How far would a car run on the battery ?

No idea but, in mathematical terms it'll be: Petrol < common rail Diesel < mechanical injection Diesel - each requires less battery power to run the engine than the previous.

(And that only holds at this time of year. In cold weather some common rail Diesels use their glowplugs whilst running to keep cylinder temps up.)

Id guess if no lights, no aircon or fans, and no waiting in traffic, you might get away with a couple of amps, and you can get about 20 starts out of a battery, so up to 20 starts or 30 hours of driving, or whatever combination of the two..

Hmmm, you said: "each requires *less* battery power to run the engine than the previous" in which case it should be:

petrol > common rail D > mechanical injection D

and not:

petrol < common rail D < mechanical injection D

Which way round do you mean it to be?

Depends on so many things. Type of engine, so how much current the engine takes. For example, some older diesels don't need electricity at all to run. An older petrol car perhaps only the ignition. More modern cars, power needed for injection and ignition.

BTW, a 'low battery' light doesn't necessarily mean the battery isn't being charged.

mostly a warning light means just that. Not being charged. I have never come across a 'low battery'' light, just a 'charge not happening' light.

o lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded wit h goods and services paid for by the confiscated wealth of a diminishing nu mber of producers.

Thoigh I was driving it wasn't my car so interpretation of dash symbol may have been incorrect.

Sorry should have said it was a petrol engine.Honda Accord.

I thought he was answering in terms of the time it would last, in which case he was right the way he put it.

Some later cars with LCD displays have a low battery warning, I guess if you have electric power steering and such that you may want to know if the battery is lower than it should be...

Yes, my bad. Should have been ">". Having written much software in my life I am very familiar with comparison operators and the associated logic and don't get them wrong. But when it comes to this sort of written usage (and reading it) I get it totally ar$e about face in my head. It's a form of what I believe is referred to as TIS (Total Incompetent Stupidity.)

Scott

I dunno what is on every car, but the more common ignition warning light which goes out when the engine starts, doesn't always tell if the alternator is charging or not. Ie, the warning light circuit may be faulty.

I'm not saying it is in this case - but it would explain why the car appears to run for a long time with no charge, and the differing diagnostics from the two 'experts'.

For fred - it is pretty easy to check whether an alternator is dead or not. Simply connect a DVM across the battery. The voltage reading should be something like 14v if it is charging. Ie, about 1.5v more than the reading with the engine stopped.

Oh, I thought this would be an interesting discussion on how far you could drive a car using the starter motor. ;) I seem to remember seeing a video of somebody driving out of a river that way.

JGH

Me too. It's a long time since I had to do it, to get safely to the left of the road. I think the trick was to select top gear.

That'll get you the maximum distance per turn of the starter motor, but will have the slight disadvantage that the starter motor could well burn out :-)

Moral being don't get stuck in a river with an auto.

I haver certainly done a few tens of meters.

In fact its the only way to start a car with no clutch fluid....

yup. we built a go kart powered by two truck batteries and a starter motor., Good for a few laps anyway.

And maybe the steering.

I could do 20 miles between Doncaster and Barnsley when my alternator failed (no lights, no fan) and just have enough power to restart the engine at the end of the journey. I have no idea how much further I could have gone before the steering etc failed.

I managed that week by charging the battery all day whilst at work and then overnight when I got in from work.

Anyone know what happens now with start/stop buttons, you generally need your foot on the clutch before the starter will work. Can you mechanically crank the car in an emergency?

TW.

In article , Graham. scribeth thus

It is recommended for getting a car off a railway level crossing..

Mind you not a lot of use if the battery's shagged in the first place!...