How to test HV battery state of health on your Gen 2 (answer)

There are a few recommendations on here concerning the subject. I have developed a method using Techstream that I feel can apply to anyone with no diagnostic equipment at all.

NOTE: this test has only been verified to work at or above 70°F. I will repeat this test at progressively lower temperatures to determine effectiveness. Additionally, I will devise a "no A/C" multiple for use in colder climates.

Proceed as follows:

1. Read and understand all steps before starting.
2. Test should be initiated when ICE is completely cold.
3. Access the 12V and disconnect the large white plug. Wait 60 seconds and reinstall. This erases the Battery ECU's current SoC approximation.
4. Start car. Allow it to charge at idle. Once it stops charging at idle, force charge as follows:
5. Force charge to 80% SoC (parking brake on, smash and hold brake, in "D", floor the throttle until all green bars and charging arrow is blinking on and off). NOTE: in some cases, the car may refuse to charge above 7 bars. It's normal. Terminate force charge if you experience this. The 12V reset in step 3 should prevent or minimize this occurrence.
6. Set A/C to lowest temperature setting, max fan speed, fresh air intake. The goal is to make the compressor pull the highest load possible.
7. Rear defroster on
8. Low beams on
9. Parking brake on as hard as you can press it AND chock the wheels if possible.
10. in "R"
11. Release foot brake (parking brake always on, confirm you don't roll), do NOT apply throttle.

Do 6-11 as quickly as possible and start a timer. Record the amount of time it takes before the ICE starts (should happen when you have 1-2 purple bars, but it may not be immediate). On occasion the ICE will start momentarily and shut off. A few of these will not influence the test. This actually has a net draw down of SoC as spinning the ICE takes more current than any regen you get from the ICE.

Once the ICE restarts in the 40% SoC area, shut down A/C, defroster, lights and put in park. Allow the car to charge normally at idle.

After the test is completed, I recommend you drive normally until the SoC gauge returns to six blue bars or for 10 minutes, whichever is longer. In hotter climates, the cycle can leave the battery pretty warm.

Convert the # of minutes:seconds to decimal form and multiply by 9.5%

The result will be your battery state of health, i.e., the % of rated capacity.

While "9.5%" precision indicates this might be a precise measurement, it's not. It's what my car produced under Techstream monitoring, so YMMV. I would expect a variance on the order of ±10%, so if you come back with 103% SoC, it's probable your compressor consumes a little less current than mine, and your battery is probably very healthy.

My car with a "like-new" performing battery (2600mAh usable capacity) is the baseline for this test. These results have been confirmed on an '06 with 130K miles and a second '06 with 154K miles with current/capacity measured by Techstream.

Here is what I capture with Techstream:
View attachment 110231
I recommend a reduced data set for faster sampling. The above can be saved as you create it.

I'm not familiar enough with the Gen 3 display to say how it will work, but I expect it will. I haven't confirmed the process as currents might be different, but a trusting coworker will likely let me test it on her car.

Here's a plot of the Techstream output:



Computed capacity was 2,594mAh (2,600 is 40% of 6500). The current was 15-16A and deltaV stayed under 0.3V even at 40% SoC.

This battery is a low mileage pack from a mild climate and had been tested on a module level. All modules met very near rated capacity within 5% - some over, some under.

Thanks for reading,

Steve

EDIT: I repeated this test yesterday. The first test was 10:20. Yesterday was 10:33 without Techstream attached. I'm pretty happy with that consistency. However, I revised the multiple down a bit as I didn't compensate for a couple variables.

EDIT 2: I made the instructions a little more generic and indicated the bright headlights should be on vs. just the regular lights.

EDIT 3: Added the 70°F limitation and changed brights to low beams. They actually draw a little more.

EDIT 4: Tweaked the steps to add wheel chocking and to make mention of the fact that sometimes it won't charge to 8 bars.

EDIT 5: Revised to indicate it should be done when ICE is completely cold and following a 12V reset.

EDIT 6: Added Techstream data capture list.

EDIT 7: Added recommendation to drive the car after the test to ensure the battery does not overheat due to post-test heat soaking.

 

30-40% is where I would expect to see capacity issues impact performance/mileage. Conservatively speaking, I would expect a 50% continued life factor, e.g.,

If it's taken 6 years and 100K miles to get to 70%. I would expect another 50% more life from the pack until 40% is hit, so another 3 years, 50K miles assuming same driver, climate, terrain and driving styles/trips.

Obviously, this is a pure guess, and it's probably less accurate the closer you get to 40%. Capacity deteriorates at an accelerated rate, and the above assumes relatively uniform pack deterioration as I observed in my friend's '08 that tested at 27% capacity prior to grid charge/discharge reconditioning.

 

Per the post, I suspect it will. If what you say is true, then I'm sure it could be modified to work over a different range with a different multiple.

I'll try to conduct that test on my coworker's 2011 this week.

 

My chart is from an export to Excel.

If you recorded it and saved to a techstream file, zip it and post it here.

Where are you located?... and LOL for your avatar. That's cool.

 

My 14 year old and 11 year old are finishing up season 9 of the 2005 reboot now. They started at 1 and have been knocking it out over the past two months.

You can graph SoC, Battery Current, and Min/Max voltages. Hit the "Overlap button" in the bottom right, and you can get something similar. You obviously don't get capacity because that's computed, and you don't get deltaV, you get the min/max values. There's an example in my "quantitative" thread in my sig.

Capacity should be 4.21 mAh * # of seconds between start of ~14A current and ICE start. This is an approximation based on average discharge current of 15A. 2600mAh is 100% SoH.

 

You did not conduct the test as instructed. It does not appear your A/C was on at all. A/C to fresh air, "LO" temp and rear defroster are key to the success of this test. Your peak current was in the vicinity of 6A instead of the 16A the test should produce. Here is the output of your Techstream chart:

View attachment 106914


The little spikes are around 10A, the top of the green hump is about 6A and the bottom is about 4A. Your average is about 5A or 1/3 the desired current. Note how the blue line abruptly drops off. This should be a fairly uniform drop as in the chart at the top. The abrupt drop off is indicative of a severely deteriorated battery. I don't have the numbers computed but your battery is at approximately 30% SoH and is likely to continue to deteriorate to the point of failure in the very near future. You have almost no usable capacity left, and 60% SoC is in the steep part of the blue curve meaning the SoC swings are likely to be high and your voltage drop with load is severe.

I invite you to repeat the test as instructed making sure your A/C is on Fresh inlet, "LO" temp and rear defroster is on. A local PC member contacted me to help with his grid charge installation. We ran a test. His output is as follows:

View attachment 106915

As you can see, the current (green) is pretty steady. At the point the SoC starts to drop abruptly, current is 16.04A and deltaV is about 0.24V.

The encouraging thing about both of those tests is the deltaV is relatively tight. This suggests uniform deterioration of the modules and are excellent candidates for reconditioning through grid charging/discharging.

We are in the process of deep discharging his pack. I hope to be able to do an "AFTER" test for comparison tomorrow... depends how long the discharge takes. We're already in the < 185V zone, but the 25W bulbs draw very low current.

Again, I strongly encourage you to repeat the test per the instructions.

Steve

 

It's also possible that if you're in a very mild climate, you won't get full compressor function. If that's the case, then I'll have to think of an alternate.

 

I specifically stated A/C on LO. "LO" is the setting below 65°F. When the Gen2 controls are set to "LO", the A/C turns on full blast in cooling mode. This may be specific to U.S. spec models.

If the Aus version is different, the goal is to have the A/C on the coldest setting with the highest blower speed and taking in fresh air. The idea is to have the A/C compressor running at maximum load pulling maximum current. This might be reproducible with the heat and front window defrost settings, but I do not know.

The end goal is to pull as much electric power from the battery either directly (A/C compressor and gear selector in "R") or through the inverter (blower, lights, rear window defroster).

Here is an Excel plot of your data. I trimmed the data at the beginning and end to eliminate extraneous data:

View attachment 107001

Things of note:

1. The SoC line falling off rather than a gradual, near constant-slope line is an indication of significant deterioration. I highlighted the region in red between 55 and 65% SoC. Note how the bulk of that region encompasses the steeper part of the blue curve. This indicates that your assist is severely limited as voltage drops occur quickly in that zone. The car registers this as a SoC drop and you likely will see amplified gauge movement.
2. Your DeltaV remains very tight throughout the range. This is a signal that the deterioration is uniform and not associated with a single block.
3. Your average current was low at 5.6A. Under the prescribed 15-16A load or car loads, these would both be exaggerated.

I have also attached the source Excel file. The computed capacity was 999mAh from 81.5% to 39.5% SoC. 100% SoH is 2730mAh at that range, so your SoH is 999/2730 = 36.6%. I regard this as optimistic because your average current was 5.6A, which is approximately 1/3 the 15-16A load the test should produce.

Your battery is definitely near its end of life; however, it is likely a perfect candidate for reconditioning via the Prolong grid charging equipment/process.

I was contacted by a local PC member to install his HA gridcharger/discharger. We conducted this same test over the weekend with excellent results. I'm still working on the charts, but based on approximations, his battery was similarly deteriorated to around 35% and the reconditioning pushed it to about 78%. I will post before and after charts later today in the "Quantitative" thread in my sig.

Steve

 

Actually, it is a package difference. I have only been in 2006/2008 models with a particular offering. I'm revising the original post for more clarity.

EDIT: To actually answer your question... Yes.

 

No bearing with you at all. Happy to help.

I would urge you to act sooner rather than later. Your pack is severely deteriorated even at the reduced load. I am very confident that you could achieve comparable results to the new test I reported in the "quantitative" thread in my sig. Delay only runs the risk of the weakest cell finally giving up the ghost, dropping out and coding requiring either a LOT more work or a lot of money. It would be amazing to see a 300K+ pack recover.