Hybrid (HV) battery test proposed

Lewis, I like what you're thinking...wondering what it would take to make your test more standardised to produce more valid results...I read the concerns on temp. variables, so just pick a standard temp. like 70 degrees at which to do testing.
Would it help, instead of reading bars, to connect a voltmeter to the small wire high voltage tap at the HV battery, and see how long it would take for the ac to cause a drop of, say 5 volts?

 

Guys,

I use Priidash to log my HV Battery test which I perform at the end of my driveway.
Priidash will require a high speed OBD2 dongle such as the ones made OBDsol ,
I would suggest the USB version ( as Bluetooth may not be fast enough, Their WiFi is possible but you will need a USB to WiFi adapter as Priidash likes to talk UART comx Port using a VCP Driver. They use FTDI chips so the VCP driver is available free from the FTDI website.
The OBD2 adapter will need to be programmed using a Terminal Emulator such as TeraTerm to run the UART bus at 2000000 as the factory speed is set at 115,200....this is simple enough to do.
Installation of the Priidash3mfd on a laptop is very simple and can be downloaded from SourceForge and well worth any donated beer.

I does not tell me if my battery will fail next week or next year but it will tell me if I am on the slippery slope below the "Knee" of the discharge curve where mpg will start to drop off and letting it discharge to purple bars could result in a tenuous situation, but all is not lost as it my restart the engine and charge the battery back up to 50%.

I ran a this test where I use the Priidash logs to generate a discharge curve last week and have posted the pdf chart.
The cars ECU likes to run my battery between 50-65% in the urban drives that I do, traffic waits at lights where you creep along will drop the soc down to 3 blue bars.

I have attached a charge/discharge curve.

 

I tried this test on my 2006 Prius with 265000 miles on it. It ran for over an hour before I stopped the test. I never went below 6 lines under load, even with heater on. It would go up to 7 lines and occasionally all 8 green lines: The garage was 5 deg F and the outside temp was -2 deg. We just got over a major polar vortex here in Wisconsin where the temps were -30 a few days.
I should mention that the Red Triangle of Doom and its companion VEC ,check engine and brake lights have been lit up like a Christmas tree for the past month. The dealer got the POA080 hybrid fault code.

So ...is my hybrid battery toast? The car runs fine...except cruise control has stopped. They want 3500 for new battery.

 

Was your engine turning off and on during the test? That would keep the battery charged. And yes your battery is probably done. 3500 seems high. A new battery itself can be had for 1715 plus tax.
Battery - 2004-2009 Toyota Prius (G9510-47031) | Tracy Toyota
An independent hybrid shop could probably do the job for less.