How to detect on Prius a weak cell

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victor2k
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How to detect on Prius a weak cell

Post by victor2k » Tue Apr 24, 2018 9:47 am

Hello,
The car is a Toyota Prius /NHW20/2009 year with warning lights in dashboard.Using a scanner I see in HV Battery ECU P0A80-Replace Hybrid Battery pack.
P0A80.PNG
Then I looked at the freeze frame for this fault code.
BLOCK 05.PNG
Using this I found block 5 and 8 faulty(the voltage drop too much in the discharging phase).The HV battery use 28 cells(7,2v each,6 elements in one cell),in diagnose you will see 14 blocks(2 cells in 1 block)
Now is the time to find the faulty cell.Both cells were taken from the same HV battery(block 05),so the discharging rate must be the same. I placed in series this two cells and a 21w/12v bulb- the discharging process was captured with the scope:
the voltage from a good cell on channel A,
the voltage from a bad cell on channel B,
the discharging current on channel C
Toyota_Prius_2009_Petrol_20180424-0001.psdata
(3.43 MiB) Downloaded 247 times
At the minute 15 you can see a drop of cell voltage(only at the bad cell) so the bad cell was discovered.
The voltage drop is easy to see,the current drop not.
How can be used this infos to calculate the cell capacity(a new one must have 6,5Ah)?Will be needed more datas?Just tell me what you need ...
Best regards.

victor2k
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Re: How to detect on Prius a weak cell

Post by victor2k » Thu Apr 26, 2018 4:30 pm

Hello again,
Today I made a full discharge,do not try this at home!
Here you can see how the different 1.2V cells fails in the discharging phase...
here is the bad cell
Toyota_Prius_2009_Petrol_20180430-0001.psdata
(417.52 KiB) Downloaded 199 times
And here is other cell
Toyota_Prius_2009_Petrol_20180430-0002.psdata
(511.55 KiB) Downloaded 166 times
Attachments
IMG_20180430_124702_HDR.jpg

techgear
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Re: How to detect on Prius a weak cell

Post by techgear » Tue Feb 26, 2019 6:45 am

Dear Victor,
this is a really new topic test by pico. Can i ask more about this?
is it mean the bad cell will drop the voltage like a step earily than good cell?
how to get the Ah in the math channel?
look forward to your answers, thanks.

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VASTech
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Re: How to detect on Prius a weak cell

Post by VASTech » Tue Feb 26, 2019 5:00 pm

Hello Victor!
I just see your post.
Please tell me !
I see that you use 4 x 10 ohms resistor on that PCB as load for that cell. Did you use them in parallel mode 2.5 ohms for this test?
Good job!

victor2k
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Re: How to detect on Prius a weak cell

Post by victor2k » Thu Feb 28, 2019 10:53 am

VASTech wrote:
Tue Feb 26, 2019 5:00 pm
Hello Victor!
I just see your post.
Please tell me !
I see that you use 4 x 10 ohms resistor on that PCB as load for that cell. Did you use them in parallel mode 2.5 ohms for this test?
Good job!
Hello,
My module use 2 series resistors for 0,4A discharge current in parallel with two others(the last two can be switched off in the final stage of discharge in order to prevent the cell damage-the deep discharge at high current will overheat and deform the cell).
Best regards

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