Hybrid (HV) battery test proposed

I will give this test a "go" in a couple of days. Most likely Sunday. Will report back what I find.

 

Thanks for posting that data Ron. Actually I'm beginning suspect that your Prius is normal (4 minutes) and that the OP's data is in error (possibly gotten his own procedures wrong). The OP's procedure is very clear, start at the nominal 6 bars and wait until that bar drops and then time how long it takes for the NEXT bar (that would of course be the 5th bar) to drop. What I suspect has happened is that despite clearly writing the procedure, that the OP has perhaps assumed that it doesn't make any difference and hence posted the 6th bar time instead (time from when 7th first drops until when 6th first drops).

The reason I say this is because the 5th bar represents much less capacity than do the 6th and 7th bars. The 6th bar is about 8 or 9 percent of the total (6.5 Amp hours) while the 5th bar is only 3%. So as you can see we totally expect the 6th bar to last 2.5 to 3 times longer than the 5th, which is exactly consistent with your data.

Follow the upper steps in the following figure to see the discharge capacity levels of the Prius battery (following the lower trace of the boxes gives the charging profile, the upper trace the discharging profile).

 

Adding to the above. The other thing that makes me suspicious that the OP's nearly 11 minutes was not recorded for the 5th bar, is that even with a close to 100% new capacity traction battery, the power drain implied by this is only about 200 Watts (based on 3% of 6 AH over 10.5 minutes).

That (200W) just seems too low, considering that this has to power the DC-DC converter and all of the 12V systems (including battery charger) AND provide the motive power as well! It just seems unlikely to me, especially since people here have estimate that the minimum load on the 12V system alone in ready mode is around 130 to 150 watts!

 

Another thing to consider is that the battery is I believe in total 6.5 AH but 60% of that capacity is not used. Never charged higher than 80% never discharged below 40%, that is 3.9 AH subtracted from 6.5 = 2.6 AH working capacity.

John (Britprius)

 

Yes John, the above chart (and my calculations based on it) definitely take that into account.

 

This will give an approximate working capacity in watts of 570. Reasoning that the average battery voltage will be about 220 volts.

I will be able to do the test myself tomorrow, to clear any confusion using the blue band below the first green. I will also be able to check a friends car as I am fitting a 12 volt battery for him.

John (Britprius)

 

Yeah, somewhere about that. Since the rated AH's of a NiMH (or NiCD) cells is often rated right down to about 1.1 or even 1.0 volts (though of course most of the discharge cycle will be more like 1.25) I'm usually a bit more conservative with my estimate of the voltage (under discharge). I figure more like 520 Watt-hrs, but give or take a bit I agree with you. These tests aren't going to be totally accurate anyway, there will be temperature difference and also some unavoidable differences in electrical loading (eg 12V battery charger consumption, battery cooling fan consumption) that the user has no control over. Actually I'm not even 100% sure that the default (zero accelerator position) traction power demand is going to be identically calibrated on all Prius anyway.

 

From memory I believe my "zero accelerator position" is at 17% from the data from Techstream.

John (Britprius)

 

Just check throttle position on my lap top and it's set at a "value" of 16%.

John (Britprius)

 

That should be 2.6 ah * 192 volts = 499 watts, calculated on the nominal voltage. No different than a 12 volt battery which gets all calculations done on a nominal voltage of 12 even though resting voltage is 12.7 and surface charge coming off of a charge is usually over 13.

 

If I recall correctly, the nominal voltage is 201.6 volts. That's 28 by 7.2 volts if you go by modules, and 168 by 1.2 volts if you go by individual (internal) cells.

 

Results from 2 cars "my own 2008 with 90,000 miles:-

First blue bar (6) 10 mins 50 seconds
Next blue bar (5) 4 mins 15 seconds
Next blue bar (4) 4 mins 11 second

Battery temps started at 10C finished at 13.1C
Battery current was about 1 amp "varying slightly"
Outside air temp 6C

Friends car "2007 with 89,000 miles :-

First blue bar (6) 10 mins 41 seconds
Next blue bar (5) 4 mins 18 seconds
Next blue bar (4) 4 mins 4 seconds

Battery temp started at 8C finished at 11.9C
Battery current 1 amp varying
Outside air temp 6C

Results come out almost identical.

John (Britprius)

 

Thank you John for posting your data. That makes me feel a little better. Interesting string, and thanks to Uart for your input also. It is most appreciated.

 

So it looks like about 10m30 sec is normal for the 6th bar and 4m15s is typical for the 5th bar. I say it's pretty certain now that the OP was measuring the 6th bar all along.

 

My bad, you are right. I was thinking about my lead-acid battery bank, and I was tired!

 

Here are my results. Not sure though I did the test correctly. I tried to turn everything off. Did that include the display on where you read the speedometer? That was on. Everything else was turned off. Put emergency brake on and vehicle in "d."

My vehicle: 2005 prius with 105,000 miles. Temperature: 46 farenheit

After the green went into blue is where I timed the sequences:
6th bar to 5th bar: 9:41
5th bar to 4th bar: 2:27
4th bar to 3rd bar: 42 seconds

Not sure how to interpret these results.

 

Yep it sounds like you did everything correctly there NJ.

Had the car been driven prior to the test? If your battery was 46F then that might account for slightly lower readings than others. Like 9:41 versus 10:30 is pretty much within the sort of variance we expect here. The 5th bar seems a little lower than expected, but the 4th bar seems way low. You're sure there weren't any electrical loads that got switched on towards the end there?

 

Without more data, it will be difficult to determine what is good and what is bad. I do agree that the 46F temp could cause the test to show variations as it did.

Probably the only way to truly test this would be to take the same car and run the test under various temps to confirm whether the temp causes it to vary.

I do agree that NJ's number's are less than other's in certain time frames, however I also must note that John's (BritPrius) times were better than mine.

It will be interesting to see more data as it flows in. As I said earlier, this is a interesting string.

 

I remember somewhere reading (maybe on this forum), that to test the battery you can shift to R and hit the brake and accelerator pedal at the same time and observe how fast you drain the battery. Not exactly sure if it's the right procedure but the R gear was definitely involved and ICE must not come on, maybe was in EV mode.
Will try to test this on gen III.

 

Just seeing if there were any updates on this string (thread) or if GasperG had anything more to add.

Is additional data still useful or has this test been discounted now.