HybridFan — Thank you for trying to make the battery voltage measurements I requested. One of the reasons why I started monitoring my TCH's 12-V battery voltage was that I had been experiencing the same "Connecting ..." issue with my ScanGaugeII that you have now reported! When I told Ron DeLong of Linear-Logic (the manufacturer) about this, he suggested that I was suffering from a momentary 12-V battery "brown-out" (drop in voltage) that misled ScanGaugeII into thinking that it had been disconnected — hence its attempt to re-Connect. I had been trying to see if I indeed had a brown-out problem by monitoring the TCH battery's voltage. I had seen no substantial voltage drops occurring, however, and so had told Ron that I could see no evidence of a brown-out. Ron was coming to the conclusion that my ScanGauge (or TCH!) might be behaving abnormally, when you reported the same issue with your ScanGauge yesterday!

Here's what I have learned from Ron and from my own investigations so far:

1. ScanGaugeII will try re-Connecting if it sees the battery voltage dropping below 3 V for more than 100 ms. It will interpret this as a disconnection, requiring it to try Connecting again. I've never seen such a low battery voltage, and I'm sure this isn't happening.

2. ScanGaugeII wakes up when it sees a voltage rise of at least 300 mV over a 1.3 s period. This occurs when the TCH is switched from OFF, ACC, or ON to READY. The voltage then rises to 14.2 V as the NiMH battery starts charging the 12-V battery through the dc-to-dc converter.

3. When "on" with its LCD display on "White" and "High," ScanGaugeII draws a current of ~100 mA from the 12-V battery. When sleeping, it still draws a current of ~40 mA from the OBDII port (which is permanently powered). [Incidentally, this residual drain will consume ~1 Ah of charge every day. The 12-V battery is a 48 Ah unit, and this drain would discharge it over a period of a month or more. So, ScanGauge should be disconnected if the car is to be unused for more than a few weeks. I can now confirm that the 12-V battery is an AGM type — see page 4 of TSB PD020-06 posted to this group by schmidtj.]

4. If I make sure that my ScanGaugeII is showing the Gauges screen with VLT displayed when I switch my TCH OFF, then I can usually (but not always) wake it up by pressing its Home button without triggering the "Connecting ..." problem. It will then display the current battery voltage even with the car OFF, and then go back to sleep. I think you must be on this Gauge display screen when switching OFF for this to work — I don't think you can change the display without triggering the "Connecting ..." problem. This may be why you couldn't make the measurements with the car OFF.

HybridFan, can I trouble you to try this and see if it works for you too? Thanks! If so, you should also succeed in making an early-morning measurement with your TCH OFF, and disturbed no more than by opening its door. Let me know what happens. I would like to suggest that you also drop Ron DeLong an e-mail at ron.delong@linear-logic.com and let him know that you're having the same "Connecting ..." problem as I'm finding, and that you also have a TCH. It looks to me more likely to be a ScanGaugeII programming issue than a TCH battery problem. That said, however, I'm still puzzled by the battery's low voltage readings after standing for many hours. It's almost as if the battery is draining significantly while the car is OFF. I'm currently attempting to make some readings, using a current probe, to see what the standby current is from the 12-V battery when my TCH is OFF. I'll report back on what I find.

Stan