ScanGauge for SOC - Question

What you're seeing is correct. The Prius tries to never let the traction battery get fully charged or fully discharged... it will start showing full around 70% charged, as you saw, and it will kick in the ICE to start recharging the battery at about 40% full. This is perfectly normal and is done by design to extend the life of the battery.

The Traction Battery Temp XGauge (as well as a ton of others for the Gen III) is listed on the spreadsheet here...

https://spreadsheets.google.com/ccc?key=0AiHL0r_2nhUEdF9lVVBxOVNoN3Zva3E0NmdZTUR1eVE&hl=en#gid=5

 

For fuel, Scangauge just does a mathematical approximation based off the miles driven, mpg, gallons used, etc., though it has no idea how much is actually in the tank.

 

I think you guys might be looking at two different things... There is an XGauge for fuel level that I believe comes directly from the car and is based on the actual fuel level. If there's a standard gauge on the ScanGauge (I'm not sure if there is or not) that would be based on an estimate. I know that the scangauge does try to estimate how much fuel has been used and you can see that estimate on the fill up screen.

 

When you setup the scangauge you enter the size of your gas tank rounded down to the nearest gallon. This value is used as part of the trip data displays. Miles to empty ect. Each time you fill your tank there is a procedure for making an adjustment in % to the scangauge to fine tune its readout. Its tedious and requires a full tank fillup each time.

 

The actual gallon number is approximate; the gauge itself likely does not cover the full range of the tank (there may be some space at the very top or very bottom of the tank that it can't measure), and the Scangauge is doing some math to approximate the level (specifically, it's multiplying by 5000, and dividing by 3785; aka multiplying by about 1.32 - whoever came up with the Xgauge might be able tell you why. Typically, it would be because the unit from the measurement is different from the unit that is displayed. This would imply that the gauge is measuring in increments of 5 Liters, which would be the same as 1.32 gallons.)

Also, it's not entirely accurate because the computer in the car is averaging the readings, while the Scangauge is just dumping the raw data out. The computer does this so that you don't see the pips come and go (at least, not frequently) each time the gas in the tank sloshes around.

In summary, both the pips and the Scangauge are displaying data from the same source, they just display it differently. (That said, it'd be interesting to see which end causes some pips to last longer than others - is it because the computer says that the tank should appear "full" from, eg, 12 gallons down to 8, or is it because the gauge can only really measure up to 9? If you pay attention for a tank or two, you should be able to figure this out.)

So take it as an advisory number only; if you see it saying 0.25 gallons left and you know you can average 40 miles per gallon, don't plan on hitting the gas station in 10 miles. I think most of us will still recommend filling up when (or shortly after) the last bar starts flashing.