Can you help with laptop repair?! - Page 1
Forum section: electronics / repair

author: rks96
author_rank: Contributor
timestamp: July 22, 2020, 07:28:46 pm
content: A couple of years ago, my sister somehow damaged her laptop (Asus x55vd). When ever AC adapter was plugged in, it shorted out and went in some protection mode - blinking led on AC adapter (short to ground). I did all the basic tests:Test AC power supply with multimeterTest all connections on laptop MBTry different AC adaptor (same voltage and power) at the time I didn't have an adjustable DC power supplyectNothing worked so I stopped trying. Put laptop back together and bought it to local repair shop. A week later I received a message that laptop was damaged beyond repair and they couldn't do anything. Went to another repair shop and same story. After all that laptop was left sitting in the closet.After a couple of years and watching a bunch of Luis Rossman videosI figured it couldn't be that hard to locate busted transistors or shorted caps as long as it wasn't some issue with ICS. For me laptop had no value since repair shops had written it off.At the time I only had 30w soldering iron so I couldn't remove components with more than 2 connections to board so I used heat gun. I started by finding board view of MB and then started to systematically look for transistors that were shorted with multimeter. When I found a shorted transistor I removed it. Plugged AC adaptor back in MB and tested if it still went into protection mode. I also tested removed transistor/mosfet with multimeter diode mode and if everything was ok put it back on using a heat gun. Surprisingly heatgun worked really well. I also disconnected solder jumpers on MB (easy to do with a soldering iron) and repeated AC adaptor test. Using this method I managed to narrow down short location and eventually I found shorted mosfet (4955N RXE37 name PQ8302 in Boardview). Now I needed to find a replacement part. Thankfully I had another damaged laptop (Samsung RF511) on which I looked for mosfet with the same package size and close enough stats comparing datasheets. I found (0803GMT 13756G). Then I replaced shorted mosfet on Asus and now AC adaptor didn't go into protection mode.Asus x55vd have 4GB soldered on MB and you could use another 4GB stick. When trying to boot I could feel with hand that one soldered on the RAM chip got really hot. Well, for me that was pretty much the end, but I remembered from Bordview Googling that Asus x55vd had another version motherboards that didn't have soldered on RAM. Started looking online what was the difference between RAM soldered on MB version and MB version without soldered on RAM. Foundhttps://www.facebook.com/chiplevelexperts/posts/disable-ram-onboard-asus-x55vd/732987710227896/FB post and managed to disable soldered on RAM and removed heating up memory chips. Tried to boot with removable RAM sticks and it BOOTED.Everything worked fine, but the battery didn't charge. Since battery wasn't used for such a long time cells was damaged or gone below 3/2. 5v and BMS disabled battery. I opened battery case and charged it up with DP50V5A using cc+cv hoping that BMS would allow charging if I raised the cell voltage from bellow 3V. Now laptop was running fine from the battery, but still didn't charge. So I put the laptop back together and used it without battery multiple moths. At the same time I ordered a replacement battery (not original).When the replacement battery arrived laptop still didn't charge so the problem still is on the MB. After some time another mosfet (don't remember part number, but PQ8801 in Boardview) burnt out and I replaced it same as before with V1525 FE0KGP. After that laptop is running without any other problems.From what I understand BQ25A, name PU8802 in Boardview is IC responsible for charging. It is also closest to DC connector and battery connector. From its datasheet pin 5 ACOK is high, 2.4 to 3v to start charging. In my case it indeed shows 3v, but the battery doesn't charge. I am also using DP50V5A cv19.1V cc3A to power MB and 0. 003A is pulled without battery (0.006-0.007A with battery attached). I know 19.1 x 3 isn't 90w (original AC adaptor) but it should be fine for testing without system running.BQ25A datasheet is over my head. I would be thankful if you could suggest how to proceed. What points on MB to test with a multimeter - with/without battery - DC power ON/OFF - red probe to ground or black ect. My tools are multimeter, DP50V5A, 30W soldering iron with big ass tip and actual Aliexpress quality hot air soldering station on the way.If you could provide a list with points (Part and pin) from board view and how to test them and I will respond with measurements. I can't promise quick responses since my work station is a kitchen table.http://boardviewer.net/boardview x55vd , BQ25A , and MB picshttps://drive.google.com/drive/folders/1xieP7ywGRVPKq_kht77csyulYBDhxFEM?usp=sharingThanks in advance.PS. I am total noob.

author: rks96
author_rank: Contributor
timestamp: July 22, 2020, 08:13:45 pm
content: On the other note if the repair is a too complicated act, maybe it is possible to use small buck converter connected to the DC in connector (19V) and battery terminal using CC (1A,1.5A) and CV (12.55v/12.6v) accordingly to replace on board charging? I think in this configuration buck converter must be common GND same as laptop MB?! Or do I have to use isolated buck converter?!

author: Rasz
author_rank: Super Contributor
timestamp: July 22, 2020, 08:53:34 pm
content: Quote from: rks96 on July 22, 2020, 07:28:46 pmliar, you brought that crappy laptop back from the dead. Congratulations!Is the battery visible in system at all? Is laptop pretending to charge it (charging led)? Does it maybe try for a split second and stop (charging led blinks once etc)?Check charge current sensing resistor (BQ SRP SRN pins), connect everything like it should charge battery and measure BP pins LODRV HIDRV for activity, check two mosfets between BQ chip and battery connector.

author: de_light
author_rank: Regular Contributor
timestamp: July 23, 2020, 05:47:44 am
content: Hmm. Watching this thread with interest!

author: rks96
author_rank: Contributor
timestamp: July 23, 2020, 11:08:27 am
content: Yes, I can see the battery in the system!When cell voltages were lower than 2.5/3v laptop showed 255 % charge and white X on the battery icon (Windows 10) (at the time I also tried all the battery charger driver reinstalls, remove battery, AC adaptor and RTC battery and hold power button for X seconds ect).When the cell voltage was >3v laptop showed battery percentage as usual and showed "plugged in, not charging".If the battery is connected and then AC adaptor gets connected AC adaptor led starts to shimmer. At this point if the laptop is booted AC adaptor shimmering goes away and when the laptop is powered off shimmering doesn't come back.If AC adaptor is connected first and then the battery is plugged in battery indicator led goes to red (AC adaptor led doesn't shimmer and laptop still can be booted and used as usual. Battery still isn't charging).1)BQ diode mode between SRP SRN pins shows 025 and multimeter is beeping.2)When the original AC adaptor and battery connected and measuring battery terminals there is voltage jump and drop back down. Testing BQ HIDRV no activity LODRV jumps from 12.5 to 12.8v. This corresponds with measurements below of HIDRV PQ8805 and LODRV PQ8804.3)AC adaptor and battery disconnected. Measuring across source and drain with diode mode, source to multimeter -PQ8805 - no shortPQ8804 - no shortPQ8803 - no shortPQ8802 - no shortPQ8801 - short!!! (Already was replaced, but MYB I damaged it?!)4)AC adaptor connected and battery disconnected. Measuring across source and drain with diode mode, source to multimeter -PQ8805 - no shortPQ8804 - no shortPQ8803 - no shortPQ8802 - shortPQ8801 - short!!! (Already was replaced, but MYB I damaged it?!)on battery connector 3.07v5)AC adaptor connected and battery connected (Battery was connected first and then AC adaptor - no red charging led). Measuring across source and drain with diode mode, source to multimeter -DP50V5A set to cv19.1v and cc1a went in to cc mode voltage dropped to 12.78v. PQ8801 starts to heat up!!!!while in cc mode:PQ8805 - no shortPQ8804 - shortPQ8803 - shortPQ8802 - shortPQ8801 - 321 (Already was replaced, but MYB I damaged it?!)While in cc mode laptop also charges battery (don't know if with 19v potential, but measuring cv mode vs cc mode battery terminal voltage starts to go up.5.1)If i rise cc limit somewhere between 4a and 5a DP50V5A goes into cv mode (MYB motherboard has some protection. This also explains why with original adaptor (19v 4.7a) laptop still runs fine - MB protection gets tripped before AC adaptor protection. If cc limit is lowered back to 2/1a cc state doesn't return.After MB protection is tripped (DP50V5A in cv mode):PQ8805 - no shortPQ8804 - shortPQ8803 - shortPQ8802 - shortPQ8801 - short (Already was replaced, but MYB I damaged it?!)6)If AC adaptor is connected first and then Battery (red led on) all measurements are the same as in point 4.

author: aqibi2000
author_rank: Regular Contributor
timestamp: July 23, 2020, 10:46:08 pm
content: You do not perform diode or ohm measurements whilst the circuit is energised. Only voltage measures

author: Rasz
author_rank: Super Contributor
timestamp: July 24, 2020, 12:56:07 am
content: Quote from: aqibi2000 on July 23, 2020, 10:46:08 pmthis! Diode mode is for testing diodes by applying small voltage, you could turn on mosfets by accident and fry something.With circuit turned on use Voltage measurement only.page 28 of BQ datasheet has relevant diagram>AC adaptor led starts to shimmer>PQ8801 - short!!! (Already was replaced, but MYB I damaged it?!)if its blown it could somehow backfeed battery voltage to the supplyLets start with the basics, is the battery low enough for the laptop to want to charge it?)BQ has programmable charging voltage, so it wont charge anything on its own without EC telling it to. I have no idea if there is some software for checking/monitoring this communication availableSomeone measured BQ pins on a working laptop, might be good referencehttps://www.badcaps.net/forum/showpost.php?s=1f43cc3c954e0d3d4bee352e63136d9c&p=489460&postcount=52sadly he didnt measure "battery plugged, not charging" scenario

author: rks96
author_rank: Contributor
timestamp: July 24, 2020, 04:35:04 pm
content: Thanks for diode mode information. I know that diode mode introduces low voltage (example: used for mosfet testing... switching on and off). Looking back possibility that diode mode on powered system can damage something is more than logical. Basic information like this is still very valuable to me. Also proof that I am indeed a noob.No, I didn't charge battery fully with DP50V5A. For reference battery voltage right now is 11. 46V - 3. 82v per cell.I already removed PQ8801 from MB to test and it turned out to be shorted. Right now I don't have anything to put in its place, but I ordered a replacement part. From the board view I googled P0903BEA and in this way found a replacement. Both PQ8801 and PQ8802 are the same, but I can't read anything on PQ8802 package. As a make shift replacement I tried to fit up bigger mosfet 0803GMT but it doesn't switch on (not shorted and works fine when testing with diode mode). Gate threshold voltages are the same. The gate was connected to PC8812 pin 2.Just for testing I disconnected gate and used diode mode (No power to the board) to enable PQ8801 (0803GMT) and MB worked like before. From BQ datasheet page 28 I understand that PQ8801 and PQ8802 is switched by same signal and PQ8802 does still switch on when I manually disconnect gate and trigger PQ8801. So why when gate is connected both mosfets aren't switched on?As from software to talk to BQ from Windows, I don't think there is anything out there. I already searched everything before opening the laptop.Long time ago, before I ordered new battery, I thought that old (original) battery could be damaged or BMS tripped in some safety mode so I tested/read battery BMs using SMBushttp://be2works.com/and CP2112. Free version only allows to read BMS. When I checked it looked like a bunch of flags in BMS was tripped (battery was old and didn't output voltage at terminals even after charging battery with CV/CC). I haven't tried to read the new battery (also uses different BMS chip). I took cells from old battery for other projects. MYB I should read what new battery outputs in SMBus?TNX for link to measurements. For now PQ8801 has been replaced with manually switchable mosfet when should I measure voltages on BQ? Should I at all? MYB wait for replacement P0903BEA?

author: rks96
author_rank: Contributor
timestamp: July 24, 2020, 06:45:25 pm
content: Testing BQ pins with DC power, gate of PQ8801 disconnected and PQ8801 switched on with diode mode:On test pin T4504/rail AC BAT SYS voltage 19.1v. System does boot.All BQ pins with DC power only:1- 19.1v2- 19.1v3- 19.07v4- 24.1v5- 3.0v6- 2.61v7- 0.01v8- 3.31v9- 3.31v10- 0.88v11- 3.09v12- 3.08v13- 3.08v14- GND15- 0v16- 6.04v17- 6.89v18- 3.08v19- 3.08v20- 18.82vThis is almost same as link @Rasz provided!!!!! This gives me hope that BQ is ok.Connected mosfet gate back to MB. When no battery present voltage on gate 0.45-0.5v. At random interval voltage jumps to 1.3,1.4,1.5v,2v.On test pin T4504/rail AC BAT SYS voltage jumps from 3.8 to 8v and in between. The System doesn't boot.All BQ pins with DC power only (gate of PQ8801 connected to MB):1- 3.9 to 4.15v2- same as 13- 0.5v sometimes jumps to 1.5v4- 0.4v5- 0-0.02v6- 2.61v7- 0.01v8- 0,0.2,2.3v jumps around. most of time 0v9- 0.1-0.4 jumps around10- 0.1-0.7v11- 3v12- 3v13- 3v14- GND15- 016- 6v17- 5.9v18- 3v19- 3v20- 18.82vWhat should be the next step?

author: Rasz
author_rank: Super Contributor
timestamp: July 24, 2020, 08:02:53 pm
content: PQ8801 being bad is not connected to not charging at all, together with PQ8802 they just switch power on/off to whole computer when BQ deems it safe (power limits, safety)Is the new battery from ebay by any chance?maybe its bad counterfeit, or incompatible? in ideal world you would test it in another same model laptop

author: rks96
author_rank: Contributor
timestamp: July 24, 2020, 10:47:39 pm
content: Battery is Aliexress special!!! Defenetly not original!!!Only thing I have new is SMBus reading from battery.DesignCapacity: 5200 mAhFullChargeCapacity: 4266 mAhCycleCount: 1Date: 2020.03.08 yyyy.mm.ddDesignVoltage: 11100 mVManufName: AS19DXH3LEDeviceName: K55--52SerialNumber: 002AChargingCurrent: 2500 mAChargingVoltage: 12600 mVDeviceChemistry: LIONTemperature: 24,9 CVoltage: 11478 mVCurrent: 0 mARelativeSOC: 37%AbsoluteSOC: 30%RemainingCapacity: 1563 mAhVCELL4: 0000 mVVCELL3: 3830 mVVCELL2: 3825 mVVCELL1: 3824 mVSpecificationInfo: 0021 HexBattery Status:INIT|DSG|Battery status flags is explained here:http://be2works.com/forum/viewtopic.php?f=3&t=467Also here is an example:https://youtu.be/AyEmM9OLjRs?t=732INIT— 1 = Initialization. The INIT flag is always set in normal operation.DSG— Discharging0 = chip is in charging mode1 = chip is in discharging mode or relaxation mode, or valid chargeNew battery BMS is SH366000AX. Datasheet only in Chinese, but I don't think the problem is in BMS.SMBus is standard for almost all laptop batteries.I could try to read BMS while it is connected to the MB??? BQ operates as a slave. SMBus is pretty much the same as i2c. I think CP2112 also works as a slave when controlled by be2works. The only thing I don't want to do is accidentally triggered situation when DC supply goes in cc. My redneck transistor will desolder.But, on the other hand, maybe I should replace PQ8801 with solder jumper and pump cc in and see what heats up??? The only thing is that in this way I might damage the battery.Also can I desolder FERRITE BEAD row (PL8000) to disconnect and protect the rest of the system in case DC supply CC mode is the way to go???EDIT: Forgot to add BMS pics

author: Rasz
author_rank: Super Contributor
timestamp: July 25, 2020, 03:23:49 am
content: Quote from: rks96 on July 24, 2020, 10:47:39 pmnot optimalQuote from: rks96 on July 24, 2020, 10:47:39 pmbus is standard, but EC(SMC or whatever you call it, ITE chip in this asus) needs to recognize this particular battery as compatibleQuote from: rks96 on July 24, 2020, 10:47:39 pmits a 19V rail, and since you are managing to boot the laptop its not shorted or anythingQuote from: rks96 on July 24, 2020, 10:47:39 pmisnt the PU8000 the one powering EC? and without EC there is no charging anyway

author: rks96
author_rank: Contributor
timestamp: July 25, 2020, 08:17:33 am
content: Quote from: Rasz on July 25, 2020, 03:23:49 amIf BQ doesn't recognize BMS then why it allows laptop to be powered up from the battery?Quote from: Rasz on July 25, 2020, 03:23:49 amBQ Vcc is 18v?! (Straight from DC supply?) I don't understand PCB that well to be 100% sure. (Doesn't matter - AC_BAT_SYS goes to other places on board anyways (I didn't check that before asking) and @Rasz says that rest of the system isn't shorted (looking back this is basic knowledge since system boots and works fine)).So what should I do now?Don't be afraid to suggest something risky that could damage battery/BQ chip ect as long as I can power system back up supplying 12-19v to AC_BAT_SYS. Worst case this could turn in interesting project where I have to use stand alone 3s BMS+buck converter for charging battery and then feeding the power on to AC_BAT_SYS.... Also, I could add an Arduino pro mini as a controller / alarm when battery is too low act.In other words, my final goal isn't (still would like to) fully fixing laptop but having battery mainly as a UPS system for laptop without anything hanging outside original chassis (accidentally unplugging laptop without battery is....).THNX @Rasz for helping.

author: gorge441
author_rank: Contributor
timestamp: July 25, 2020, 10:31:24 am
content: Sounds like your MB has gone. I will suggest you buy a new one.

author: rks96
author_rank: Contributor
timestamp: July 25, 2020, 11:22:45 am
content: Quote from: gorge441 on July 25, 2020, 10:31:24 amIt boots fine and runs fine. Ram now is limited to 4GB (or MYB since now only one channel it can do 8GB single stick.). Also, this project isn't a necessity only doing it for fun and interest.

author: Rasz
author_rank: Super Contributor
timestamp: July 25, 2020, 10:26:11 pm
content: Quote from: rks96 on July 25, 2020, 08:17:33 amBQ is a slave on the bus, doesnt read anything.Quote from: rks96 on July 25, 2020, 08:17:33 amdatasheets says it can be powered with up to 30V.Quote from: rks96 on July 25, 2020, 08:17:33 amThis would be poor formBut I guess you could rig external charging circuit in there, orhttps://hackaday.io/project/5770-smart-battery-smarter-power-packhttps://github.com/abhishek-kakkar/SmartPowerPack/blob/master/powerpack.pyseems initializing BQ is pretty simple:Code:bus.write_word_data(0x09, 0x14, curr)bus.write_word_data(0x09, 0x15, volt)bus.write_word_data(0x09, 0x12, 0x9912)Do you have a logic analyzer? something as basic as $4 EZUSBhttps://www.ebay.com/itm/1pcs-EZ-USB-FX2LP-CY7C68013A-USB-logic-analyzer-core-board-Source-Code/183686874231will be perfect, works withhttps://sigrok.org/.Or probably even arduino if you can program it to sniff i2c.Would be great to sniff SMBUS and check if SMC talks to BQ at all, and if it does what commands it sends.BQ has integrated synchronous buck converter controller driving PQ8804/PQ8805should look familiar:Cant easily test it without osciloscope beyond works/doesnt. Maybe re-test those transistors first.Quote from: gorge441 on July 25, 2020, 10:31:24 amIts always ze germans with this type of comment :-] Dude not every country was rewarded for WW2 by having its economy propped by Marshall Plan to the tune of 1.6K Euro/Monthminimum wageand up to ~7K Euro/Month in unemployment benefits in 2020 ...

author: rks96
author_rank: Contributor
timestamp: July 26, 2020, 11:19:19 am
content: Shamed to admit, but didn't even really knew about logic analyzers and that there was such a cheap option so I don't have one. On the internet I always saw oscilloscope being used for this type of testing (I think) and that's both too expensive for my basic needs and over my knowledge level.I have arduino, esp32 So I usedhttps://create.arduino.cc/projecthub/vincenzo-g/diy-logic-analyzer-f61ee5?ref=tag&ref_id=logic%20analyzer&offset=0to check if BMS and BQ is communicating at all. Here is what i got from it:UNO is limited to 200 samples and data which is logged is at the end of time axis so something might be missing?! If needed I could use the same sketch on esp32 with more memory - more samples)?The battery gets connected to the MB (3 seperate samples):Battery connected, then DC supply:DC supply goes to cc3a mode same as before. Nothing on SMBus.DC supply connected and then the battery:DC supply in CV mode with 1.6A and battery voltage starts to go up. So thebattery is charging and PQ8804/PQ8805 is ok!!!!! This means that in « Reply #4 on: July 23, 2020, 11:08:27 am » point 6 I have wrong information since I used cc limit of 1A, but battery charging needs more. Kind of shot myself in the foot being afraid to melt something. This also shows that the BQ and BMS is communicating OK. Included pic when battery gets connected after DC supply and starts charging (one sample in 2 parts).When I removed the 2nd shorted PQ8801 and tested it all its pins were shorted together, could this somehow feed 19v to gate add damage BQ? On the other hand PQ8802 is ok and uses the same signal from BQ.Right now don't know what to do next. MYB risk, and check, when in cc mode, what heats up besides PQ8801?

author: Rasz
author_rank: Super Contributor
timestamp: July 26, 2020, 02:16:26 pm
content: Great news all around>So I usedhttps://create.arduino.cc/projectseems to be losing bits all over te place, pin8 (clock) is inconsistentat least you can guess the first byte send is 16h = address Bh + 0 R/W bit, while the second command seems to be 17h = address Bh + 1 R/W bitbump the bitrate or try this instead of logic analyzer sketch, should show neat already decoded datahttps://github.com/rricharz/i2c-sniffer-100kBaud-Arduino-Megaorhttps://www.mikrocontroller.net/attachment/378872/i2c-sniffer.c>DC supply goes to cc3a mode>ChargingCurrent: 2500 mAyou might need more than 3A to charge with powered on laptop? one of the things BQ (or SMC) will measure is input voltage drop, and detecting insufficient power supply will stop charging>Right now don't know what to do next. MYB risk, and check, when in cc mode, what heats up besides BQ8801I dont know why BQ8801 would blow at all if BQ8802 doesnt, they are in series and there is nothing else there ... other than PC8812 capacitor, maybe its damaged? Measure PC8812 in resistance mode, obviouslt resistance measurements = everything unplugged.

author: rks96
author_rank: Contributor
timestamp: July 26, 2020, 07:45:23 pm
content: I usedhttps://www.mikrocontroller.net/attachment/378872/i2c-sniffer.cto check SMBus communications because I didn't need to modify any code. Here are the results and how to decode:https://billgrundmann.wordpress.com/tag/i2c-sniffer/file.txt(3.78 kB - downloaded 59 times.)You don't need to waste your time to decode communications. Only if you yourself are interested. As for why battery charges with only 1.6a instead of 2.5 this could be because the battery is in its 1st cycle and BMS is limiting current or when reading battery data incorrect charging current is reported -> battery made in China (don't know if any of this is true just guessing). Also, I am fine if 1.6a is max charging current. BTW battery is 3s2p, each cell Wintonic INR18650 2000mah 3. 7v 7.4Wh 2020.02All previous charging tests were done with the system powered off. BTW without HDD bare MB + CPU and RAM draws around 1.3A when posting+fan spinning.PC8812 black to pin2 red to pin1 1.35-1.45MOhm, probes another way around show open circuit. PC8813 is the same value and type and resistance slowly climbs to infinity as it should be!?

author: Rasz
author_rank: Super Contributor
timestamp: July 26, 2020, 09:36:24 pm
content: Code:12+ 12+ 80+ 98+ 12+ 14+ C4+ 09+ 12+ 15+ 38+ 31+ 16+ 0D+ 17+ 2D+ 00-3 commands :12 9880 some options14 09C4 current, seems to be setting 2.5A assuming 10mohm current sense resistor15 3138 voltage 12.6v>why battery charges with only 1.6a instead of 2.5 this could be because the battery is in its 1st cyclenah, EC is clearly telling BQ to give it 2.5Ampedit: actually measure the charging voltage just to be surecheck resistance of PR8807 PR8810 PR8817, this is feedback loop allowing BQ to measure charging current, I told you to check this in one of the first posts, but I mistakenly did it offhand as talking to another technician and not someone learning stuffresulting in you just buzzing it with diode mode>PC8812 black to pin2 red to pin1 1.35-1.45MOhm, probes another way around show open circuit. PC8813 is the same value and type and resistance slowly climbs to infinity as it should be!?seems fine, measure resistance to ground behind BQ8802, for example resistance of PCE8805. It sure looks like you were just unlucky blowing PQ8801

author: rks96
author_rank: Contributor
timestamp: July 27, 2020, 11:11:24 am
content: LOL I am stupid!!!All this time I have been saying that charging current is 1.6A!!! That is 1.6A @19.1V!!! -> 19.1*1.6=30.5W -> 30.5w/12.6v=2.4A @12.6v!!!This shows that PR8807 PR8810 PR8817 should be fine! The only thing left is why when the battery is already connected and then DC is connected it goes to CC?BTW, there isn't resistance to GND after PQ8802 when supply is in CC mode! Shows open circuit!Right now looks like the only thing left to do is trying to melt next component down the line after PQ8801! The problem is this melting can happen only if the battery is connected!

author: rks96
author_rank: Contributor
timestamp: July 27, 2020, 12:49:55 pm
content: Connected gate of PQ8801 back to MB rised cc limit to max and everything works fine!!!!!! Charging with 1.7 a when DC powersupply is connected after battery.My cc power supply display doesn't react fast enough. Could it be that BQ somehow tests DC powersuply by measuring rated amperage? And why when the battery was connected second everything worked fine to begin with? MYB 2nd PQ8801 shorting out plus using a power supply with lower than original cc limit (technically still enough for charging batteries) resulted in me falling down this rabbit hole?ME FIXING LAPTOP:Will put the laptop back together and test what Windows shows and report back.For now huge THNX to @Rasz for helping and mentoring me.

author: Rasz
author_rank: Super Contributor
timestamp: July 27, 2020, 04:16:23 pm
content: Quote from: rks96 on July 27, 2020, 11:11:24 amQuote from: rks96 on July 27, 2020, 11:11:24 amyou didnt measure resistance with it running, right?why would you phrase it as 'no resistance when in CC mode'?open circuit is a lot of resistance, in fact its close to infiniteits also what we want to seeQuote from: rks96 on July 27, 2020, 12:49:55 pmnot so much a test, as a constant monitoring resistance drop on PR8806. Your lab supply going into CC mode -> dropped voltage -> more amperage -> BQ detects reached limit and shuts down chargingQuote from: rks96 on July 27, 2020, 12:49:55 pmmaybe in this particular order of events power draw is momentarily higher/longerQuote from: rks96 on July 27, 2020, 12:49:55 pmit looks like it wasnt broken to begin with ;-) just CC limited power supply messing with you

author: aqibi2000
author_rank: Regular Contributor
timestamp: July 27, 2020, 04:40:13 pm
content: You can have 3a current during charging and even this high momentarily during inrush initialisation.Set current limit of the bench PSU higher!And be clearer with your comments. You can only measure voltage with the board powered, NOTHING else.

author: rks96
author_rank: Contributor
timestamp: July 30, 2020, 02:11:26 pm
content: Everything is working fine all around!THX again!!

author: aqibi2000
author_rank: Regular Contributor
timestamp: July 31, 2020, 10:55:55 pm
content: What was the final issue

author: Rasz
author_rank: Super Contributor
timestamp: August 01, 2020, 03:33:40 am
content: I see two possibilities- both PQ8801 and PQ8802 were blown- only PQ8802 was initially blown, PQ8801 might of been blown when measuring in diode mode on powered on systemrks96 mentioned in first post replacing "PQ8302", guessing its misspelled PQ8802Problem with PQ8801 is it doesnt matter if its shorted for DC supply operation of the laptop, it will force PQ8802 to also open, something BQ does anyway when it detects the charger.

author: aqibi2000
author_rank: Regular Contributor
timestamp: August 01, 2020, 11:18:06 pm
content: ?

author: JoanNash
author_rank: Newbie
timestamp: September 15, 2020, 02:47:43 pm
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: george.b
author_rank: Frequent Contributor
timestamp: September 15, 2020, 08:46:01 pm
content: Quote from: JoanNash on September 15, 2020, 02:47:43 pmThis is simply hilarious.

author: Refrigerator
author_rank: Super Contributor
timestamp: September 17, 2020, 08:02:30 am
content: Quote from: george.b on September 15, 2020, 08:46:01 pmI like how he came out the woodwork, completely ignoring what has been going on here, and blurted out something as stupid as this. As his very first post on this forum, no less.