Car lost all electric power, went dead on road

[Helihover]

This is weird. The X should have stayed running. I understand everything is dead when the engine is off and battery is disconnected.

Here's a guess on what happened. Look at the battery as a resivor of availible amps. The alternator of course is the charger replacing amps to the battery. I believe TerminatorX you said you were accelerating at the time to change lanes or something like that. Mabey the demand for amps, for ignition purposes, was higher than the output of the alternator. That's some serious amp pullin though. Anyone one know the amperage demand at a particular rpm?

[TerminatorX5]

hmmm... so, you think the car was running on alt already, while the battery was disconnected, and higher demand put additional stress on charging system, that collapsed? interesting... that might be a feasible explanation...

[Helihover]

Originally Posted by TerminatorX5

hmmm... so, you think the car was running on alt already, while the battery was disconnected, and higher demand put additional stress on charging system, that collapsed? interesting... that might be a feasible explanation...

Yes. The easy way to find out would be to fire up the X, get out, and then go hit your disconnect switch.

If still running, you could then rev it and see what happens or go drive it....

[TerminatorX5]

Originally Posted by Helihover

Yes. The easy way to find out would be to fire up the X, get out, and then go hit your disconnect switch.

If still running, you could then rev it and see what happens or go drive it....

tempting...


but i am not sure if i want to play dead on purpose - what if i will not be able to revive the thing afterwards??? this is not like one of those "mission impossible" movies, when tom cruise died and had his girlfriend zap him with electricity to bring him back...

i'll think about this one...

[Helihover]

Yes indeed.

I still would like to know how many amps the electrical system pulling at say, 1k rpms and 5k rpms.

The alternator is rated at what, 140 amps? Why with all the technology and fail safes, ect would BMW design a vehicle that could pull more amps than the alternator was producing? Or is your alternator on the way out?

[TerminatorX5]

the alt is rated at 170 or 180... the biggest fuse in the car is 200 Amps... as far as i can tell, the alt is still going strong but who knows - it may just fall off a cliff and not decline slowly...

when i do my upgrades or additions, i mind the total system limitations on the total amperage and monitor the gauges of the wires used and the inline fuses that i use... I am not maxing out my alt output potential nor the battery wattage...

the total draw of all my additional gadgets at this moment stands at about 2-3 amps additional, which is about 1-2% of the total system capacity... the car has heated seats at all 4 corners, when all 4 seats are and the heated steering wheel are on, those alone draw tens of amps... and the car was designed to keep up with it... so my couple amps running is not much of a burden...

I just think that the battery stays constantly in the electricity loop, even when the car is fed off an alternator - the flow of charging juice is going to the battery, as the voltage regulator is keeping the voltage above 12 V nominal and the while the alt is running, the battery is not supplying additional amperage...

the alternator capacity is 170A (some sources say - 180A). the voltage regulator must provide at least 13V, thus the alternator is rated at 2210 Watts (or 2340 W if it is 180A). the battery is rated at 12V and with 200 A fuse (which is probably industry standard 110% of system capacity), the maximum sustained current is 181 A which is inline with the alt capacity.

the regulator supplies 13V (varying with engine speed but not exceed 14 V nominal) under different load demands, meaning, if the car demands 25 amps from alt, it will keep 13 volts and provide 25 amps... next second demand spikes to 70Amps, the regulator MUST sustain 13 volts and supply 70amps... that is the beauty of the regulator, it must keep one parameter, in this case, the voltage at nominal (13V) level, while the demand for amps varying with changing loads... once the car demands more than 180 amps, say, 198 amps (to keep below 200A fuse rating), the voltage will drop below 13 volts as the alternator can NOT exceed its wattage rating (in our case it will be 2210 W / 198A = 11.2V or 2340 W / 198A = 11.8 V)... all numbers are nominal, meaning that the the battery itself might not be 12 V, the alternator can put out from 12.5 to 15V (16V considered deadly for electronics), the alternator has internal lag, which is the response time needed for the electronics to level the voltage if there is spike in the demand, during which time the voltage can drop down from nominal, and when the demand is gone, because of the lag the voltage can spike...

didn't mean to do electrics 101 here... lol...

[Helihover]

It's all good. I would consider myself up to par on the basics of batteries, amps, and chargers. I also tend to look at things in a less complex matter. Like a battery being the resivor of the electrical system and amps being the "fuel" for the electrical system. The amount of amps the battery is capable of holding would be like the size of your "gas tank" for the electrical system. The alternator being the Unical 76 gas station

So do you think you had a spike when you punched it that caused the X to shut down?

Anyone else wanna chime in? I'm really curious as to what happened.

[flg8r90]

Originally Posted by TerminatorX5

tempting...


but i am not sure if i want to play dead on purpose - what if i will not be able to revive the thing afterwards??? this is not like one of those "mission impossible" movies, when tom cruise died and had his girlfriend zap him with electricity to bring him back...

i'll think about this one...

Been away for a few days. Glad to hear your family is safe.

Your better off "playing dead" and have it die under a controlled situation. I'd hate to have it happen during a left turn with on coming traffic. (KNOCK ON WOOD !!)

[TerminatorX5]

connected the car to INPA, read all modules, all error codes, the shadow memory... nothing significant - no power spikes from the alt, no dips...

however, i think i found a victim of the incident - the rain sensor... it is not coming online, and the headlights turn on with a 3 second delay - i turn the engine on, and the lights turn on 3 seconds later, both the exteriors and the illumination inside... the light still come on... the vertical adjustment is working but the horizontal adjustment was not working... so, i thought the AHL module, the adaptive headlights is fried...

put that module in manual mode, the lights adjust left and right... but not automatic...

since i ran out of time, i did not do further troubleshooting but on my list is to check the rain/light sensor fuses, check other fuses related to the LCM and most importantly, read the saved PDFs of the errors that i pulled - i just skimmed through them...

other than that, the lighting operates as designed minus the adaptive portion. wasn't raining today, did not test the auto wipers function and was too lazy to pour bottle of water over the windshield... lol... too cold...

[TerminatorX5]

found fuse 41 (rain sensor, 5A) blown... replaced... now off to read the saved PDFs of the error memory "printouts" to see if I can dig anything else