--- title: Fixing A Dead Makita Battery With A 20 Cent Part | daily.dev description: A dead Makita power tool battery that refused to charge was diagnosed and repaired using the open-source PocketOBI tool, which queries the battery's internal... canonical: https://daily.dev/posts/fixing-a-dead-makita-battery-with-a-20-cent-part-mkuefigtf twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Fixing A Dead Makita Battery With A 20 Cent Part | daily.dev og:description: A dead Makita power tool battery that refused to charge was diagnosed and repaired using the open-source PocketOBI tool, which queries the battery's internal... og:url: https://daily.dev/posts/fixing-a-dead-makita-battery-with-a-20-cent-part-mkuefigtf og:image: https://api.daily.dev/og/posts/MkueFiGtF.png og:image:alt: Fixing A Dead Makita Battery With A 20 Cent Part og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Fixing A Dead Makita Battery With A 20 Cent Part **[Hackaday](https://daily.dev/sources/hackaday)** · 2 min read · 0 upvotes · 0 comments ## Summary A dead Makita power tool battery that refused to charge was diagnosed and repaired using the open-source PocketOBI tool, which queries the battery's internal data. One of the battery's NTC thermistors had failed open (infinite resistance), causing the charger to read a false -30°C temperature and refuse to start charging. A second battery showed a faulty 64°C reading. Both were fixed by replacing the failed thermistor — a 20-cent part — with the entire diagnosis-to-repair process taking about ten minutes. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why does my Makita battery charger flash red and run the fan but never start charging? The charger is detecting an out-of-range temperature reading from one of the battery's internal NTC thermistors. A failed thermistor can report a false temperature like -30°C or 64°C, causing the charger to refuse to begin the charge cycle. Replacing the faulty thermistor — typically a 20-cent part — resolves the issue. The PocketOBI tool can query the battery to identify which thermistor is reporting a bad value. _Makers troubleshooting power tool battery failures share fixes like this on daily.dev._ ### What is the PocketOBI tool and what can it do with Makita batteries? PocketOBI is an open-source tool that communicates with Makita battery packs using the reverse-engineered Makita battery protocol, originally documented by the Open Battery Information project. It lets you query internal battery data including thermistor temperature readings, making it possible to pinpoint faults like a failed NTC sensor without specialized equipment. _Hardware hackers working with proprietary battery protocols find relevant teardowns and tools on daily.dev._ ## Similar posts on daily.dev - [Performing An Autopsy On 15 Dead Battle Born LFP Batteries](https://daily.dev/posts/performing-an-autopsy-on-15-dead-battle-born-lfp-batteries-1t7bzyvx2) · Hackaday · 0 upvotes · 0 comments - [Replacing the old battery on rechargeable bike lights](https://daily.dev/posts/replacing-the-old-battery-on-rechargeable-bike-lights-vlq7qzlcz) · Julia Evans · 0 upvotes · 0 comments - [Recline of the machines: Terminator felled by dodgy battery](https://daily.dev/posts/recline-of-the-machines-terminator-felled-by-dodgy-battery-37g6ap7ip) · The Register · 0 upvotes · 0 comments - [Nokia N900 Necromancy](https://daily.dev/posts/nokia-n900-necromancy-8urfeemql) · Hacker News · 4 upvotes · 0 comments - [Battle Born LFP Battery Melts With New Problem](https://daily.dev/posts/battle-born-lfp-battery-melts-with-new-problem-gbfcyrk1f) · Hackaday · 0 upvotes · 0 comments --- Tags: [#hardware](https://daily.dev/tags/hardware), [#reverse-engineering](https://daily.dev/tags/reverse-engineering) [View this post on daily.dev](https://daily.dev/posts/fixing-a-dead-makita-battery-with-a-20-cent-part-mkuefigtf) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Fixing A Dead Makita Battery With A 20 Cent Part","url":"https://daily.dev/posts/fixing-a-dead-makita-battery-with-a-20-cent-part-mkuefigtf","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/fixing-a-dead-makita-battery-with-a-20-cent-part-mkuefigtf"},"datePublished":"2026-08-11T23:25:41.270Z","dateModified":"2026-08-11T23:26:06.737Z","description":"A dead Makita power tool battery that refused to charge was diagnosed and repaired using the open-source PocketOBI tool, which queries the battery's internal...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/9e20c4469d73d3f41f699cbbca294050?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/9e20c4469d73d3f41f699cbbca294050?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Hackaday","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Hackaday","logo":"https://media.daily.dev/image/upload/s--JhDfhy70--/f_auto,q_auto/v1767541814/logos/hackaday","url":"https://daily.dev/sources/hackaday"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/fixing-a-dead-makita-battery-with-a-20-cent-part-mkuefigtf","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"hardware,reverse-engineering","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Hackaday","item":"https://daily.dev/sources/hackaday"},{"@type":"ListItem","position":3,"name":"Fixing A Dead Makita Battery With A 20 Cent Part"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/fixing-a-dead-makita-battery-with-a-20-cent-part-mkuefigtf#faq","mainEntity":[{"@type":"Question","name":"Why does my Makita battery charger flash red and run the fan but never start charging?","acceptedAnswer":{"@type":"Answer","text":"The charger is detecting an out-of-range temperature reading from one of the battery's internal NTC thermistors. A failed thermistor can report a false temperature like -30°C or 64°C, causing the charger to refuse to begin the charge cycle. Replacing the faulty thermistor — typically a 20-cent part — resolves the issue. The PocketOBI tool can query the battery to identify which thermistor is reporting a bad value. Makers troubleshooting power tool battery failures share fixes like this on daily.dev."}},{"@type":"Question","name":"What is the PocketOBI tool and what can it do with Makita batteries?","acceptedAnswer":{"@type":"Answer","text":"PocketOBI is an open-source tool that communicates with Makita battery packs using the reverse-engineered Makita battery protocol, originally documented by the Open Battery Information project. It lets you query internal battery data including thermistor temperature readings, making it possible to pinpoint faults like a failed NTC sensor without specialized equipment. Hardware hackers working with proprietary battery protocols find relevant teardowns and tools on daily.dev."}}]} ```