Author Topic: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack  (Read 105046 times)

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Online lern01

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #150 on: May 16, 2022, 08:49:52 am »
Thank you very much for your hard work!!!
 

Offline zhoukevin

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #151 on: May 17, 2022, 10:00:41 am »
Hi there!

Awesome work you guys have done!
Have you seen that some guy have implemented open source firmware for those batteries?
https://github.com/dr-mark-roberts/open-dyson-battery
It's kind of limited functionality but I've been running it in my V6 and V8 batteries for several months with no issues.
Hello, I don't have a compilation environment here. Please send me a copy of the compiled hex file. Thank you! zhoukaier@hoamil.com
 

Offline Hank

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #152 on: May 18, 2022, 07:55:19 pm »
It's done.  :D

After much delay, I'm pleased to announce the release of:

Thanks again for your effort, a sterling job I might say. :-+
And I've got 1 pack charging right now, but when I raise the charging voltage above 25 volts, it starts flashing 8 X red, which indicates charging overcurrent, but that's not the case.
I thought that the original charger outputs 26 volts?
 

Offline suenbrad

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #153 on: May 19, 2022, 07:06:58 am »
I have encountered a v7 battery that can be charged and discharged normally after treatment, but I don't know why the charging voltage can be adjusted below 24.5v to be able to charge normally. If it exceeds this voltage value, the red light will flash and cannot be charged (provided I replace it with it). The batteries are not brand new, I don't know if this has anything to do with it).Because there is no original charger.
« Last Edit: May 19, 2022, 09:31:33 am by suenbrad »
 

Offline Hank

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #154 on: May 19, 2022, 07:57:01 pm »

 Hello, I don't have a compilation environment here. Please send me a copy of the compiled hex file. Thank you! zhoukaier@hoamil.com
The HEX-file is just out there, I'd suggest watching the YT video.
 

Offline tinfever

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #155 on: May 19, 2022, 10:47:02 pm »
Just a heads up for everyone, if your post is related to my firmware, the best place to post any questions or feedback would be in the dedicated thread here: https://www.eevblog.com/forum/projects/fu-dyson-bms-an-(unofficial)-firmware-upgrade-for-dyson-v6v7-vacuum-bms/



Hi there!

Awesome work you guys have done!
Have you seen that some guy have implemented open source firmware for those batteries?
https://github.com/dr-mark-roberts/open-dyson-battery
It's kind of limited functionality but I've been running it in my V6 and V8 batteries for several months with no issues.
Hello, I don't have a compilation environment here. Please send me a copy of the compiled hex file. Thank you! zhoukaier@hoamil.com

I don't think there is a published hex file for his project.

For my project, you can find the published hex file under Releases in the git repository: https://github.com/tinfever/FU-Dyson-BMS



It's done.  :D

After much delay, I'm pleased to announce the release of:

Thanks again for your effort, a sterling job I might say. :-+
And I've got 1 pack charging right now, but when I raise the charging voltage above 25 volts, it starts flashing 8 X red, which indicates charging overcurrent, but that's not the case.
I thought that the original charger outputs 26 volts?

That's odd. I'm pretty confident the CHARGE_OC_FLAG error can only be triggered if the Charge OC bit asserted by the ISL94208.
Since you mention controlling the voltage, I'm assuming you aren't using the original charger? You are correct that the original charger is rated for 26.10V @ 780mA. I just measured mine at 25.99V open circuit. If you are using some other power supply, are you able to measure the current that passes when this error occurs?

Also, does the error occur immediately? Or only after some time?

If you are using a bench power supply, is it possible when you turn it on when set to 26V it is taking some time before it regulates the current down to what you have it set to?

I have encountered a v7 battery that can be charged and discharged normally after treatment, but I don't know why the charging voltage can be adjusted below 24.5v to be able to charge normally. If it exceeds this voltage value, the red light will flash and cannot be charged (provided I replace it with it). The batteries are not brand new, I don't know if this has anything to do with it).Because there is no original charger.

Assuming that when you say "treatment" you mean my firmware was installed, what error code are you seeing? Does your issue sound similar to the one Hank posted about?
 

Offline suenbrad

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #156 on: May 20, 2022, 11:52:29 am »
V6 situation:When using the charger, the yellow light flashes twice first, the blue light flashes once quickly and briefly, and the red light flashes eight times.
The highest voltage cell in your pack is 4.05V. The lowest voltage cellis 3.93V. 4.05V - 3.93V = 120mV difference. 120mv / 50mv per flash = 2 flashes (2.4 rounded to 2)
CHARGE_OC_FLAG   ISL94208 asserted flag that the charging current was over the charge over-current limit
V7 situation:When using the charger, the yellow light flashes first, the blue light flashes once quickly and briefly, and the red light flashes eight times
The highest voltage cell in your pack is 4.09V. The lowest voltage cellis 4.05V. 4.09V - 4.05V = 120mV difference. 40mv / 50mv per flash = 1 flashes (0.8 rounded to 1)
CHARGE_OC_FLAG   ISL94208 asserted flag that the charging current was over the charge over-current limit

I'll try to balance the battery manually first, maybe it's also caused by the old batteries, and I'll report the results to you when the new batteries are replaced.

2022/5/22. Using 6 new batteries Sony vtc6 3000mah, the charging voltage must be adjusted to 25.8v for normal charging. If it exceeds, the red light will flash 8 times.
« Last Edit: May 22, 2022, 03:01:24 am by suenbrad »
 

Offline abraziff

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #157 on: May 26, 2022, 06:09:10 pm »
Hi guys, can you help me?
i have dyson v8 with battery sv10, and the problem is 4 red lights blink.
I disassembled battery, first cell was 3.7V, and other 3.95-4v. I've charged first cell up to 3.95v, and with the same result.  Then i bought a cheap chinese pickit 3, it read firmware, and i think it read it incorrectly. Please check it and provide me with the working firmware.
Thanks.
 

Offline Bartman1001

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #158 on: May 29, 2022, 06:04:55 pm »
I solved 8 Red flash issue. I added series resistor to charge port for reducing charge current. When I add 1.2ohm resistor it solved charge over current error. When I measured charge current, I get a max 800mA. Not even Close to 1.4A limit. So I ,ncrease to sense time from 2.5ms to 5ms in isl94208.c file (tinfever firmware). It solved now.
« Last Edit: May 30, 2022, 07:26:27 am by Bartman1001 »
 

Offline suenbrad

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #159 on: May 29, 2022, 11:22:54 pm »
Thank you Bartman1001 for your sharing to try this firmware tonight
 

Offline dvd4me

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #160 on: May 31, 2022, 02:38:01 pm »
1. Manually balance the battery to 3.7V.
2. Take a thin wire to briefly connect REST (PIN26) and GND (PIN28).
    Nothing happened, still no solution.If you press the button of the battery first, the red light will start flashing. At this time, the red flashing light will go out when you connect Rest and GND for a short time, but it will start flashing red immediately after removing the connection.

Hello, I just had the time to go thru the latest posts, it's been a while. I see in your nice pictures another small 8 pin chip, that must be the flash memory where the program is stored, clear the top with some paint remover and let us know the printed code. There must be some access to program the eeprom since the the programmer holes are there. All these new implementations of the BMS are hard to track.
Since nobody had a chance to work on a pack like yours there is not much info. This is a good chance to see more. If that's a flash chip then inside must be the location of the "red light lock" since it has to be stored permanently, not to be cleared by a hard " reset".
BTW crazy cool tool you have there, I'm waiting to get rich and buy myself one... :) 150$ on Amazon here, it's a gift I would love to give to myself, when it comes my birthday :)))

« Last Edit: May 31, 2022, 02:47:28 pm by dvd4me »
 

Offline suenbrad

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #161 on: May 31, 2022, 08:12:00 pm »
U1:BQ769300 88TG4
U2:ATSAMD20E15A
8PIN:MV393I
 

Offline palacios

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #162 on: June 01, 2022, 06:18:13 am »
Folks, I registered in this forum solely to thank you, and specially Tinfever and dvd4me, who's astonishing work led me to dismantle the Dyson of my wife, to buy a Pickit 3 and mobilise my engineering degree ooooold knowledge in micro electronic.
I managed to get back blue light !
- Used a Trustfire magnetic charger to rebalance manually one or two accumulators that were clearly off balance
- Found on line 10 of EEPROM the values 5A and 09 on the two last figures, and replaced, as in the video of dvd4me by 00 and 7F

Plugged charger and got blue light.

One question, that I think is very related to unproper manual balance, is that some time I see an intermitent amber light on the LED, but it is sporadic for now.

Thank you guys, so much. So much. This is an action for nature and avoiding waste. Your explanations were very clear. Very good, very interesting.
I just can't believe how good people can be on this planet.
 
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Offline dvd4me

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #163 on: July 12, 2022, 11:23:45 pm »
Folks, I registered in this forum solely to thank you, and specially Tinfever and dvd4me, who's astonishing work led me to dismantle the Dyson of my wife, to buy a Pickit 3 and mobilise my engineering degree ooooold knowledge in micro electronic.

Your enthusiasm is a good incentive to keep things moving in the battery repair area. Dyson was just an expensive example. Happy you made-it work.
Check the balancing with a voltmeter after some charge/discharge cycles to see if your cells are still healthy.
An intermittent amber could be the thermistor, it's 10K, if you try to change the cells there is a chance you can break-it.
Power tools cells are also worth saving, 100$ 5Ah pack is a little treasure chest waiting to be found.
Check my repair/revival video of a Rigid pack here:



I have found and fixed 2 over discharged packs, they work just fine now. I bought a Rigid drill just to use the batteries..  :-DD

Have fun
« Last Edit: July 12, 2022, 11:26:05 pm by dvd4me »
 
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Offline colinng

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #164 on: July 26, 2022, 02:52:48 am »
I managed to use a PICkit2 compatible to reprogram location 1E to 00 - and it worked - on a V6 pack that had 32 blinks. Thanks!

The original PICkit2 software doesn't support the PIC16LF1847, but PICkit- (PICkit minus) at http://kair.us/projects/pickitminus/ does! It adds support for hundreds of newer chips, and works with both PICkit2, PICkit3, and in my case, a PICkit2 compatible.

Update: I tried the same thing (1E to 00) on a V7 pack that had 20 blinks --> did not work.
Also tried (1E to 00) and (1F to 7F) but it also didn't work.
I verified every write with a read, and it was set correctly.
However once I start the pack up (magnet + switch) it does the 20 blinks, and when I read back, 1E is now B0. Before any changes 1E was 9E (which I changed to 00).
The QR code inside the pack (which is 18650 with lots of padding) is VAL16108600212, made in Malaysia.
« Last Edit: July 27, 2022, 10:01:42 pm by colinng »
 
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Offline dvd4me

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #165 on: July 28, 2022, 03:20:11 am »
I managed to use a PICkit2 compatible to reprogram location 1E to 00 - and it worked - on a V6 pack that had 32 blinks. Thanks!
That's nice, good to hear that.

Update: I tried the same thing (1E to 00) on a V7 pack that had 20 blinks --> did not work.
20 blinks? This is a new blink code. Battery unbalance for a V7 I remember it was 2 red and 1 blue... or 32, as in the V6.
I made those videos from the packs I have that were unbalanced only.
If there is another type of problem then for sure it will persist after reset until you fix the problem.
Try to find out what 20 blinks mean, I have no idea.
I am not looking to go back to play with those batteries again, there's nothing interesting for me.
The first V6 unlocked pack still works very well after balancing. And I have 2 spare also from the recycling.
Tinfever made a custom FW, if you want to erase your BCM and load that, you can try. There's no going back to Dyson fw.
Dyson FW I like because of the good charging voltages, comparing to the other asian clones of the BCM.
The clones overcharge the cells over 4.2V, that was scary when I was first monitoring the charge.
That's the reason I still stick with the original FW, it was well made ( despite the lock and lack of balance).
Cheers
 

Offline gpoint

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #166 on: August 03, 2022, 03:57:42 am »
Hi there,
I came across your post. it's awesome, really thank you for the sharing (I used to be a firmware engineer on Pic processors long time ago).
I recently opened a v7 battery pack just been curious about the BMS.
I am not familiar with the firmware, can you please help with my question:
Why didn't I get any voltage from the two output pins even while the trigger button (the normally close switch) is pressed (I am sure the BMS is not faulty)?
Does it require certain load or some common grounding to "wake up" the BMS?

Thanks in advance.
 

Offline tinfever

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #167 on: August 03, 2022, 05:49:29 am »
If you
Hi there,
I came across your post. it's awesome, really thank you for the sharing (I used to be a firmware engineer on Pic processors long time ago).
I recently opened a v7 battery pack just been curious about the BMS.
I am not familiar with the firmware, can you please help with my question:
Why didn't I get any voltage from the two output pins even while the trigger button (the normally close switch) is pressed (I am sure the BMS is not faulty)?
Does it require certain load or some common grounding to "wake up" the BMS?

Thanks in advance.


If you have a V7 battery pack, you have to have a magnet near the reed switch on the BMS board, in addition to pressing the button on the battery pack, in order for the output to be enabled, assuming all else is working properly. Also, if using the stock firmware, the output will be disabled after a few seconds if there is not a load of at least a few amps (I think).

Let us know what the LEDs are doing if this doesn't answer your question.  :)
 

Offline gpoint

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #168 on: August 03, 2022, 06:12:51 am »
Hi Tinfever,
So many thanks for the input.
Will give it a go by putting a magnet strip next to the switch, and see how it goes from there.
BTW, how do u find out this?

Cheers.
 

Offline gpoint

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #169 on: August 09, 2022, 12:12:26 am »

If you have a V7 battery pack, you have to have a magnet near the reed switch on the BMS board, in addition to pressing the button on the battery pack, in order for the output to be enabled, assuming all else is working properly. Also, if using the stock firmware, the output will be disabled after a few seconds if there is not a load of at least a few amps (I think).

Let us know what the LEDs are doing if this doesn't answer your question.  :)

Thanks Tinfever,
Your idea worked very well, I used hot gun glued a magnet near the reed switch, it woke up the BMS nicely. The LED doing what it should (blue on to indicate output on).
Somehow the battery packs were not happy with high current drawing from my eBike motor and gave an odour of burning when used for upslope.
But it was a good try though...

Cheers.
 

Offline diebog

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #170 on: August 10, 2022, 10:34:23 pm »
hey guys, im new to the forum but have been on it for many years reading/researching but just finally joined.

So I have an SV10 off an V8 Dyson and unknowingly I removed the board before I knew to unsolder a wire from the switch, my goal was to balance the cells and put it back together as the cells were healthy and not even a year old, well as you might of guessed, it bricked the battery.  Went to put together and got 5 red 1 blue, so I tried doing the reset with a pickit3 knockoff and while it reads and writes fine and the red light went away but now i get a single blue blinking light that doesn't stop.   I wish I had the foresight to save the original hex file but I didn't.    And I did uncheck "program Memory" ahead of all this. The pic on this is an PIC16L1F1847.  Any suggestions?  Does anyone have a good hex file for this model?  Ive thought about buying a working used Dyson brand one off eaby and getting the hex off it to fix this one.  But thought Id ask first. 
 

Offline davegsm82

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #171 on: August 18, 2022, 03:31:32 pm »
@tinfever I just wanted to come and drop a post on the board since this is a journey I've recently been on myself. I was given my mothers old handheld which would only work for a few seconds before cutting off, plugging and unplugging the charger would get it going again so I thought a balance might be in order.

Disassembled the battery pack to try and balance it, but found that oddly all the cells were still in good balance so disassembled further and after dis/reconnecting the PCB to the cells was greeted with the 32 blinks of death. Found the same thing as you guys, the PIC and it's EEPROM data but since it was bricked, meant it was fairly useless.

So I did what any self respecting particle accelerator engineer would do, bought a job lot of 'faulty' or more accurately in this case 'untested' batteries from ebay after the seller informed me that only 1 or 2 were completely knackered. Dumped the EEPROM data from a good one and uploaded it to my bricked one with the PICKIT3 clone and a little adapter plug that hits the pins on the PCB. That brought it back to life even though most of the EEPROM data was different, so I then bricked it again, read out the EEPROM and found the changed bytes. Changed them back and got it functional again.

So, my quick question to tinfever would be, does any of the EEPROM data look like configuration data for the BMS chip? I'm guessing some of it is likely to be info like battery parameters (min/max safe charge voltage/current etc) but does anything you (or anyone else?) has extracted, look like data that is dumped directly into the BMS chip's configuration registers? i'd be interested to find out if there's any information we could garner about remaining capacity, dis/charge cycles etc once the bulk of the EEPROM data has been ruled out.

hey guys, im new to the forum but have been on it for many years reading/researching but just finally joined.

So I have an SV10 off an V8 Dyson and unknowingly I removed the board before I knew to unsolder a wire from the switch, my goal was to balance the cells and put it back together as the cells were healthy and not even a year old, well as you might of guessed, it bricked the battery.  Went to put together and got 5 red 1 blue, so I tried doing the reset with a pickit3 knockoff and while it reads and writes fine and the red light went away but now i get a single blue blinking light that doesn't stop.   I wish I had the foresight to save the original hex file but I didn't.    And I did uncheck "program Memory" ahead of all this. The pic on this is an PIC16L1F1847.  Any suggestions?  Does anyone have a good hex file for this model?  Ive thought about buying a working used Dyson brand one off eaby and getting the hex off it to fix this one.  But thought Id ask first. 

@diebog - as far as I know, no one has yet found an un-protected PIC in one of these batteries, meaning the firmware can't (easily) be extracted. I've looked into having PIC protection defeated in the past and it's a minefield, there isn't one particular method which works for all chips and it's a very hit-and-miss process. One way that is used currently is to decap the chip and (somehow) manually disable the code protection bit, but that's very specialised and very expensive. Are you aware that tinfever has written an alternative firmware that you can use to unbrick your battery though?
 

Offline diebog

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #172 on: August 18, 2022, 07:24:48 pm »

@diebog - as far as I know, no one has yet found an un-protected PIC in one of these batteries, meaning the firmware can't (easily) be extracted. I've looked into having PIC protection defeated in the past and it's a minefield, there isn't one particular method which works for all chips and it's a very hit-and-miss process. One way that is used currently is to decap the chip and (somehow) manually disable the code protection bit, but that's very specialised and very expensive. Are you aware that tinfever has written an alternative firmware that you can use to unbrick your battery though?

Hi, thanks for the reply.  After reading the forums I did find his firmware and on my Dyson V8 SV10 battery I can confirm his firmware works!  Thanks tinfever!  on the SV10 it changes the led pattern from how it used to display but no biggie, at least the pack is up and working again.  Only thing is I can only use it on the low suction setting which lasts for 20 mins or so.  But even with a fully charged battery when I try the high suction mode I get like 5 seconds and then it cuts the power and blinks the blue led 3 x, 3x, 3x, 3x then back to a solid blue led on and after that led turns off (I’m guessing it goes to sleep) only after the last led turns off can use the vacuum again, and once I can the led blinks 6 times indicating it’s still fully charged.  My thought was even though I balanced charged the cells before I put the pack back together, maybe I didn’t do it correctly and the cells are still out of balance so when the high output is used the BMS sees the unbalance and cuts off power?  I’m going to check cells again and and see if that could be the case.   Does anyone know of a sequence to properly balance the cells?  I’m using a Hyperion 6 cell charger (which I use for my Traxxas batteries) with the balance wires soldered on the leads of battery, I first used the balanced function which lowers all the rest to the lowest cell and once finished I use same charger to charge which is also balancing them as it charges.  Only thing I didn’t do is to let the battery sit after the first balance, perhaps the cells need to sit to settle down to their nominal voltage and then rebalance a second time before charging? 

Does anyone know of an aftermarket BMS for these batteries that will actually balance charge the cells?  I bought a battery off Amazon (First Power Brand) to try out and after I charged it and discharged it a few times I did a time test with out the carpet head and on low setting and the battery only lasted 10 min when they advertised 35-40 min. Either I got a bad battery or they are full of crap!  I’m leaning towards the latter.   But I opened that battery up to see if they were at least balance charging them and found the circuit board had all the populated slots to solder the tabs going to each cell, however they weren’t even being used as there was no tabs/leads coming from the other cells even though there were spots for them in the shell moldings.  And looking close the populated slots don’t have any traces going anywhere top or bottom of PCB. 

« Last Edit: August 18, 2022, 09:59:11 pm by diebog »
 

Offline tinfever

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Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #173 on: August 18, 2022, 09:53:00 pm »

So, my quick question to tinfever would be, does any of the EEPROM data look like configuration data for the BMS chip? I'm guessing some of it is likely to be info like battery parameters (min/max safe charge voltage/current etc) but does anything you (or anyone else?) has extracted, look like data that is dumped directly into the BMS chip's configuration registers? i'd be interested to find out if there's any information we could garner about remaining capacity, dis/charge cycles etc once the bulk of the EEPROM data has been ruled out.


I honestly haven't analyzed the stock EEPROM data much. However, I would guess it is mostly logging data and also a record of tripped flags. For example, when you run the vacuum until the battery gets too low and cuts out, it remembers that it had a low battery cutout and even if the PIC loses power (like it does when the BMS board goes to sleep), it remembers that flag was set and only clears it when you connect the charger.

I'd guess the min max voltages and safe current settings are all hardcoded in the firmware. EEPROM would only make sense to use for data that changes over the use of the battery. For anything that is always the same, like the cell low voltage cutoff limit, I don't see why they'd use any of the precious 256 EEPROM bytes.

The BMS IC doesn't actually have much configuration loaded in it, other than the overcurrent and short circuit levels and time windows, and few other boring operational settings. Nearly all the smarts are in the MCU.

I'm glad it sounds like you had success in repairing your vacuum, or at least bringing someone else's battery back to life  :D

When you said that the cells were balanced but the vacuum was still cutting out very quickly, those may be cells that have legitimately aged and now have higher ESR (a normal age/use degradation thing I think). High ESR cells may measure fine with no load, but as soon as you apply a load to them, their voltage plummets. A good cell might have an ESR of 50mOhm, so 3A draw (normal vacuum power) might cause cell voltage to drop 150mV, like going from 4.20V to 4.05V while the load is applied. A high ESR cell with something like 350mOhm (random number I made up) would drop from 4.2V to 3.15V, which is very close to the 3V cutout. Thus, you get very little time until it cuts out but as soon as you remove the load, the cells measure OK.

Hi, thanks for the reply.  After reading the forums I did find his firmware and on my Dyson V8 SV10 battery I can confirm his firmware works!  Thanks tinfever! on the SV10 it changes the led pattern from how it used to display but no biggie, at least the pack is up and working again.

I'm glad it worked for you!  ;D


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Only thing is I can only use it on the low suction setting which lasts for 20 mins or so.  But even with a fully charged battery when I try the high suction mode I get like 5 seconds and then it cuts the power and blinks the blue led 3 x, 3x, 3x, 3x then back to a solid blue led on and after that led turns off (I’m guessing it goes to sleep) only after the last led turns off can use the vacuum again, and once I can the led blinks 6 times indicating it’s still fully charged. 

I'm curious, was the battery able to operate longer in high suction mode before installing my firmware? What it sounds like is happening is under the high suction mode (draws 17A vs 3A in low suction mode) any higher ESR of the battery cells is greatly exacerbated like I describe earlier in this post.

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My thought was even though I balanced charged the cells before I put the pack back together, maybe I didn’t do it correctly and the cells are still out of balance so when the high output is used the bms sees the unbalance and cuts off power?  I’m going to check cells again and and see if that could be the case.   Does anyone know of a sequence to properly balance the cells?  I’m using a Hyperion 6 cell charger (which I use for my Traxxas batteries) with the balance wires soldered on the leads of battery, I first used the balanced function which lowers all the rest to the lowest cell and once finished I use same charger to charge which is also balancing them as it charges.  Only thing I didn’t do is to let the battery sit after the first balance, perhaps the cells need to sit to settle down to their nominal voltage and then rebalance a second time before charging? 

My firmware doesn't lock you out if the cells are far out of balance. However, it will shutdown with those 3 blue blinks if any battery cell goes too low. Of course, it can only charge the battery pack until the highest cell hits 4.2V, and only discharge the pack until the lowest cell hits 3.0V, so if the pack it out of balance, you'll get diminished usable battery capacity.

I don't claim to be a Li-Ion battery expert, but I don't think there is a terribly wrong way to balance a pack. As long as the cell voltages are all close together after letting the pack sit for a few minutes, I'd consider it successfully balanced. The way I would recommend balancing it, at least with a bench PSU, is to charge the battery pack with the normal charger until full, then charge the cells individually with the bench PSU set to 4.2V and a current limit of maybe 500mA (all assuming no cell is terribly low like 2V). Once the cell being charged goes in to current  voltage mode, you'll see the current going in to the cell slowly drop. Once it drops to maybe 50mA, you can probably consider it done. Rinse and repeat for any cell below 4.2V. Once you are done going through all the cells, they should all be pretty close to 4.2V. They will drift a bit after you stop charging though.

At that point, you could call it done balancing. Or to be extra thorough, you could use the battery pack until low voltage cutout, charge it back up again with the normal charger, and then recheck the cells and rebalance any lower ones.

Using the cell charger that also balances like you described also sounds perfectly fine. As long as all the cells are close together and all near 4.2V when completely, I'd call it a success. Waiting a few minutes and rebalancing isn't going to hurt anything either though.

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Does anyone know of an aftermarket BMS for these batteries that will actually balance charge the cells?  I bought a battery off Amazon to try out and after I charged it and discharged it a few times I did a time test with out the carpet head and on low setting and the battery only lasted 10 min when they advertised 35-40 min. Either I got a bad battery or they are full of crap!  I’m leaning towards the latter.   But I opened that battery up to see if they were at least balance charging them and found the circut board had all the populated slots to solder the tabs going to each cell, however they weren’t even being used as there was no tabs/leads coming from the other cells even though there were spots for them in the shell moldings.  And looking close the populated slots don’t have any traces going anywhere top or bottom of PCB. 

That's disappointing to hear the battery off Amazon doesn't even monitor the voltages on each cell, let alone balance them. Unfortunately I haven't worked with any of the aftermarket BMS's or batteries so I can't help much there.  :)


 

Offline diebog

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  • Posts: 6
  • Country: us
Re: Dyson v7 Trigger cordless vacuum - TEARDOWN of battery pack
« Reply #174 on: August 18, 2022, 10:42:52 pm »

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When you said that the cells were balanced but the vacuum was still cutting out very quickly, those may be cells that have legitimately aged and now have higher ESR (a normal age/use degradation thing I think). High ESR cells may measure fine with no load, but as soon as you apply a load to them, their voltage plummets. A good cell might have an ESR of 50mOhm, so 3A draw (normal vacuum power) might cause cell voltage to drop 150mV, like going from 4.20V to 4.05V while the load is applied. A high ESR cell with something like 350mOhm (random number I made up) would drop from 4.2V to 3.15V, which is very close to the 3V cutout. Thus, you get very little time until it cuts out but as soon as you remove the load, the cells measure OK.

Can I use a standard DMM on the \$\Omega\$ setting and test a cell?  Or would I need an ESR capable meter?


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I'm curious, was the battery able to operate longer in high suction mode before installing my firmware? What it sounds like is happening is under the high suction mode (draws 17A vs 3A in low suction mode) any higher ESR of the battery cells is greatly exacerbated like I describe earlier in this post. 

So no the vacuum wasn't able to run longer in high suction mode, its the same.  Before I messed with the pack when it was fully charged it would only last a short time and the BMS would cut power.  But the battery was still charged.  So your probably right about one or more cells have high resistance.  I figured that sense this vacuum was only a year old or so that they were fine, just out of balance, so I stupidly (without researching first) removed the board to check stuff out which bricked it because I didn't know to remove the wire from the switch. |O

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I don't claim to be a Li-Ion battery expert, but I don't think there is a terribly wrong way to balance a pack. As long as the cell voltages are all close together after letting the pack sit for a few minutes, I'd consider it successfully balanced. The way I would recommend balancing it, at least with a bench PSU, is to charge the battery pack with the normal charger until full, then charge the cells individually with the bench PSU set to 4.2V and a current limit of maybe 500mA (all assuming no cell is terribly low like 2V). Once the cell being charged goes in to current  voltage mode, you'll see the current going in to the cell slowly drop. Once it drops to maybe 50mA, you can probably consider it done. Rinse and repeat for any cell below 4.2V. Once you are done going through all the cells, they should all be pretty close to 4.2V. They will drift a bit after you stop charging though.

Thanks for that info, im very new to lipo hacking so other then use the Hyperion EOS0606i I haven't done much manual charging of cells.  Ill give that a try and see where it takes me.   :-+

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That's disappointing to hear the battery off Amazon doesn't even monitor the voltages on each cell, let alone balance them. Unfortunately I haven't worked with any of the aftermarket BMS's or batteries so I can't help much there  :) 

Ya I was very disappointed to find that out.  The brand "FirstPower" on Amazon had decent reviews and was one of the more costly brands but was odd that the battery did not have a manufacturer name on it, so I think there are just multiple sellers of the same battery coming out of a couple of factory's and they sell them however they want like allot of the rebranded items we see nowadays.  This one was listed as 5.0Ah which is impossible because these are in series so it goes off what 1 cell is which is more like 1.5Ah or something.  The battery I got wasn't anywhere near the stock 2.8Ah

 So I thought there would be a market out there for a good BMS for these that actually checks and balances the cells properly.  I would diffidently be interested in replacing mine if it made the cells last along longer and had the bonus of resetting/open source if you needed to replace the cells.  But I guess if one is willing to open the pack to replace the BMS they will most likely are to just use a bench top power supply and manually charge like you explained above.
 


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