Interesting, maybe, Scangauge power use

[booster]

I would certainly think that it would do the same thing if the battery were killed in some other way like leaving the lights on, and that could turn out bad, as was said, because you would charge and go dead again repeatedly because of the Scangauge, even on a new battery, maybe wrecking it. I don't know what voltage it would have to drop to, but I did have an alligator clip jumper with a loose connection and that dropped it enough to make it completely off/on cycling, just as the radio also did. Most of this kind of stuff is all done by about 9-10 volts from what I have seen on other items.


An on/off switch would not work well, I think, in the current configuration because it compiles daily trip, yesterday trip, tank mileage, average speed type stuff that require it to have continuous clock functions.



All it really needs to do is limit the time it will try to connect at power up, and shut itself down, with a code, if it goes to long. Not rocket science.

[cruising7388]

Originally Posted by booster

An on/off switch would not work well, I think, in the current configuration because it compiles daily trip, yesterday trip, tank mileage, average speed type stuff that require it to have continuous clock functions.



All it really needs to do is limit the time it will try to connect at power up, and shut itself down, with a code, if it goes to long. Not rocket science.

As you indicate, having the Scangauge shut down after multiple failures to connect wouldn't be difficult. But, similar to a BMS wouldn't powering it back up be more complicated? With the path broken between gauge and the OBD II power terminal, absent some manual reconnect, how will the gauge be capable of coming out of its coma?

To preclude the periodic loss of data, perhaps the the manual switch shouldn't be able to power down but would serve as a reset that reconnects the comatose gauge to the OBD II power terminal. I don't see any way the gauge could otherwise reconnect on its own initiative without some periodic interrogation feature which would consume power.

[avanti]

The Canbus protocol has a "wake up" feature, so it could be done. Many devices on the Sprinter slumber until you open the door, and then immediately wake up. The proper fix is to use this feature after an initial attempt to connect on plug-in. However, the Canbus chip they use in the ScanGuage may or may not support this feature.

[cruising7388]

Originally Posted by avanti

The Canbus protocol has a "wake up" feature, so it could be done. Many devices on the Sprinter slumber until you open the door, and then immediately wake up. The proper fix is to use this feature after an initial attempt to connect on plug-in. However, the Canbus chip they use in the ScanGuage may or may not support this feature.

No argument regarding the proliferation of wake up features. But I think that any device fully disconnected from its power source is incapable of waking up on its own initiative or if it can it's because it has an internal supply or is manually reconnected. Try wiring the coil of a battery disconnect switch to the battery that's being disconnected. I've been through that exasperating drill.

[avanti]

Originally Posted by cruising7388

No argument regarding the proliferation of wake up features. But I think that any device fully disconnected from its power source is incapable of waking up on its own initiative or if it can it's because it has an internal supply or is manually reconnected. Try wiring the coil of a battery disconnect switch to the battery that's being disconnected. I've been through that exasperating drill.

Oh, that is certainly true. You can't make the parasitic draw go to zero without a physical switch. But, modern chips can make the standby impedance very, very high thus making the standby current very, very low. The chipmakers have gotten incredibly good at this in their quest to make your cell-phone battery last longer. There is no reason why the ScanGauge in "standby" has to take any more current than any of dozens of other ECUs in a modern vehicle. But it DOES take special hardware, which as I say the ScanGauge may not have.

[cruising7388]

Originally Posted by avanti

Oh, that is certainly true. You can't make the parasitic draw go to zero without a physical switch. But, modern chips can make the standby impedance very, very high thus making the standby current very, very low. The chipmakers have gotten incredibly good at this in their quest to make your cell-phone battery last longer. There is no reason why the ScanGauge in "standby" has to take any more current than any of dozens of other ECUs in a modern vehicle. But it DOES take special hardware, which as I say the ScanGauge may not have.

Point taken, particularly if the parasitic approaches the level of the local discharge of the battery itself.

My guess is that the Scangauge designers did not consider that the power terminal on the OBD II receptacle looked directly at battery rather than at ignition/start-run. Wiring it this way seems purposeless on first impression but perhaps the designers of OBD II did this to facilitate lift off for code reading devices that might not have an internal battery of its own, like the Scangauge!.

BTW, I think that in certain respects the cost effectiveness of this device is diminishing because if all you're interested in is error code reading, you can buy a basic reader for less than 35 bucks. And most of the trip information, at least on our 2017 Chevy, is available by punching buttons on the steering wheel. But that said, the awesome redeeming virtue of the Scangauge is the ability to read transmission temperatures without installing a lot of plumbing and help avoid tranny overheating damage that's expensive to repair.

[DAWg134]

Modern vehicles contain a multitude of microprocessors controlling a variety of functions. Normally, when you exit a vehicle and lock it, the system goes through a shutdown process in which the majority of processors either turn off entirely or else go into "sleep" mode.

I have seen instances wherein an improperly latched (albeit fully locked) door prevented completion of the shutdown process and the resultant current draw was in excess of 1.5 amperes instead of the normal 45 milliamperes. It is possible that the presence of the ScanGauge is preventing a full system shutdown.

Possibly, there is another reason such as a door that should've been slammed shut and wasn't and that is what is actually preventing the shutdown and also allowing the ScanGauge to continue drawing current. In other words, if the door/hood had been properly closed, then the system would've cut power to the OBDII port. In this scenario, the ScanGauge represents a symptom, not a cause.

[cruising7388]

Originally Posted by DAWg134

Modern vehicles contain a multitude of microprocessors controlling a variety of functions. Normally, when you exit a vehicle and lock it, the system goes through a shutdown process in which the majority of processors either turn off entirely or else go into "sleep" mode.

I have seen instances wherein an improperly latched (albeit fully locked) door prevented completion of the shutdown process and the resultant current draw was in excess of 1.5 amperes instead of the normal 45 milliamperes. It is possible that the presence of the ScanGauge is preventing a full system shutdown.

Possibly, there is another reason such as a door that should've been slammed shut and wasn't and that is what is actually preventing the shutdown and also allowing the ScanGauge to continue drawing current. In other words, if the door/hood had been properly closed, then the system would've cut power to the OBDII port. In this scenario, the ScanGauge represents a symptom, not a cause.

You're spot on regarding battery drain from leaving a vehicle door open. The only visible symptom is an alert LED which would consume only about 15 milliamps but the actual drain is substantially more than that and from the tests I did, seems to vary from 500ma to 750ma depending on whether it's a door or the trunk that's not completely closed.

However, I don't think the Scangauge scenario you describe is related to an open door because the OBD II power terminal appears hot even if ignition is off. In this condition a typical code reader will tell the user that no data is available and after an unsuccessful attempt to read data, I don't think it makes further attempts to read. Consequently the battery drain load is probably limited to the code reader static display but at that point, the code reader is typically pulled from the OBD II port. But when the permanently connected Scanguage fails to connect, it just keeps trying until battery voltage will no longer support it but at that point, the damage has been done.

[booster]

Originally Posted by DAWg134

Modern vehicles contain a multitude of microprocessors controlling a variety of functions. Normally, when you exit a vehicle and lock it, the system goes through a shutdown process in which the majority of processors either turn off entirely or else go into "sleep" mode.

I have seen instances wherein an improperly latched (albeit fully locked) door prevented completion of the shutdown process and the resultant current draw was in excess of 1.5 amperes instead of the normal 45 milliamperes. It is possible that the presence of the ScanGauge is preventing a full system shutdown.

Possibly, there is another reason such as a door that should've been slammed shut and wasn't and that is what is actually preventing the shutdown and also allowing the ScanGauge to continue drawing current. In other words, if the door/hood had been properly closed, then the system would've cut power to the OBDII port. In this scenario, the ScanGauge represents a symptom, not a cause.

In the case of the Scangauge, I don't think the shutdown timers like for doors/dome lights, radio, etc were causing any of it, but would react to the Scangauge going on and off trying to connect by tying to go on themselves from the induced voltage change. I could easily see the timers working, and also knew the van uses right about at .035amps parasitic. It could be sitting at .035 amps, doors closed, Scangauge plugged in and connected from previous use, and I could disconnect the battery without opening any door at all, reconnect it, and the Scangauge would go into perpetual trying to connect, using about 1.3amps. It was also exactly the same if I tested with the doors open or closed, or if I just unplugged and replugged the Scangauge. Every test I could think of all went right back to the Scanguage not connecting.

[cruising7388]

Originally Posted by booster

In the case of the Scangauge, I don't think the shutdown timers like for doors/dome lights, radio, etc were causing any of it, but would react to the Scangauge going on and off trying to connect by tying to go on themselves from the induced voltage change. I could easily see the timers working, and also knew the van uses right about at .035amps parasitic. It could be sitting at .035 amps, doors closed, Scangauge plugged in and connected from previous use, and I could disconnect the battery without opening any door at all, reconnect it, and the Scangauge would go into perpetual trying to connect, using about 1.3amps. It was also exactly the same if I tested with the doors open or closed, or if I just unplugged and replugged the Scangauge. Every test I could think of all went right back to the Scanguage not connecting.

In the current sense, the battery failure issue stems from the design of Scangauge, but in the broader sense, this problem is also a symptom reflecting that most likely some 25 years ago, the designers of the OBD II port envisaged its use as a temporary test port and didn't anticipate that future use might involve the permanent connection of devices to it.