candidate will thrive in Facebook s peer to peer minimal process and unstructured engineering organization For Software Engineers the behavioral interview is actually part behavioral and part coding The coding part is a shorter version of the usual coding interviews and is included to supplement the other two coding interviews to get an additional coding signal Tips amp Tricks to effectively prepare for Behavioral InterviewsKnow yourself Take the time to review your résumé as the interviewer will almost certainly ask about key events in your work history Have concrete examples or anecdotes to support each of the questions Familiarize yourself with Facebook s mission statement and its five core values Be BoldFocus on ImpactMove FastBe OpenBuild Social ValueBe yourself Be open and honest about your successes and failures Be humble and focus on teamwork leadership and mentorship qualities Now let us review how to effectively answer this question Question Tell Me About A Time A Project Took Longer Than ExpectedVideo Explanation with Evaluation Criteria Response Framework Tips amp Tricks Sample Answer Example and a Special Case of Don t Have Any Work Experience Software Engineering projects usually take longer time than planned As a result interviewers often ask the candidates to tell about a time when their project took longer than expected Evaluation Criteria Everyone in their career journey has worked on a project which has taken more time than initially planned By asking this question the interviewer s goal is to assess whether you can adapt and perform in challenging situations or unstructured environments They want to get a handle on how well you can Manage competing priorities Understand the implications of missing deadlines andShift gears when needed They are trying to see if you can distinguish between the urgent and the important Employers want to know your ability to stay calm exercise judgment and act responsibly in such unexpected high pressure situations They are assessing your perseverance to explore the ambiguity and learn new things despite the challenges Interviewers are also evaluating your Communication Time management Problem solving andDecision making skills They are looking to see if your coworkers can rely on you to get the work done Response FrameworkOur advice is to pick a compelling and honest story that can articulate a real life experience where you worked on a project at your workplace which took longer than expected Describe the situation events that occurred and explain how and why the project got delayed from its initial estimation For example it can be any of the following scenarios A few of your colleagues working with you on the project unexpectedly left the team or the company and you were left short staffed to complete it within the current deadline The agreed requirements got modified by the client team in the middle of the quarter Something genuinely urgent comes up like a production issue for which you had to drop everything else Explain to the interviewer how you evaluated and decided your plan of action For example You worked with your manager to re assess the remaining OKRs for the project deprioritize a few optional tasks and create an updated timeline to deliver the necessary features Describe how you were creative and resourceful to get additional help if required either from your own or some other team to deliver the project within the modified deadline Also elaborate on how you communicated about this shift with your manager coworkers and other stakeholders to keep them well informed Finally express how the outcome and the impact were beneficial to the company or team Explain the learnings you took from this challenging situation and how they helped you become a better engineer Tips amp TricksHere are some tips and tricks that will help you effectively prepare this question for the behavioral interview Always remain calm composed and professional Refrain from being negative and avoid blaming your employer coworkers or manager Companies generally do not like to hire people who are always pointing fingers at others Use a compelling story that is honest and believable It is most desirable to describe a real life example to the interviewer to show that you have actually faced such a situation in your career and not just talk about a generic strategy Do not sugarcoat your answer with irrelevant details Spend more time talking about the actions you took to handle the challenging situation Show that you proactively communicated about the shifting deadlines to all the stakeholders to keep them well informed Focus on the business impact that you had on your company or team The biggest way to mess up answering this question is by simply saying that you have never worked on a project at your workplace which took longer than expected Instead explain your strategies for dealing with such situations in your day to day life Prepare the response for this question beforehand as it will be tough to structure your answer on the spot during the interview Do not memorize the answer as it should come naturally and you should sound confident to the interviewer Sample Answer Example Here is Mike He is currently working as a Senior Software Engineer at a major technology company He is interviewing for the role of Staff Software Engineer at Facebook Listen to his response to this question in this YouTube Video Special Case Don t Have Any Work ExperienceIt may be the case that you actually never worked on a project at your workplace which took longer than expected New Grads and entry level software engineers may fall under this category If you are in such a situation Do not end your answer by simply saying no to this question Instead try to use a real experience from your college or day to day life For example The project you were working on as the Graduate Research Assistant got delayed due to new additional requirements This will help the interviewer evaluate you on the following attributes that we mentioned earlier How well you adapt and perform in challenging situations Manage competing priorities Understand the implications of missing deadlines Ability to stay calm exercise judgment and act responsibly Communication skills andTime management skills Preparation MaterialLearn more about the Evaluation Criteria Response Framework Tips amp Tricks and Sample Answers Examples to effectively prepare and answer these top questions asked in the Behavioral Interviews at Facebook Certain special cases are also discussed which are usually faced by the candidates during these interviews ️Detailed Notes on Top Facebook Behavioral Interview Questions Part Cracking the Facebook Behavioral InterviewIf you have not read our first article on Top Facebook Behavioral Interview Questions we recommend reading it by clicking the below link Top Facebook Behavioral Interview Questions Part Facebook Jedi Interview Round The Interview Sage・May ・ min read beginners tutorial programming career Cracking the Facebook System Design InterviewIn case if you have not read our series on Cracking the Facebook System Design Interview we recommend reading it by clicking the below link Top Facebook System Design Interview Questions Part Facebook Pirate Interview Round The Interview Sage・Jan ・ min read beginners tutorial programming career Useful LinksEducative io Unlimited Plan off for first users TryExponent com Membership Limited Time offer Follow for Daily Coding ProblemJoin our membership for exclusive benefits‍Best System Design Interview CourseComplete SWE Interview Course Limited Time offer ‍ ️Behavioral Interview Guide Special Discount Recommended Interview Preparation Book on Amazon ️Buy us a Coffee at BuyMeACoffee com InterviewSageTo stay updated about new posts Subscribe amp Follow Us This article is part of the series on Behavioral Interviews at Facebook So follow us to get notified when our next article in this series is published Thanks for reading ltag user id follow action button background color bdf important color ffafa important border color bdf important The Interview SageFollow Our goal is to create Software Eng Interview tutorials to help you get a job at companies like Facebook Google Apple amp Amazon We will deep dive into System Design Coding amp Behavioral interviews Some images used are from freepik com Freepik pch vector vectorjuice pikisuperstar rawpixel com slidesgo stories Upklyak jcomp macrovector official syarifahbrit redgreystockFull Disclosure amp Disclaimer	2021-08-21 15:24:49
海外TECH	DEV Community	HTML Tags, Attributes and Elements	https://dev.to/codingvarsity/html-tags-attributes-and-elements-3hig	HTML Tags Attributes and ElementsIn this article we will learn about HTML tags attributes and elements If you are just starting with web development and HTML you should be clear about these terms HTML TagsWe have already covered tags in the article What is HTML HyperText Markup Language Tags give special meaning semantics to the text they enclose To annotate a text as the most significant heading we can use the lt h gt tag and annotate text as a paragraph we can use the lt p gt tag lt h gt I am the most significant heading lt h gt lt p gt I am a paragraph lt p gt Opening and closing tagsTags that need to wrap the content have a closing tag For example paragraph lt p gt and headings lt h gt lt h gt lt p gt I am a paragraph lt p gt lt h gt I am a heading lt h gt Tags that do not wrap the content for them the closing tags are not required They are called self closing tags Examples are line break lt br gt and horizontal rule lt hr gt HTML AttributesAttributes are extra information about the tags They are always specified in the opening tag Attributes have a name and value For example for the lt img gt tag we need to specify the source path of the image which can be done using the src attribute Same way for specifying the alternate text we use the alt attribute lt img src media user profile pic jpg alt profile pic gt HTML ElementsThe opening tag closing tag and content together create an HTML Element For example a paragraph element can be a simple lt p gt tag with some content or a nested element with other elements like lt a gt or lt span gt lt p gt I am a paragraph lt p gt lt p gt To read this article visit lt a href link to article gt coding varsity lt a gt lt p gt Tags attributes and elements are the foundation of any HTML document SummaryTags give special meaning to the text they enclose in a document A closing tag is needed if the tag needs to wrap any content Example of closing tags are lt p gt lt h gt etc Attributes are extra information about tags For example the lt img gt tag has src and alt attributes HTML tags along with the content they enclose are called HTML elements	2021-08-21 15:09:50
Apple	AppleInsider - Frontpage News	Weekend Apple Watch Series 6 Sale: Save up to $126 instantly	https://appleinsider.com/articles/21/08/21/weekend-apple-watch-series-6-sale-save-up-to-126-instantly?utm_medium=rss	Weekend Apple Watch Series Sale Save up to instantlyAmazon and B amp H Photo are having a sale on Apple Watch Series models knocking up to off numerous styles Apple Watch deals at AmazonThe Apple Watch deals include discounts on Series GPS Only and GPS Cellular models in your choice of mm or mm Read more	2021-08-21 15:34:54
Apple	AppleInsider - Frontpage News	WhatsApp beta reveals native iPad app is on the way	https://appleinsider.com/articles/21/08/21/whatsapp-beta-reveals-native-ipad-app-is-on-the-way?utm_medium=rss	WhatsApp beta reveals native iPad app is on the wayWhatsApp is working on adding multi device support with a beta of the messaging app revealing it will finally work on an iPad years after the service s launch WhatsApp has always allowed iPhone owners and other smartphone users to use the service but the Facebook owned messenger does not currently have an iPad app available In a beta currently being tested it appears that the situation will soon change A Saturday tweet by WABetainfo reveals that multi device is included in the latest beta The feature currently enables WhatsApp to be used across multiple devices including in a browser and desktop but not with a native WhatsApp app for iPadOS Read more	2021-08-21 15:23:39
Apple	AppleInsider - Frontpage News	Best Deals August 21 - $100 off Radeon RX 6900 XT, $630 UltraWide Monitor	https://appleinsider.com/articles/21/08/21/best-deals-august-21---100-off-radeon-rx-6900-xt-630-ultrawide-monitor?utm_medium=rss	Best Deals August off Radeon RX XT UltraWide MonitorSaturday s best deals include a Scepter inch Ultra Wide monitor off an XFX Radeon RX XT graphics card and a Razer DeathAdder Mini Gaming Mouse Shopping online for the best discounts and deals can be an annoying and challenging task So rather than sifting through miles of advertisements check out this list of sales we ve hand picked just for the AppleInsider audience You ll find more than just Apple products here Each section is organized by product type or brand and can contain anything from furniture to iPhone cases Read more	2021-08-21 15:42:37
海外TECH	Engadget	Hitting the Books: How Tesla engineers solved the problem of exploding EV batteries	https://www.engadget.com/hitting-the-books-power-play-tim-higgins-penguin-randomhouse-153052075.html?src=rss	Hitting the Books How Tesla engineers solved the problem of exploding EV batteriesBetween CEO Elon Musk s often erratic antics strident competition from existing industry titans and a public that is still not fully sold on the idea of traveling via electrical charge Tesla s road to prominence has not been a smooth one But facing a federal investigation into its driver assist systems is far from the biggest roadblock the company has navigated As journalist Tim Higgins explains in his new book Power Play back in the early aughts Tesla s engineering team had to overcome an even tougher challenge keeping the first iterations of its EVs from randomly exploding Knopf Doubleday Penguin RandomhouseFrom the book POWER PLAY Tesla Elon Musk and the Bet of the Century by Tim Higgins published in the US on August by Doubleday an imprint of The Knopf Doubleday Publishing Group a division of Penguin Random House LLC and in the UK on August by WH Allen Copyright by Tim Higgins A panicked letter from LG Chem arrived at Tesla with a dire demand Return its batteries Just as Tesla was proving it could craft a lithium ion battery pack on its own the battery industry was grappling with the danger that cells posed when they were handled incorrectly AC Propulsion had learned this the hard way months earlier in one of an increasing number of incidents that sent shudders through the battery industry En route from Los Angeles to Paris a shipment of AC Propulsion s batteries caught fire as it was being loaded onto a FedEx airplane while it refueled in Memphis triggering an investigation by the National Transportation Safety Board and prompting concerns about how to transport batteries in the future Personal electronics companies such as Apple Inc were recalling devices with lithium ion batteries out of concern they could overheat and catch fire In and Apple recalled more than laptops ーwith batteries made by LG Chem When LG Chem realized it had sold a large number of its batteries to a Silicon Valley startup that planned to use all of them for a single device ーa car as it happened ーits legal department sent a letter demanding the cells be returned The battery maker didn t want to be associated with a potentially fiery experiment Tesla s first CEO Martin Eberhard ignored the request He had little choice His bet that Tesla would be able to find a ready battery supplier was proving harder to cover than expected Without these batteries there might not be a second chance to get more Amid all of the attention on lithium ion batteries Tesla Co Founder CTO JB Straubel thought back to his former house in LA where he and Tesla employee number Gene Berdichevsky celebrated the idea of an electric car by setting cells afire If struck with a hammer they put on quite a show Cars were always in danger of that kind of impact but there was also a more insidious threat He began to wonder what might happen if one of the cells in the tightly packed cluster that would form a car s battery pack got too warm One day in the summer of he and Berdichevsky decided to find out With the office cleared out for the day they went to the parking lot with a brick of cells ーa cluster of batteries glued together They wrapped one of the cells with a wire that would allow them to heat it remotely Then from a safe distance they flicked the heater on The individual cell quickly rose to more than degrees Fahrenheit degrees Celsius causing the battery to flash into a blinding flame as the temperature spiked to degrees then explode altogether sending the remaining skin of the battery into the sky like a rocket Then another cell in the pack caught fire launching into the air Soon all of the cells were on fire Bang Bang Bang Straubel recognized the implications of his amateur pyrotechnics If an incident like the one he cooked up were to happen in the wild it could spell the end for Tesla The next day after they disclosed their experiment to Eberhard they showed him the scorched pavement pitted with holes from the night before Eberhard urged them to be more careful but he couldn t deny that more testing was needed He gathered the team at his rural house on the hills above Silicon Valley for more experiments This time they dug a pit and put a brick of cells in it then covered it with plexiglass They heated one of the cells and again the batteries ignited causing a chain of explosions Straubel had been right this wasn t good They needed outside help to understand exactly what they were dealing with ーthe team needed battery experts Days later a small group of battery consultants were gathered with what at first seemed like a manageable message Yes even the best battery manufacturers produced a random cell that would have a defect causing it to short and catch fire But the odds were remote “It happens really really infrequently one of the consultants said “I mean like between one in a million and one in ten million cells But Tesla planned to put about cells in a single car Sitting near Straubel Berdichevsky pulled out his calculator and computed the likelihood that a cell in one of their cars might catch fire by chance “Guys that s like between one in and one in cars he said And not only would they be churning out cars with defective batteries that if ignited could set off a chain reaction but their cars could be detonating in the garages of the richest of the richーburning down mansions and lighting up local TV news The mood in the room shifted The questions became more urgent Was there anything that could be done to avoid defective cells Nope Random cells were always going to get too hot and spark thermal runaway ーbasically an explosion sparked by overheating Straubel and the team returned to their work deflated The stakes couldn t have been higher for Tesla This wasn t just about solving a hard problem one that threatened to drain limited resources and derail development of the Roadster If they forged a solution that seemed to work only to see Tesla vehicles catch fire in years to come the company would be doomed And it would be a failure not just for Tesla their dreams of the electric car could be set back a generation They could not only cause injury or death they might kill the electric car in the process If they wanted to truly become an automaker they had to face the challenge that GM Ford and others had been dealing with for a hundred years They had to ensure they were putting safe cars on the roadway A solution to thermal runaway could amount to a true breakthrough one that would set Tesla apart from the auto industry for years to come Using lithium ion batteries had seemed like a smart idea one that a number of thinkers had alighted on But figuring out how to use them without turning the car into a ticking time bomb could be their greatest innovation They stopped work on all aspects of the Roadster project and formed a special committee to find a solution The team set up whiteboards listing what they knew and what they needed to learn They began running daily tests They d configure a battery pack with the cells spaced differently to see if there was an ideal distance for containing chain reactions They tried different methods of keeping the batteries cool such as having air flow over them or tubes of liquid brush past them They d take the packs to a pad used by local firefighters for training and ignite one of the cells to better understand what was taking place The danger of the situation was driven home while en route to one of those tests Lyons their recruit from IDEO began to smell smoke coming from the back of his Audi A where he had loaded a pack of test batteries It was a sign that a cell was heating up and approaching thermal runaway He immediately stopped and yanked the batteries out of the car and threw them to the ground before his car could catch fire ーa close call Eventually Straubel began to narrow in on a solution If they couldn t keep a cell from warming maybe they could keep it from reaching the point where it set off a chain reaction Through trial and error the team realized that if they had each cell lined up a few millimeters from its neighbor snaked a tube of liquid between them and dumped a brownie batter like mixture of minerals into the resulting battery pack they could create a system that contained overheating If a defective cell within began to overheat its energy would dissipate to its neighboring cells with no individual cell ever reaching combustibility Where just months earlier they had been struggling to set up a workshop now they were on to something utterly new Straubel was thrilled Now he just needed to figure out how to convince the battery suppliers to trust them Straubel was hearing from Eberhard that the established manufacturers weren t 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