Losing all electrical power in a car - modern things that should not happen

[tom66]

The other week, I purchased a 2015 Volkswagen Golf GTE, a plug-in hybrid car.

Today I was driving along and the car popped up with a message, "12V battery not charging.  Car may not restart.  Visit workshop soon!"

This isn't great, but I decide to continue driving. A mile later everything dies.  Lights, instrument cluster, brake assistance,  power steering.  Everything.  At 40 mph.  And the worst part is that the electronic parking brake wouldn't engage, and I'm on a hill, so I'm left pressing the brake pedal down continuously whilst I'm completely unlit on a dark road. 

My girlfriend was sitting in the car.  Luckily, she was able to hold the brake down while I jump started the car.  After doing this,  the car drove OK. 

So, on examining the fault, when I got the car home, as soon as I turned off the ignition,  the car died immediately. All power lost.  Nothing worked any more.

I checked the battery and it was measuring just 1.8 volts.  So,  the battery has clearly failed.  Here's what gets me.  This happens on petrol cars too,  but they can continue running as long as the engine is still going.  This car cut out while driving.  Presumably the DC-DC converter in the hybrid system briefly turned off, perhaps when switching between petrol and electric, but there was no battery to "catch" it.  If the car knew the battery was potentially faulty, why did it shut down the DC-DC? 

In my mind, this shouldn't be a fault that can happen (and from reading about it, it's not uncommon on EVs and hybrids.)

[thm_w]

EV/hybrids like to run everything critical off of the 12V lead acid battery, its probably cheaper/simpler/etc. Even tesla has one: https://teslamotorsclub.com/tmc/threads/model-3-12-volt-battery-location.107340/
Seems so ridiculous that they haven't been replaced by using the main li-ion pack, which would eliminate the problem you had, but they must have their reasons.

There are *some* gas cars that will have problems when the batteries dies mid drive as well. In the future you could check the battery health more often.

[Ian.M]

You don't *know* the battery is bad though if its been discharged to 1.8V its shortened its life a lot even if you recharge it within 24H.   It could be 12V charging system failure, which is probably a buck converter off the main DC bus.

Try to recharge the 12V battery out of the car - if it holds a charge, you'll probably need to take the car to a dealer 's garage who can access the computerised diagnostics and error logs.  If it doesn't, a new battery has 50/50 odds of curing it.  If it doesn't charge the new battery, again its a job for the dealer.

[Gregg]

Tom66, did this incident happen as you drove past one of the many haunts of Lucas, Prince of Darkness? 
This sort of thing used to happen a lot with my 1957 MGA until I replaced the Lucas generator with a US alternator, replaced all of the wiring which was getting low on magic smoke, got rid of the nasty dual 6 volt battery system and installed a PerLux Hall effect module to eliminate the points in the distributor.  The only Lucas parts remaining are the starter, distributor and turn signal switch.   It has been much more reliable but the ghost of Lucas occasionally teems up with Murphy to make me question my sanity.

[grythumn]

I had this happen in an old Honda Civic Hybrid... doesn't use an alternator, and if the traction battery acts up, the DC-DC converter won't charge the 12V system.

Replaced the 12V battery to get home and then the car... wasn't worth putting a new traction battery in.

-R C

[tom66]

You don't *know* the battery is bad though if its been discharged to 1.8V its shortened its life a lot even if you recharge it within 24H.   It could be 12V charging system failure, which is probably a buck converter off the main DC bus.

Try to recharge the 12V battery out of the car - if it holds a charge, you'll probably need to take the car to a dealer 's garage who can access the computerised diagnostics and error logs.  If it doesn't, a new battery has 50/50 odds of curing it.  If it doesn't charge the new battery, again its a job for the dealer.

I know the 12V system is working fine,  as it's 14.5V when the car is on.  The problem is, as soon as the car turns off, the 12V battery isn't there to "catch" it so it dies.

In my mind if the car knows the 12V battery is poor/weak, i.e. it can display the error message,  it shouldn't switch off the 12V DC-DC leading to the car dying immediately.

[Ian.M]

That puts a slightly different light on it and a new battery will fix it, but a Lead Acid battery that's not repeatedly been run flat and has been regularly charged shouldn't have died in only 3 years.   I believe your car uses a 48V starter/generator so the 12V battery should have a fairly easy life.

I hope you are lucky and it is *just* the battery, not the charging system killing it by over-charging or other possibly software faults impacting its life, otherwise you'll find yourself replacing it again in a year or two.

[bsfeechannel]

This happens on petrol cars too,  but they can continue running as long as the engine is still going.

Not if the alternator fails and the car gives you no indication. The engine is going to run on the battery until it gets totally depleted. The engine stops and you have exactly the same situation: absolutely no power whatsoever and no way to jump start your engine.

Don't ask me how I know that.

[tom66]

This happens on petrol cars too,  but they can continue running as long as the engine is still going.

Not if the alternator fails and the car gives you no indication. The engine is going to run on the battery until it gets totally depleted. The engine stops and you have exactly the same situation: absolutely no power whatsoever and no way to jump start your engine.

Don't ask me how I know that.

Every car I've seen indicates an alternator or battery problem with the battery idiot lamp. But in any case it won't usually do it at speed. The big issue for me was this happened at 40 mph while in the third lane of a road... I had no indicators or hazard lights and had to get across the road without hitting anyone,  very difficult!

[james_s]

Those electric parking brakes are idiotic, the parking brake doubles as an emergency brake and should always be purely mechanical. This incident demonstrates precisely why the system as designed is unacceptable. What if you had been on a hill with nowhere to go and houses or a cliff or something at the bottom? You could be stuck there pressing hard on the brake until help arrives to keep from killing somebody or yourself. It's also ridiculous that a car would completely lose power so suddenly like that.

[Stray Electron]

There are *some* gas cars that will have problems when the batteries dies mid drive as well. In the future you could check the battery health more often.

  More than "some" modern gas cars have this problem!  Johnson Control bought out many of the other battery makers in the US and about ten years ago then started making really crappy batteries. I had no less than SIX of them die in various cars in less than a year and in every case the car died on the spot.  With normal aging a battery will fail to crank the engine but if they car is running it will keep running but the Johnson Control batteries just dead shorted when they failed. Every case case the battery was less than one month old, two of them failed the same day that I bought them!   Now I check every battery that I buy, regardless of brand name, before I buy it and I will NOT buy another battery made by Johnson Control. 

[Wilksey]

This happened to me in an old Ford (early 90's Fiesta), just cut out whilst driving, no electrics, happened to roll to a stop at a set of traffic lights, people blaring their horns and shouting at me to put my hazards on if I have broken down  , and I must have lost my voice shouting back "it's a bit hard to do with no f**king battery you thick c**t", I wasn't very happy and wasn't up for being shouted at.

Trouble is, everything relies on electrics, if you've lost your power source you're buggered!

[james_s]

  More than "some" modern gas cars have this problem!  Johnson Control bought out many of the other battery makers in the US and about ten years ago then started making really crappy batteries. I had no less than SIX of them die in various cars in less than a year and in every case the car died on the spot.  With normal aging a battery will fail to crank the engine but if they car is running it will keep running but the Johnson Control batteries just dead shorted when they failed. Every case case the battery was less than one month old, two of them failed the same day that I bought them!   Now I check every battery that I buy, regardless of brand name, before I buy it and I will NOT buy another battery made by Johnson Control.

I had a battery fail like that last year too. One day it was fine, the next morning I got in my car to go to work, turned the key and everything went dead. I didn't tear apart the battery to investigate but an internal connection must have opened up like a fuse. I don't know anymore who made it as it's long gone but it was the only time I've ever had one fail so suddenly. It showed no signs of impending failure prior to that morning.

[KL27x]

I know the 12V system is working fine,  as it's 14.5V when the car is on.

Not necessarily. I had a motorcycle with a strange battery problem. The 14.5V looked fine. Replaced the battery, and it died, again. The voltage regulator was getting too hot. So you could ride it around, stop at your destination, then ride it back home, no problem. But if you made a quick stop, say for gas, and restarted the engine WHILE the regulator was nice and toasty, the engine would start and run fine, but the regulator would not be work. The 14.5V rail would then sag to whatever the battery could put out, and the battery would eventually die and not be able to restart. Fan on regulator fixed the problem.

[james_s]

That doesn't really seem like a fix, more like a band aid. I'd be worried that whatever fault it had would get worse.

[KL27x]

The info on the model suggested that the regulator is destined to fail after a few years. It's a common problem on that type of motorcycle, esp if you live in a climate with dry heat. The regulator was bolted to a piece of the cast aluminum frame under the fairing. At low vehicular speed, there is no air flow. I figured I'd see if the fan worked before putting on the new (non OEM) regulator; there was enough room to put a big cpu fan in there to cool the regulator and surrounding frame. The fan ran whenever the electrical was on. Worked for many years just fine. I never installed the new regulator. I had installed a panel voltmeter to diagnose the problem, and I just left it in there; so I would know if there was a problem that might damage the new battery, and as long as I had a charged battery, I wouldn't be stranded anywhere. The thing worked 100%.

IMO, the fan WAS the fix, and simply replacing the regulator would have been the bandaid. I had a great mechanic, and I'm sure he would have replaced the regulator and the battery. And I'd see him again in a couple years. This would have paled next to the confidence I had knowing how and when the regulator would fail, if the fan didn't keep it happy.  And watching it work for years with zero trouble.

[bsfeechannel]

Every car I've seen indicates an alternator or battery problem with the battery idiot lamp. But in any case it won't usually do it at speed.

That's what I thought, until I tore down an alternator. With some of them the "idiot" lamp detects only one of the phases. If one of the diodes of the rectifier gets bust and it happens to be the one that is not being sensed, the "idiot" lamp (I love the name) won't tell you that there is a problem.

The big issue for me was this happened at 40 mph while in the third lane of a road... I had no indicators or hazard lights and had to get across the road without hitting anyone,  very difficult!

I was a bit luckier. I was going for a job interview. The car went dead a few blocks from my appointment. I left the car parked on a quiet street and walked the rest of the way. After the interview, I called up the insurance company. They sent me a repair guy with a new battery. It was enough to start the engine and drive to an auto repair shop.

From that day on, I lost my faith in alternators. I always check if they're really working by measuring their output voltage before a long trip.

[CJay]

The other week, I purchased a 2015 Volkswagen Golf GTE, a plug-in hybrid car.

Today I was driving along and the car popped up with a message, "12V battery not charging.  Car may not restart.  Visit workshop soon!"

This isn't great, but I decide to continue driving. A mile later everything dies.  Lights, instrument cluster, brake assistance,  power steering.  Everything.  At 40 mph.  And the worst part is that the electronic parking brake wouldn't engage, and I'm on a hill, so I'm left pressing the brake pedal down continuously whilst I'm completely unlit on a dark road. 

My girlfriend was sitting in the car.  Luckily, she was able to hold the brake down while I jump started the car.  After doing this,  the car drove OK. 

So, on examining the fault, when I got the car home, as soon as I turned off the ignition,  the car died immediately. All power lost.  Nothing worked any more.

I checked the battery and it was measuring just 1.8 volts.  So,  the battery has clearly failed.  Here's what gets me.  This happens on petrol cars too,  but they can continue running as long as the engine is still going.  This car cut out while driving.  Presumably the DC-DC converter in the hybrid system briefly turned off, perhaps when switching between petrol and electric, but there was no battery to "catch" it.  If the car knew the battery was potentially faulty, why did it shut down the DC-DC? 

In my mind, this shouldn't be a fault that can happen (and from reading about it, it's not uncommon on EVs and hybrids.)

I've had the same error message on my partner's 2017 Sharan, it's not a hybrid or EV, it's a diesel, fortunately it was parked and the brake was already engaged.

[james_s]

Both of my cars have proper volt meters in the dash as factory options, it's something that is conspicuously absent from most modern cars.

[tom66]

Those electric parking brakes are idiotic, the parking brake doubles as an emergency brake and should always be purely mechanical. This incident demonstrates precisely why the system as designed is unacceptable. What if you had been on a hill with nowhere to go and houses or a cliff or something at the bottom? You could be stuck there pressing hard on the brake until help arrives to keep from killing somebody or yourself. It's also ridiculous that a car would completely lose power so suddenly like that.

I eventually figured out that you can shift the gearbox into Park without power so this is your parking brake.  It is not great for the gearbox but it could be used in a pinch.  But I agree, the EPB should have a battery backup, or some mechanical override.  (And I suppose a manual car could be left in gear to accomplish the same thing - though less confident in this!)

Both of my cars have proper volt meters in the dash as factory options, it's something that is conspicuously absent from most modern cars.

My car has a way to show the 12V on the display, in a factory service menu.  Point is it wouldn't have worked because the car's "alternator" (DC-DC system) was working fine,  the battery just wasn't there.  As soon as the car briefly turned off the DC-DC (I'm not sure why, but may have been a glitch) the car died.  That meter wouldn't have told me anything.

[eugenenine]

Those electric parking brakes are idiotic, the parking brake doubles as an emergency brake and should always be purely mechanical. This incident demonstrates precisely why the system as designed is unacceptable. What if you had been on a hill with nowhere to go and houses or a cliff or something at the bottom? You could be stuck there pressing hard on the brake until help arrives to keep from killing somebody or yourself. It's also ridiculous that a car would completely lose power so suddenly like that.

The car manufacturers are very careful to make sure those are only called parking brakes and never emergency brakes so to deflect any liability should someone use them in an emergency.  They haven't been called emergency brakes in decades.

[eugenenine]

A plain old DC voltmenter can't tell everything.  I'm fighting an issue now where I have to take my battery back to NAPA every 6 months for a warranty replacement.  I drove over one day after jump starting and they hooked up their tool and said everything looks fine.  But yet if I don't drive anywhere on the weekend by Monday the battery is too low to start.  I started researching and found that if you have AC on top of the DC 14v charging then the alternator has a bad diode.  I have 2v AC on mine.  So what I've figured out now is that the bad diode in the alternator is draining the battery.  So for the last 5 days I've been unhooking the battery and reconnecting it each time I drive anywhere.  Yet the engine computer, dash volt meter and the additional voltmeter I added all show good.

Now my problem is I can't buy the diode pack anywhere, only a remanufactured alternator for $150.

[CJay]

I'vwe not stripped an alternator for many years now, are they still using press fitted stud diodes?

[james_s]

My car has a way to show the 12V on the display, in a factory service menu.  Point is it wouldn't have worked because the car's "alternator" (DC-DC system) was working fine,  the battery just wasn't there.  As soon as the car briefly turned off the DC-DC (I'm not sure why, but may have been a glitch) the car died.  That meter wouldn't have told me anything.

I can get an idea of battery condition by watching the voltmeter. A battery that is in poor shape is quite low when I turn the key on in the morning and sags further when cranking the engine, then quickly shoots up toward the high end of the scale once the engine starts. A healthier battery is higher to begin with and rises more slowly as the battery fully charges. It will also vary less when accessories like headlights are switched off and on. Nothing beats real analog gauges.

[eugenenine]

I'vwe not stripped an alternator for many years now, are they still using press fitted stud diodes?

I've not taken one apart in years either.  All the auto parts stores just list remanufacturerd alternators and no individual parts.