Micro-CAN amperage draw ?

Hi,


Few days ago my car won't ignite, the electric starter and OBD light appeared good but two days after the light showed that the battery was nearly down.

Today I've seen my Micro can with its light and I tilted " thats probably it the guilty "

So what kind of amp draw does the Micro can consume ?

it is plugged in all the time since nearly 9 mounth.


Thanks by advance

benTSH said:

So what kind of amp draw does the Micro can consume ?

Click to expand...

About 70 mA when idle and powered only from the "car" (so not plugged into any USB power).

How long was the car sitting unused with the Micro-CAN plugged in?

-Uwe-

from the Sunday evening ( around 9 pm ) to the next wednesday morning ( 10 am )

I always never let my PC on the car, only the Micro-can is plugged in permanently.

VW guys told me that the Max amperage for Battery life is around 100 mA so I've probably made a mistake Leaving connected the Micro-can

Your typical VW dealer employee barely graduated high school. By that logic the starter, pulling several hundred amps, would instantly destroy your battery :-) It's a function of draw over time, ie Amp*Hours. Typical car batteries are 70Ah to 110Ah. You've pulled less than 3 days times 24 hours times 0.07A= 5 Ah out of your 70-110Ah battery by leaving the micro-CAN plugged in. Insignificant.

The question is in what condition the battery? How old is, how much is charged etc...

2 yo and a half

Out of warranty? If the condition tested with suitable device? Charger used...

benTSH said:

from the Sunday evening ( around 9 pm ) to the next wednesday morning ( 10 am )
I always never let my PC on the car, only the Micro-can is plugged in permanently.

Click to expand...

So 2-1/2 days. It might have pulled a total of ~4.5 Amp-Hours from your battery during that time. That should not be enough to have any real effect on the battery.

-Uwe-

Well I'm agree that the 2 days 1/2 are not enought but probably the 9 mounthes have decreased little bit amp by little bit because it is 455A after 9 mounthes and maybe the vag-com plus each ingnitions are too much for the alternator and a Dynaudio 600W pack .

I've check that I have 14.2V so it works good but it is better to disconnect the vag-com IMHO.

And now I'm going to see because I still use the same battery ( warranty of 2 years ... ) which was not totally dead as it started the starter, after the help of a booster one time yesterday I'have start the engine perfectly around 6 times so it seems to regenerate and not I 'm going to disconnect the vagcom each time.

Yup, the above is assuming you have a net daily positive Amp balance by driving the car long enough every day. If it was already borderline, the micro can could certainly be the tipping point over 9 months. Then again we're seeing batteries fail every two years in Tiguans here :-)

Eric said:

Then again we're seeing batteries fail every two years in Tiguans here :-)

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I'm only aware of one particular Tiguan that's had that problem.

-Uwe-

hmm........... OK going back to basic electricity 101 - If the current draw is 100 mA and if this is applied to Eric's 70 Amp hour battery (using his lower battery rating - to be conservative) and we assume a fully functioning and fully charged battery, then the theoretical time to flatten the battery is 70/0.1 =700 hrs, or 29 days (assuming no other load is taken from the battery during the period).

But aren't we "straining gnats and passing elephants" here in focussing on the 100 mA? Rather than looking-at the quiescent current of the Micro-CAN cable being the culprit, couldn't the continuous presence of the Micro-CAN cable plugged into the OBD port have the effect of stopping the control modules from going to sleep when they would otherwise do? Depending on the state in which the diagnostic cable was left - Could it not be this effect (i.e. keeping the modules awake as well as their associated transducers and sensors) that is the larger problem for battery drain?

Don

DV52 said:

But aren't we "straining gnats and passing elephants" here in focussing on the 100 mA? Rather than looking-at the quiescent current of the Micro-CAN cable being the culprit, couldn't the continuous presence of the Micro-CAN cable plugged into the OBD port have the effect of stopping the control modules from going to sleep when they would otherwise do? Depending on the state in which the diagnostic cable was left - Could it not be this effect (i.e. keeping the modules awake as well as their associated transducers and sensors) that is the larger problem for battery drain?

Click to expand...

I don't think so. Sitting there, just plugged in, the Micro-CAN shouldn't be putting any traffic on the bus at all, and without it generating some kind of messages, I can't see any reason why the modules in the car wouldn't go to sleep as usual just because the device is plugged in.

-Uwe-

...this being the only Auto-Scan of yours I can find...

http://forums.ross-tech.com/showthr...t-in-compression&p=57978&viewfull=1#post57978

...I can see at least 2 possible causes for your quiescent current problems. That is, assuming this is the car we're talking about. A decent start for some true diagnostics would be a fresh Auto-Scan, ideally with an English version of VCDS.

that's my car; I'll do a new scan tomorrow but last week I made one but I there is not anything new

Uwe said:

I don't think so. Sitting there, just plugged in, the Micro-CAN shouldn't be putting any traffic on the bus at all, and without it generating some kind of messages, I can't see any reason why the modules in the car wouldn't go to sleep as usual just because the device is plugged in.

-Uwe-

Click to expand...

Uwe_ My hypothesis was predicated on the statement "Depending on the state in which the diagnostic cable was left "

I think that I can see that a cable simply plugged onto the OBD port (and doing nothing) wouldn't have an "oxycodone" effect on the other control modules. But is this still the same if the software wasn't exited properly? Or is this just so low a probability as to be trivial?

Don

DV52 said:

I think that I can see that a cable simply plugged onto the OBD port (and doing nothing) wouldn't have an "oxycodone" effect on the other control modules. But is this still the same if the software wasn't exited properly?

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I believe so, yes. The Micro-CAN doesn't have any functionality in it to keep a diagnostic session alive on its own; that's all handled by the software with that generation of interfaces.

Now there have been cases in the distant past where control modules did not end a diagnostic session themselves if they were not explicitly told to, which kept them from going to sleep and thus caused them to consume excessive amounts of current with the car parked, but this was acknowledged as a bug by VW. In that case it didn't matter whether the diagnostic tool/cable was left plugged in or not, it was simply a question of whether the session had been properly closed by the tool.

Anyway, I can't see a causal relationship between leaving the Micro-CAN plugged in for a couple of days and a dead battery, at least not without a computer running VCDS on the other end of the Micro-CAN keeping a session alive. I'll note this is not the case with the HEX-NET, which obviously does have the capability to keep sessions alive without the help of a PC.

-Uwe-

^^^^ OK - I guess then as your President elect has famously said I'm........

I left my old KII-USB plugged in for 24 hours before and car was flat, wouldnt start