I wonder if there is a time period involved. It does not make sense for the engine computer to reset as soon as the 12V battery is disconnected. Curiously there are no "Effects/Inoperative Functions" listed if the idle speed setting is not initialized.

I dont think the SFI initialization needs to take place. The manual (which I am trying to recall from memory at the moment) stated something about disconnecting the negative battery terminal if you were not going to use the car for a long period of time (over 2 months?) to prevent battery drain. I dont believe it said anything about what to do after you reconnect the battery, so I'm assuming there would be no issues when reconnecting the batter.

Stan/SPL -- Thank so much for attaching those pages!

I'll admit my knowledge of car mechanics is rather limited, but darn!!! one more thing to add to my list of "things I won't be able to fix myself anymore". Since aux batteries usually don't have a long shelf life around here (read: hot summers), this mean yet more $$$ I'll have to shelve out when it's time to replace it.

Couldn't agree more! Even if one would be willing to purchase that $$$$$ intelligent tester, those @#$% instructions don't sound very enticing... Let's see:

(a) Apply the parking brake [...]

(n) Move the shift lever to the D position [...]

(o) Depress the accelerator pedal with your right foot while firmly depressing the brake pedal with your left foot, and maintain an engine load value of 45% or more (60 to 70% of full acceleration) for approximately 30 seconds. Notice: do not perform this step for 40 seconds or more.

Uhhh.. Am I dreaming or did it ask you to firmly hit both the gas AND the brake pedals simultaneously while in "D" (yes, with the parking brake on, but that's just a small comfort)?

Yes, and in a normal torque converter car you will just produce heat in the transmission fluid, but ing a HSD equiped car the output drive will be stopped sending all power to the motor/generator, thus charging the battery.

And speaking of $$$$ - I've read somewhere that the 12v battery is a glass mat battery and these run big $$$$ - a google search shows discounted rates of $140 and up ! Another advantage of having a hybrid... The money you save at the pump can now go inside the store..

Yes, but My own experiance is glass matt batteries last 5-8 years with no problems. I have Optima Glass matts in 6 different units and they will go the distance. a battery with flooded cells will last a long time if you make sure you put water in it. A glass matt battery must be charged at a low rate 1-2 amps top, if you use a maintainer go with a Battery Tender or similuar to float or storage mode, i like the tenders that are miiliamps, then you do not need to worry about overcharge.

TCH-43mpg
VW TDI--48
08 LS 600 HL-20
08 LX 470-16

Also keep in mind that the battery is located in the trunk, thereby reducing the extreme temperature swings a battery in the engine compartment will see. This should lengthen the battery life considerably. I would be supprised if the battery does not last at least 6 years, if not more. Also these batteries don't see a great deal of load. The traction batteries doo almost all that work.

There's a temperature sensor on the 12-V battery, that is used by the ECU to control the maximum charging current used, so as not to decrease the battery's life by charging it too rapidly at low temperatures.

Does anyone out there have a ScanGauge? I'm finding that my 12-V battery's voltage frequently drops below 12 V when my car is ON, but not READY. [I.e., two pushes of the Start button with your foot off the brake.] If you do have a ScanGauge, could you please read your 12-V battery's voltage under the above condition, say in the morning before you start the car after an overnight "sleep," and let me know the result? Normally, a properly charged 12-V battery's voltage should not drop below 12 V. As soon as my car is put in READY mode, my battery's voltage rises above 14 V, as should be the case. Does anyone know whether "glass separator" batteries behave differently? FYI, this is listed as a 48 amp-hour battery.

Stan

Float Step. This is a regulated voltage of not more than 13.4 volts and usually less than 1 amp of current. This in time will bring the battery to 100% charged or close to it. The float charge will not boil or heat batteries but will maintain the batteries at 100% readiness and prevent cycling during long term inactivity. Some gel cell and AGM batteries may require special settings or chargers.
AGM: The Absorbed Glass Matt construction allows the electrolyte to be suspended in close proximity with the plateÕs active material. In theory, this enhances both the discharge and recharge efficiency. Actually, the AGM batteries are a variant of Sealed VRLA batteries. Popular usage high performance engine starting, power sports, deep cycle, solar and storage battery. The AGM batteries we sell are typically good deep cycle batteries and they deliver best life performance if recharged before the battery drops below the 50 percent discharge rate. If these AGM batteries are discharged to a rate of 100 percent the cycle life will be 300 plus cycles and this is true of most AGM batteries.
100% charged=12.7 volts 75% =12.4 volts 50%=12.2 volts 25%=12 volts full discharged=11.9 volts

TCH-43mpg
VW TDI--48
08 LS 600 HL-20
08 LX 470-16

I tried mine this evening and saw a pattern which may explain what you're experiencing:

At ON (but not READY), my scangauge recorded 11.9V, i.e. below 12V as well. As a matter of fact, as soon as I depressed the brake pedal (and the power button glowed green vs. yellow, indicating "go ahead & start me up if you want"), it dropped to even 11.8V or 11.7V... I tried it a few times, same results every time.

But here's the kicker: it was evening and I have my lights set to "AUTO", so they go on as soon as the car is turned to "ON" (even if w/o brake being depressed). Once I turned that auto-setting off and repeated the same steps, I got 12.1/12.2V in "ON" mode. Read: above 12V, just as you were expecting.

I forgot to see whether depressing the brake pedal would bring it down to 12.1V or 12.0V (or lower?), but that's probably moot by now. The likely reason you probably got below 12V once in a while are your lights draining power from the battery.

Mind you, I'm not an electrician but I did stay at a Holiday Inn last night...