[blitz_nomad]

Originally Posted by Neversaygbye

Nowadays I ensure that I switch off the AC and blower (in that order), audio system and lights (if on earlier) before I leave the car. You can do the same. Also, please keep a jump start cable in the car - you never know when it will be of use. I have this one in my car:

https://www.amazon.in/gp/product/B07...e?ie=UTF8&th=1

I follow a similar routine too when I leave the car - check that everything is off and dashcam is unplugged. Just that this time, since there were occupants I let the music system and blowers run. Thanks for the tip on the cable. I've decided to get the same. Do these vary depending on the car battery?

[mayankk]

Originally Posted by alphamike_1612

Couldn't the car be push started if the battery has drained? (If it's a manual)
Is there any reason why no one has suggested it?
Both the OP and a lot of the other posters who have posted their experiences also talk only about jump starting the car and not push starting it.

I believe that modern cars will not be push started if there is zero charge in the battery. Something to do with alternators, which require at least a trickle of electricity.

[Jeroen]

Originally Posted by alphamike_1612

Couldn't the car be push started if the battery has drained? (If it's a manual)

See below

Originally Posted by alphamike_1612

But, when I was a mischievous child and young adult, I have several times done the evil act of switching on the A/C when the ignition is not on and have always been treated to the wave of cold air for a full minute before some adult spots it and switches it off.
How/Why does this occur?

When the engine and AC has been running quite a lot of cold is retained in the AC evaporator. With the engine switched off and the cabin fan still running, that residual cold gets blown into the cabin. But it will only last a short time as the AC compressor is not working. Note that on many cars the AC compressor and the AC cabin fan might be switched by means of the same switch. So on the dashboard it might look as if the AC is on, but with the engine off, it will only be the cabin fan. Depending on car/model you might have separate fans for the normal cabin air circulation and the AC cabin air circulations

Originally Posted by blitz_nomad

Thank you. A total noob here, what does checking battery capacity entail? Is there some metric that I can ask the service center to note - just to be sure that they'd indeed done it and to get a sense of my battery's capacity?

There are a lot of different capacity testers out there. The important thing is not just voltage. Although a low voltage (less than 11.5V) is always an indication of something wrong, it might not necessarily be the battery as such.

Battery tester should have at least two different tests:
1 Battery capacity: so it puts a heavy load on the battery and measures the amp, so it can calculate capacity in Ah.
2 (Cold) Continuous Cranking: It measure the Amps under simulated (cold) cranking.

Modern battery tester have a whole host of other clever function, including for instance telling you which cell is broken.

Very often the scale is not necessarily in units, but in terms as good/bad/sufficient etc.

Ask your mechanic how he test the battery, if he is only measuring voltage he probably doesn’t have a proper battery capacity measurement tool

Originally Posted by blitz_nomad

It's an automatic. Push-button start. Even though I was parked in the leftmost lane, I did seek help and had a few come up and help push the vehicle to a corner spot. I didn't try to start the vehicle when it was being pushed. Perhaps I should have tried that. Strangely no one suggested it either.

It is usually impossible to push start an automatic. Your owner manual will tell you what is allowed and what you should not do.

Originally Posted by blitz_nomad

It's a push button start. I left it where the music system works, but the engine isn't powered on. I did have the music system playing from time to time. Coming to think of it, I also had my dashcam plugged into the 12V socket. It's a Viofo T130. But it doesn't power up unless the engine is on. If it was up indeed, it should have been recording - I'll check to double confirm. Now I'm worried that the service center will blame it on the dashcam. No hard wiring, it's just setup to plug into the 12V socket.

With either the ignition on, or in the ACC position, the 12V is likely to be powered. But a dash cam will not drain your battery in a short period of time. Will run for many many many hours.

Originally Posted by som9729

1) Check battery charging and battery's practical capacity (I believe this is done by checking voltage, but I'm not an expert, so check other sources for this info)

No, the mechanic might tell you its the voltage, but a good voltage is no indication of the ability for a battery to hold its charge. Conversely, a low voltage is neither an indication of a bad battery. (Could be a problem with the alternator, the electrical circuit etc.)

Originally Posted by mayankk

I believe that modern cars will not be push started if there is zero charge in the battery. Something to do with alternators, which require at least a trickle of electricity.

Not so much the alternator as the ECU and other electronics. It needs a certain minimum voltage to work. Pushing a car with a dead battery won’t get you up to that threshold voltage.

It’s also the very same reason why cars with poor batteries can be cranked but won’t start. During the cranking, the battery voltage will drop. On a poor battery the voltage will drop below the ECU minimum voltage threshold, whilst still cranking over! Push start under these conditions might well work!

Jeroen

[d.w.w.]

Originally Posted by Jeroen

If your battery drains in a matter of hours on ACC the first thing to do is to have the capacity of your battery checked. (Note, not just a voltage check, that is not good enoug)

Many years back, my wife's cousin and his friend slept on a Scorpio with blower ON. The blower continued to work for many hours and it was only in the morning that they realized the battery was drained that too when they tried to start the engine.

If your battery drains in a matter of minutes, there is something wrong with the battery and this is likely to happen again.(like if you leave your fog lamps on while engine is off). You may try to replicate the issue again in a safe place and check.

[som9729]

Originally Posted by Jeroen

See below

Hi Jeroen,

Any insight into AMT pump draining the battery?

[Neversaygbye]

Originally Posted by blitz_nomad

Thanks for the tip on the cable. I've decided to get the same. Do these vary depending on the car battery?

Yes they do - usually the supported aH rating is mentioned. However, I have used the one I have (which is rated for 35aH) with my 55aH battery without any issues.

[blitz_nomad]

Planning to get some emergency/utility equipment:

1. The owners manual says battery capacity is 12V, 60Ah. What gauge/rating should a jump start cable be? Would this Amazon Basics cable do? (Seems to be rated for 35 Ah)
2. On the window hammer in the same product bundle - Do these actually work? Wondering because I recall seeing a video link posted here of some workshop trying to break open the glass for an owner that was locked out of his car. The window took several blows with a large hammer and still didn't budge. In the end, he used a large screw driver like a chisel and the hammer on it. (Tried to search for the video, but couldn't find it).
3. This multi-meter- I've never owned one. Would likely use it for household and the car. Any thoughts?

Manual says, when jump starting the car the booster battery needs to be of the same "capacity" and rating. If one is getting help in the highway, it might likely be another car of a different make. Just curious as to what happens if the batteries are not matched?

[Jeroen]

Originally Posted by som9729

Hi Jeroen,

Any insight into AMT pump draining the battery?

To be honest I don’t know. I would not even know if your car has an electrical driven AMT pump. There are quite a few different type of actuation mechanism out on the market for AMT.

But we can make a couple of assumptions. Car designers are unlikely to power any major electrical equipment in the ON position for obvious reason. So it either draws very little power or is powered upon the engine firing.

You could probably just listen for it, if you can’t hear a pump running with the key in the ON position, it’s either not powered or just pressurised the hydraulic circuit.

Jeroen

[audioholic]

Originally Posted by som9729

Hi Jeroen,

Any insight into AMT pump draining the battery?

Magnetti Marelli AMTs are designed to run as long as the ignition is ON or even if driver door is open to facilitate quick shifts upon starting the car or even when engine is off. This has an electrically driven hydraulic pump which builds up pressure in an accumulator. Once every few minutes, the pressure in the accumulator drops and the pump keeps topping it up. You can hear this whining noise as soon as you open the door while entering the car, or once every few minutes of operating the car.

Since this is a hydraulic pump, it is a significant consumer of electrical power and unfortunately, there is no check to prevent this from happening when battery voltage goes below a certain threshold. Rather this check might even have negative side effects that if you leave it in gear and turn off the car, a low battery can completely render the car in a non startable state since the car in gear cant be moved to neutral due to no hydraulic pressure and this would prevent engine start even if there was just the required charge to start it.

Ideally there must have been a way that the ignition and heavy consumers of electricity must be shut off after a certain period of non activity irrespective of the car being unlocked or in ignition mode. This would prevent such occurrences.

[Jeroen]

Originally Posted by audioholic

Magnetti Marelli AMTs are designed to run as long as the ignition is ON or even if driver door is open to facilitate quick shifts upon starting the car or even when engine is off. This has an electrically driven hydraulic pump which builds up pressure in an accumulator. Once every few minutes, the pressure in the accumulator drops and the pump keeps topping it up. You can hear this whining noise as soon as you open the door while entering the car, or once every few minutes of operating the car.

Since this is a hydraulic pump, it is a significant consumer of electrical power and unfortunately, there is no check to prevent this from happening when battery voltage goes below a certain threshold. Rather this check might even have negative side effects that if you leave it in gear and turn off the car, a low battery can completely render the car in a non startable state since the car in gear cant be moved to neutral due to no hydraulic pressure and this would prevent engine start even if there was just the required charge to start it.

Ideally there must have been a way that the ignition and heavy consumers of electricity must be shut off after a certain period of non activity irrespective of the car being unlocked or in ignition mode. This would prevent such occurrences.

Thanks, interesting. But I don’t think the hydraulic pump or rather it’s e motor is a significant electrical consumer. It’s only 30-40 bar pressure and with a low volume being displaced. More importantly it has an accumulator. So as soon as it reaches its set pressure it will switch off. With the ignition in the zo’n position there is power to the e motor, but it is not drawing any current, this being an hydraulic pressurised system it should not loose its pressure, until the system is put to use to change gears. So under those circumstances virtually no electrical draw.

Would be interested if somebody could check the fuse rating of this pump? I doubt it will be more than 15A, probably 10A. Say for argument sake it is fused at 15A. Obviously under normal circumstances it will not draw 15A. But even if it did on a 60Ah battery it would run for four hours!

Jeroen

[TheHelix0202]

Originally Posted by arijitkanrar

Many asked if a car battery can power the AC without engine running. I'm not sure of Tata Punch but our Ford Figo can and does run the AC with Ignition On without engine running.

Our Ecosport doesn't do this. Guess it depends on the car, even within the same company.

[Jeroen]

Originally Posted by TheHelix0202

Our Ecosport doesn't do this. Guess it depends on the car, even within the same company.

Google Ford Figo compressor. You will get a billion images and links to part shop. Each and every one showing an AC compressor with a pulley, so belt driven from the engine, not an e-motor.

As I mentioned before if you just switch off the engine and the AC had been on, the ACBlower will still circulate air across the evaporator which has a lot of residual cold. Once that has dissipated there is no more cooling. Other than the cooling you get from any normal ambient temperature air fan.

Again, let’s just do the math. It depends a bit on size of course, but a typical car AC will draw 3-4 horsepower. On the Figo you have a simple clutch on/off control mechanism as far as I know.Let’s say for argument sake the AC cycles 50% on 50% off.

3-4 HP on average is 2900W. With our 60Ah battery it will last 3600 minutes divided by half of the 2900. So your battery will last minutes!!

Jeroen

[audioholic]

Originally Posted by Jeroen

Thanks, interesting. But I don’t think the hydraulic pump or rather it’s e motor is a significant electrical consumer. It’s only 30-40 bar pressure and with a low volume being displaced. More importantly it has an accumulator.

The AMT hydraulic system operates at a max pressure of 60Bar and usually maintains accumulator pressure between 50-60bar and 40 being the absolute low below which it detects a fault(in case the pump hasnt kicked in by then and replenished the pressure)

There are minor losses in the system and what happens is when ignition is in ON state, the clutch is continuously held in open position. This requires pressure to be topped up and hence the pump runs once in a while to replenish the pressure.

Originally Posted by Jeroen

Would be interested if somebody could check the fuse rating of this pump? I doubt it will be more than 15A, probably 10A. Say for argument sake it is fused at 15A. Obviously under normal circumstances it will not draw 15A.

I am afraid thats not so. Pump alone has a fuse of 40A and is a significant consumer of power. Along with this the valve body has a fuse rated at 10A and then the control unit at 7.5A. Of course the valve body and controller would not draw so much power but the pump when running without engine on dims the interior lights in my Celerio.

And the battery on small petrol cars like my Celerio or even the Punch would be rated at 30-35A and definitely not above 40A. Hence, this along with the AC blower which also has a high current consumption, and the ABS also building pressure once a while, it is not a good idea to keep the vehicle in ON position for more than a couple of minutes at most.

[Jeroen]

Originally Posted by audioholic

I am afraid thats not so. Pump alone has a fuse of 40A and is a significant consumer of power. Along with this the valve body has a fuse rated at 10A and then the control unit at 7.5A. Of course the valve body and controller would not draw so much power but the pump when running without engine on dims the interior lights in my Celerio.

And the battery on small petrol cars like my Celerio or even the Punch would be rated at 30-35A and definitely not above 40A. Hence, this along with the AC blower which also has a high current consumption, and the ABS also building pressure once a while, it is not a good idea to keep the vehicle in ON position for more than a couple of minutes at most.

Thanks, that is very useful to know. Not quite sure why they insist on having all this lark powered without the engine running though?

As per your earlier post, it really ought to switch off.

Jeroen

[TheHelix0202]

Originally Posted by Jeroen

Google Ford Figo compressor. You will get a billion images and links to part shop. Each and every one showing an AC compressor with a pulley, so belt driven from the engine, not an e-motor.

As I mentioned before if you just switch off the engine and the AC had been on, the ACBlower will still circulate air across the evaporator which has a lot of residual cold. Once that has dissipated there is no more cooling. Other than the cooling you get from any normal ambient temperature air fan.

Again, let’s just do the math. It depends a bit on size of course, but a typical car AC will draw 3-4 horsepower. On the Figo you have a simple clutch on/off control mechanism as far as I know.Let’s say for argument sake the AC cycles 50% on 50% off.

3-4 HP on average is 2900W. With our 60Ah battery it will last 3600 minutes divided by half of the 2900. So your battery will last minutes!!

Jeroen

Yeah, I figured that was the case. I was confused as to why the dude would say his Figo’s AC ran even when the engine was shut off.