[{"data":1,"prerenderedAt":251},["ShallowReactive",2],{"guide-en-jk-bms-weak-cell-log":3,"guides-en":193},{"id":4,"title":5,"body":6,"date":172,"description":173,"extension":174,"keywords":175,"meta":182,"navigation":183,"path":184,"related":185,"seo":189,"stem":190,"updated":191,"__hash__":192},"guides_en\u002Fguides\u002Fjk-bms-weak-cell-log.md","Find a Weak Cell with the JK BMS Log: Trips, Spread and Balance",{"type":7,"value":8,"toc":158},"minimark",[9,19,24,27,40,43,47,50,53,56,59,63,71,89,92,96,104,111,114,126,130,136,141,144,148,151,155],[10,11,12,13,18],"p",{},"When the same cell hits the limit first every time, you probably have a weak cell, and the JK BMS Detail Log shows it. Each trip is logged with the cell number and a snapshot of the highest and lowest cell voltage. Count the trips per cell and look at the gap between cells at the moment of the trip. If you have not exported the log yet, see ",[14,15,17],"a",{"href":16},"\u002Fguides\u002Fjk-bms-detail-log","how to export and read the JK-BMS Detail Log",".",[20,21,23],"h2",{"id":22},"what-a-weak-cell-looks-like-in-the-log","What a weak cell looks like in the log",[10,25,26],{},"Three things point at one cell:",[28,29,30,34,37],"ul",{},[31,32,33],"li",{},"The same cell number appears in most of the trip messages, for example \"Cell 05 over discharge protection\" again and again.",[31,35,36],{},"The max-cell or min-cell column names that cell in the snapshot.",[31,38,39],{},"The spread between the highest and lowest cell is wide when the trip happens.",[10,41,42],{},"Mind the numbering. Cell numbers in the message text start at 1, while the max and min cell columns start at 0, so column value 4 is cell 5 in the message. The snapshot can also lag the event, so the cell in the column does not always match the cell in the message. Trust the spread more than the number in a single row, and look at the pattern over many trips.",[20,44,46],{"id":45},"top-versus-bottom","Top versus bottom",[10,48,49],{},"Where the trips happen tells you what kind of problem it is.",[10,51,52],{},"An over-voltage trip happens at the top, while charging. The cell that rises fastest reaches the limit first and the BMS cuts charging while the rest of the pack is still below it. A cell with lower capacity or higher internal resistance does this. So does a cell that has drifted high because the balancer did not get enough time.",[10,54,55],{},"An under-voltage trip happens at the bottom, while discharging. The cell that drops fastest hits the limit first and the BMS cuts the load while other cells still have charge left.",[10,57,58],{},"A cell that is small or resistive reaches both limits first. It is the first to trip at the top and the first to trip at the bottom. Balance drift looks different. A drifted cell trips at one end, usually the top, and the gap shrinks once the balancer has had several full charges. A capacity mismatch does not go away by balancing, because the cell simply holds less.",[20,60,62],{"id":61},"how-the-analysis-page-decides","How the analysis page decides",[10,64,65,66,70],{},"The ",[14,67,69],{"href":68},"\u002Flogs","log analysis page"," builds a per-cell histogram of trips and compares it with the spread at each trip. It applies a few fixed rules:",[28,72,73,80,83,86],{},[31,74,75,76,18],{},"If the spread at over-voltage trips is tight, see ",[14,77,79],{"href":78},"\u002Fguides\u002Fjk-bms-cell-overcharge-protection-tripping","why cell overcharge protection keeps tripping",[31,81,82],{},"If one cell has at least 80% of the over-voltage trips (3 or more trips) and the median spread is 50 mV or more, it reports a weak or unbalanced cell.",[31,84,85],{},"For under-voltage trips the same test applies: one cell with at least 80% of the trips and a median spread of 50 mV or more gives a weak cell finding. Otherwise the finding says the pack runs empty, which means the whole pack ran down and no single cell is at fault.",[31,87,88],{},"Exports with voltages rounded to 0.1 V are too coarse for a spread. The over-voltage checks are skipped, and every under-voltage case is reported as \"The pack runs empty\", so treat that finding with care on such a file.",[10,90,91],{},"The thresholds are a screening tool. A finding means the pattern fits; check the cell before you replace it.",[20,93,95],{"id":94},"what-to-do","What to do",[10,97,98,99,103],{},"If the trips are at the top and the cell drifts high, work on balancing. Check Start balance voltage and Balance trigger voltage, and make sure the charge reaches the start voltage long enough for the balancer to work. The values and the reasoning are in ",[14,100,102],{"href":101},"\u002Fguides\u002Fjk-bms-balance-settings","JK BMS balance settings",". Then let the pack sit at the top voltage for a few cycles and check the log again. If the spread shrinks, it was drift.",[10,105,106,107,18],{},"If the trips are at the bottom, check the cell itself before touching settings. Look at its capacity against the others, and check the sense wire and connector for that cell. A bad lead or wrong resistance value gives a false reading, see ",[14,108,110],{"href":109},"\u002Fguides\u002Fjk-bms-wire-resistance","JK BMS wire resistance",[10,112,113],{},"If one cell sits 50 mV or more below the rest at rest, after balancing and with good wiring, it is likely a genuinely weaker cell. Replace it or swap in a closely matched one. A mismatched cell keeps limiting the whole pack.",[10,115,116,117,121,122,18],{},"Whatever the cause, give yourself margin. Set SOC-0% and the under-voltage protection in the ",[14,118,120],{"href":119},"\u002F","editor"," so the pack stops before the weakest cell reaches its limit, not at it. Each field is explained in ",[14,123,125],{"href":124},"\u002Fguides\u002Fjk-bms-parameters-explained","JK BMS parameters explained",[20,127,129],{"id":128},"check-it-with-the-log","Check it with the log",[10,131,132,133,135],{},"Open the ",[14,134,69],{"href":68}," and load the Detail Log. The per-cell histogram shows how the trips split between cells, and clicking a bar filters the events to that cell. The episodes table lists each trip with its cells, start, duration, peak and re-arm time. Attach your .jkcfg as well, and the page compares the findings with your configured thresholds. The file stays in your browser.",[137,138,140],"h3",{"id":139},"is-my-cell-bad-or-just-unbalanced","Is my cell bad or just unbalanced?",[10,142,143],{},"Look at the spread and the side. A cell that is high at the top and recovers after a few balanced charges was unbalanced. A cell that stays 50 mV or more below at rest, or trips at both ends, is more likely weak.",[137,145,147],{"id":146},"why-does-the-log-name-a-different-cell-than-the-column","Why does the log name a different cell than the column?",[10,149,150],{},"The message uses numbers from 1 and the columns from 0, and the snapshot can lag the event. Compare many trips, not one row.",[137,152,154],{"id":153},"why-did-the-analysis-say-the-pack-is-empty-and-not-a-weak-cell","Why did the analysis say the pack is empty and not a weak cell?",[10,156,157],{},"No single cell had 80% of the under-voltage trips, or the spread was below 50 mV, or the export has only 0.1 V precision, where every under-voltage case gets this label. Check the cells yourself in that case.",{"title":159,"searchDepth":160,"depth":160,"links":161},"",3,[162,164,165,166,167],{"id":22,"depth":163,"text":23},2,{"id":45,"depth":163,"text":46},{"id":61,"depth":163,"text":62},{"id":94,"depth":163,"text":95},{"id":128,"depth":163,"text":129,"children":168},[169,170,171],{"id":139,"depth":160,"text":140},{"id":146,"depth":160,"text":147},{"id":153,"depth":160,"text":154},"2026-10-02","Find a weak cell in the JK BMS Detail Log: which cell trips first, how wide the spread is at the trip, and whether it is balance drift or a bad cell.","md",[176,177,178,179,180,181],"jk bms weak cell","jk bms one cell always low","jk bms cell imbalance","jk bms cell undervoltage protection","jk bms which cell is bad","jk bms cell voltage difference",{},true,"\u002Fguides\u002Fjk-bms-weak-cell-log",[186,187,188],"jk-bms-balance-settings","jk-bms-detail-log","jk-bms-cell-overcharge-protection-tripping",{"title":5,"description":173},"guides\u002Fjk-bms-weak-cell-log",null,"irfFd_yU84fFEVqX93KOCA0xZxXgi66x_ILR1JkfVg4",[194,199,202,205,208,212,216,220,224,228,231,235,239,243,247,248],{"path":195,"title":196,"description":197,"date":198,"updated":191},"\u002Fguides\u002Fjk-bms-bluetooth-browser","Change JK BMS Settings over Bluetooth in Your Browser","Connect to a JK BMS from Chrome or Edge, read every setting, apply a preset and write it back in a safe order with read-back checks. No JK app needed.","2026-10-04",{"path":101,"title":200,"description":201,"date":172,"updated":198},"JK BMS Balance Settings: Start Voltage, Trigger, Current","JK BMS balance settings explained: start balance voltage, balance trigger voltage, max balance current and the Balancer switch, for LFP, NMC and LTO.",{"path":78,"title":203,"description":204,"date":172,"updated":191},"JK BMS Cell Over Charge Protection Keeps Tripping: Causes and Fix","JK BMS cell over charge protection tripping and releasing every minute? See why a charger set too high causes it, how to tell it from a weak cell, and how to fix it.",{"path":16,"title":206,"description":207,"date":172,"updated":198},"How to export and read the JK-BMS Detail Log","What the JK-BMS Detail Log contains, how to export it from the app, how to read its events and what the log analysis page tells you about trips and faults.",{"path":209,"title":210,"description":211,"date":172,"updated":198},"\u002Fguides\u002Fjk-bms-export-import-settings","Export and Import JK BMS Settings: The .jkcfg File Guide","How to export and import JK BMS settings with the app, what the .jkcfg file contains, why hand edits break it, and how to edit it safely in your browser.",{"path":213,"title":214,"description":215,"date":172,"updated":198},"\u002Fguides\u002Fjk-bms-lifepo4-settings","JK BMS Settings for LiFePO4: 8S and 16S, 280Ah and 314Ah","JK BMS settings for LiFePO4 packs: per-cell voltage, balance, current and temperature values for 8S and 16S with 280Ah and 314Ah cells, in three wear levels.",{"path":217,"title":218,"description":219,"date":172,"updated":191},"\u002Fguides\u002Fjk-bms-log-messages-explained","JK BMS Log Messages Explained: Boot, Time calibration, Protections","What each JK BMS log message means: Boot, Time calibration, APP open charge, protection trips and releases, Discharge On Failed and Unknown Log Code [0].",{"path":221,"title":222,"description":223,"date":172,"updated":198},"\u002Fguides\u002Fjk-bms-nmc-lto-settings","JK BMS Settings for NMC and LTO: Safe Per-Cell Values","JK BMS settings for NMC and LTO packs: per-cell OVP, UVP, balance, temperature and C-rate values in three wear levels, plus how the editor detects chemistry.",{"path":225,"title":226,"description":227,"date":172,"updated":198},"\u002Fguides\u002Fjk-bms-ocp-scp-settings","JK BMS Overcurrent Protection Settings: OCP and SCP Guide","JK BMS overcurrent protection settings explained: charge and discharge OCP limits, delays, recovery times and SCP, with ranges and sizing for inverters.",{"path":124,"title":229,"description":230,"date":172,"updated":198},"JK BMS Parameters Explained: Every Setting by Group","JK BMS parameters explained in one glossary: cell OVP, OVPR, UVP, UVPR, balance, SOC, RCV and RFV, current and temperature limits, with typical LFP ranges.",{"path":232,"title":233,"description":234,"date":172,"updated":198},"\u002Fguides\u002Fjk-bms-password","JK BMS Password: Default Codes, Change and Reset Guide","Your JK BMS password is really two codes: Bluetooth and settings. See factory defaults, how to change them, what to try if one fails, and what to do if lost.",{"path":236,"title":237,"description":238,"date":172,"updated":198},"\u002Fguides\u002Fjk-bms-reboots-power-events","JK BMS Reboots and Charge MOS Off: Reading Power Events in the Log","JK BMS reboots or the charge MOS switched off by itself? Learn to read Boot rows and MOS state in the Detail Log and tell expected restarts from real faults.",{"path":240,"title":241,"description":242,"date":172,"updated":198},"\u002Fguides\u002Fjk-bms-sending-failure","JK BMS Sending failure: Causes and Step-by-Step Fix","JK BMS Sending failure on import? See why the firmware rejects settings (voltage chains, write order, SCP delay) and how to fix it step by step.",{"path":244,"title":245,"description":246,"date":172,"updated":198},"\u002Fguides\u002Fjk-bms-soc-calibration","JK BMS SOC Calibration: Fix SOC Drift, Jumps and Reset","JK BMS SOC calibration explained: why SOC drifts or jumps, what the SOC-100% voltage and SOC-0% voltage do, and how to set them and recalibrate the pack.",{"path":184,"title":5,"description":173,"date":172,"updated":191},{"path":109,"title":249,"description":250,"date":172,"updated":198},"JK BMS Wire Resistance: Fix Abnormal Balance Wire Alarm","JK BMS wire resistance explained: what the abnormal resistance of the balance wire warning means, normal values, common causes and how to fix a bad lead.",1791151315953]