Technical Car has trouble starting after battery drain

[Codebreaker]

After doing some small electrical work (hard wiring phone charger and a dashcam) I could't start the car. I tried it a couple of times with relays clicking and light flickering all over the place so I gave up and decided to check voltage of the car battery which it turns out was 10.3V so I jump-started it with another car, at which time the light for checking glow plugs turned on.

After that, sometimes when starting a car that has been sitting overnight (0-5°C night temperature), I have to crank the car two or tree times for it to tun on. Checking the battery voltage after sitting there overnight it's reading 11.5V. I've been driving the car for total 9h total since the battery drain so I'm assuming that's enough for the alternator to charge the battery (VARTA C30 54Ah 530A) to its full potential (get it? potential? I'll see my self out...). When the car is running and the alternator is charging the battery the voltage is 14.6V. Checking this table that I've found it seams that my battery can't hold a charge and is good as gone. Is that true and should I run to the store right away?

Additionally, before I did any work, there were times when the car couldn't turn on after the key was in MAR position for longer period of time (30 or more seconds). Could that indicate a bad battery?

Given what I just said, could glow plugs actually be ok and its the battery not giving enough energy to the glow plugs thus giving off the warning?
Or is it the other way around and the 11.5V is actually ok for this battery and it's the glow plugs that are causing the starting issue?

Of course I could replace both the car battery and the glow plugs but I want to check here before having to go outside in the cold.

 

[portland_bill]

The battery is dead.
Might be just age, or fairly old and gave up after you discharged it, as the last straw.
If it was below 12.3v for more than a day, it will have killed it. If it was already weak, dropping it down for just a few hours will cause it to give up.
Look at Tayna batteries. Good prices, quick delivery.

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[Codebreaker]

Just a report on my situation. I'm an idiot (probably). I bought the new battery. The voltage now showed 11.8V. I was perplexed why it was still under 12V. Then it finally hit me - the glow plugs must draw a larger current. My current-clamp does not measure DC so a blown fuse in my multimeter later, I found out that the glow plugs draw more or equal to 10A. If I let the car sit there for a few more seconds before I turn on the car, the current drops to 2A and battery goes back to exactly 12V (with the lights, radio and fans off). Soooo yeah. The battery was probably still good enough (since I measured voltage after key to MAR position with the new phone charger that has a voltage reading). I can't test it since I gave it to the battery dealer for a rebate. I can't find any graphs that shows voltage-current characteristic of a lead-acid battery so I can compare how the battery should perform. But here are my measurements with the new battery:

Car off, key out - 12.6V - ~0.02A
Key to MAR position with glow plugs active - 11.8V - ~12A
Key to MAR position with glow plugs inactive - 12V - ~2A

I hope this is how it should be since it is a new battery.

The glow plug warning light still comes on so - on the next episode of codebreaker tragedies - changing glow plugs.

 

[jackwhoo]

Just a report on my situation. I'm an idiot (probably). I bought the new battery. The voltage now showed 11.8V. I was perplexed why it was still under 12V. Then it finally hit me - the glow plugs must draw a larger current. My current-clamp does not measure DC so a blown fuse in my multimeter later, I found out that the glow plugs draw more or equal to 10A. If I let the car sit there for a few more seconds before I turn on the car, the current drops to 2A and battery goes back to exactly 12V (with the lights, radio and fans off). Soooo yeah. The battery was probably still good enough (since I measured voltage after key to MAR position with the new phone charger that has a voltage reading). I can't test it since I gave it to the battery dealer for a rebate. I can't find any graphs that shows voltage-current characteristic of a lead-acid battery so I can compare how the battery should perform. But here are my measurements with the new battery:

Car off, key out - 12.6V - ~0.02A
Key to MAR position with glow plugs active - 11.8V - ~12A
Key to MAR position with glow plugs inactive - 12V - ~2A

I hope this is how it should be since it is a new battery.

The glow plug warning light still comes on so - on the next episode of codebreaker tragedies -

Hi,

Glow plug light should come on at key on, wait for it to go out before cranking engine.
Is the glow plug light coming back on after engine starts?
Which engine is it?

You can check the continuity of each glow plug to track down which has failed.

Read up on replacing glow plugs before attempting to remove any glow plug , you may decide not to try.


Good luck

J

 

[Codebreaker]

@jackwhoo Yes the light comes on after engine start. Its a diesel 1.3 Multijet 55 kW

According to this guide it does not seem hard to replace.

 

[chris3234]

Just a report on my situation. I'm an idiot (probably). I bought the new battery. The voltage now showed 11.8V. I was perplexed why it was still under 12V. Then it finally hit me - the glow plugs must draw a larger current. My current-clamp does not measure DC so a blown fuse in my multimeter later, I found out that the glow plugs draw more or equal to 10A. If I let the car sit there for a few more seconds before I turn on the car, the current drops to 2A and battery goes back to exactly 12V (with the lights, radio and fans off). Soooo yeah. The battery was probably still good enough (since I measured voltage after key to MAR position with the new phone charger that has a voltage reading). I can't test it since I gave it to the battery dealer for a rebate. I can't find any graphs that shows voltage-current characteristic of a lead-acid battery so I can compare how the battery should perform. But here are my measurements with the new battery:

Car off, key out - 12.6V - ~0.02A
Key to MAR position with glow plugs active - 11.8V - ~12A
Key to MAR position with glow plugs inactive - 12V - ~2A

I hope this is how it should be since it is a new battery.

The glow plug warning light still comes on so - on the next episode of codebreaker tragedies - changing glow plugs.

12v exactly is still quite low for. Anew battery it doesn't seem fully charged at that

 

[portland_bill]

@jackwhoo Yes the light comes on after engine start. Its a diesel 1.3 Multijet 55 kW

According to this guide it does not seem hard to replace.

The glowplugs, on these and many engines, have a habit of corroding into the head, making them very difficult to replace. It is easy to apply too much pressure when trying to remove them, and break them off. Options then are either to remove the head or get a specialist to remove them, there are a few who are mobile. By all means try, but be careful, and if they resist, best to stop before breaking them and seek professional help.