View Full Version : question - can a car be started without a battery
DaveMark
13-06-2003, 13:40
me and my m8 were arguing can a car be started without a battery and if so how, we are talking a semi modern car here
dave
slartiBardfarst
13-06-2003, 16:30
i don't think so. you can get it going if the battery is too flat to run the starter motor by pushing it up speed and dropping the clutch, however the battery is still needed to produce the spark and burn the fuel mixture.
i'm pretty sure that the engine doesn't generate enough energy to produce a spark from just a push start with no battery.
once the engine is running the electronics are powered from the engine so you would only need a battery to start it, not to run the car.
DaveMark
13-06-2003, 16:32
so it all comes down to if the car would produce enough to make a spark
dave
slartiBardfarst
13-06-2003, 16:48
well on all cars you have what's called an alternator. this is just like a big motor running in reverse from the engine rotations, so it produces electricity. it will only make electricity if the engine is running at speed.
i'm sure you can imagine that just pushing a car along at 5mph does practically nothing but move the engine round so no electricity will be made. hence you need some form of battery to make a spark.
i suppose in theory, if you pushed the car quick enough or pushed it down a hill then you could get it going quick enough to produce enough electricity to make the spark and start the engine.
DaveMark
13-06-2003, 16:50
will have to try it and find out ;)
Big Adam
13-06-2003, 17:01
Er, aren't you guys just describing a jump start?
BA
DaveMark
13-06-2003, 17:02
a jump start uses a little bit of power from what ever is left in the battery ... we are talking about starting a car with out a battery ..
the descution with my m8 was if a emp hit would cars still be able to run
dave
no, it wouldn't start. if spark ignition you need 12v to run, if compression ignition (diesel to you) you need 12v to open the rack shut off valve.
you can push it down the steepest hill you can find and the alternator will not start charging because it needs a 12v feed to actually start producing electricity :)
K Hussain
14-06-2003, 03:41
It’s not possible.
Most modern cars (95 onwards I think) are computer controlled by an ECU (black box technology), so a battery is required.
Blue Raptor
19-06-2003, 23:35
they all have engine management so that has to clear before the engine starts
K Hussain
20-06-2003, 00:50
Originally posted by Blue Raptor
they all have engine management
from when?
Blue Raptor
20-06-2003, 08:47
most newer carss have it in some form
master baits
20-06-2003, 15:35
The most accurate part in here is that most modern cars wont or shouldnt be jumped started , 1 because of its injection sytems or 2 because of crd cant or wont open the deisel valves.
Older cars however can and will be jumped started without a battery injcluding deisels by jump starting , why do you think there was crank starts on cars as recent as the almost laughable simca - to mid eighties.
I have started engines both deisel and petrol without batteries on test beds (college back in the halcyon days) so therefore cars prior to ecu and injection WILL and can be started without batteries and run .so long as they still have a soloniod , alternator and starter much akin to a propplane engine (not including the ballastic start ones of ww2.
Hell just watch scrapyard and it will be confirmed most weeks.Simply think of a petrol lawnmower , it has no battery (unless your very posh and can sit on yours) and it is rolled on with a cable to the armatuer creating a spark for the first ignition then it runs off the self generated electricity to the plug.
yes you can start a lawnmower without a battery but only if it has a magneto, ie an ignition coil energised by a rotating magnet, this applies to most domestic machines, but commercial machines ie anything above about 5k in price do not have magnetos and are similar to cars. you cannot start a modern diesel engine without a battery, you need 12v electric to pull off the etr solenoid, as I said in earlier post spark ignition engines need 12v to produce the spark, so will not start without a battery.:)
master baits
20-06-2003, 21:18
the energy for the initial spark is generated exaclty how you mention , the question was can a modern car be started without a battery. and as you and i have pointed out the answer is yes.....
As long as the electric is generated for the initial hump ,be it starter handle a pull coil or a bump start a car or more precisely an engine can BE started without a battery be it deisl or petrol lawnwmower or tractor.
no modern spark ignition car can be started without a battery, no matter how fast you push it, the alternator WILL not produce power without the input of 12v to excite it, nothing comeing out of alternator + no batterry = no spark, no spark= engine not starting. really old cars used dynamos, if you got car going fast enough it would produce voltage and would start. diesels will start without a batterry provided they do not have an energise to run (etr) solenoid fitted, this needs voltage to pull the engine stop off, if this is not pulled off, no fuel flows to injectors. the question was would a car start without a battery, i think they were talking about a modern car, so the answer has to be no.
master baits
21-06-2003, 00:52
As i have said i have started engines and therefore cars without batteries , they have run without batteries , the engines were on test beds and manually turned over WITHOUT batteries.LAst one being a 16v zetec in winter , and your not meant to with injection systems eh.
But if you want to say it isnt so then thats your opinion , this is I can assure you is wrong and is blatently obvious to the educated reader.
Previousl I mention the mower engine , and prop plane now Motor scooters , ie piaggio vespa until recently did run without batteries and are kick started before they went electric start , rally cars and f1 cars also using pnumatic starters that turn over the engine.
By the guys defination of modern car and without a battery he could mean a prior to zetec fiesta(or to any injection based one) using the 50 yr old based ohc engine which can be turned over therefore started without a battery by bumping the engine in gear or pnuematic turnover of the starter.
I just love those that say can't or wont rather than "how can I" , I know some folk like this that havent a clue and think they do worse still they end up being your boss cos they are yes men.
DaveMark
21-06-2003, 02:31
wow this thred has lots of diffrent views thanks every one its just made me want to rey to take my battery out and start her up lol
dave
if you read the initial post it says car not test bed. how did you power the ignition system on the test bed, because you must have got power from somewhere, NO three phase alternator is going to produce voltage without being 'excited' and I repeat you MUST have voltage to produce a spark at the sparkplug, no spark no engine running as in ' in,squeeze, BANG, out'
and as for comments at the end which made it seem as if I don't know what i'm talking about, well thats me k*****ed, I might as well hang up my spanners after 30 years as mechanic LOL
:mad:
wizbongre
30-06-2003, 22:58
This thread has got me interested...
Firstly, I'm not sure what you mean by the alternator needing the 12v battery to excite it? Why does an alternator need an electric input to produce an electric output? Doesn't that kind if defeat its purpose? An alternator is just a fancy coil that produces an electric current due to everyday laws of physics - it takes a mechanical motion and turns it into an electrical current...
Also, an average alternator puts out a regulated 13-16V (usually about 14.5v) whilst being turned at anything above about 1000rpm give or take... When a car has a totally dead battery (as in a defective one) the car will ususally run for a decent time purely on the output of the alternator - the engine itself should run sufficiently as the alternator should produce enough power to fire the plugs and keep the engine electrics funtioning... Just don't put on the lights or interior fan!! The battery is mainly there to store power to enable the initial start of the car - which for the sake of this argument could be taken away and replaced with a mechanical mechanism, such as bump starting or using a crank handle.
I'm also not sure what relevance the ECU has - its only a smallish computer accepting inputs from sensors and producing outputs to components of the engine - as long as it has a sufficient enough power feed it should be fine...
All of this is just my understanding and probably a load of sh1te!! I honestly can't see any reason (for petrol engines anyway) why the engine wouldn't start without the battery. I'd be interested to see this proven one way or another...
DaveMark
30-06-2003, 23:07
lol wow this thred i have started has turned out well
dave
a car uses a three phase alternator which does not have any magnets in it, if you remember school and producing electric with a coil of wire and a magnet, you will realise you need magnetism to produce voltage. dynamos produce low power dc and three phase alternators produce high power ac voltage but need the magnetism to produce this. a coil in the alternator is fed with dc voltage (this is called exciting) now when turned it will produce voltage (approx 35v ac), this is fed to rectifier-regulator, which produces between 13.8 - 14.4 volts. Right thats how a car alternator works, so if it does not have a battery, how the h*ll does it excite the alternator and start it charging.
so, no battery, no charge from alternator, where does the spark come from:confused:
DaveMark
01-07-2003, 01:12
Originally posted by rowland
a car uses a three phase alternator which does not have any magnets in it, if you remember school and producing electric with a coil of wire and a magnet, you will realise you need magnetism to produce voltage. dynamos produce low power dc and three phase alternators produce high power ac voltage but need the magnetism to produce this. a coil in the alternator is fed with dc voltage (this is called exciting) now when turned it will produce voltage (approx 35v ac), this is fed to rectifier-regulator, which produces between 13.8 - 14.4 volts. Right thats how a car alternator works, so if it does not have a battery, how the h*ll does it excite the alternator and start it charging.
so, no battery, no charge from alternator, where does the spark come from:confused:
my little helper who i keep under the bonet with a match :p
dave
Jamez_Warner
14-03-2005, 12:32
if an EMP hit cars would certainly NOT work, the ECU would be fried
James
Firstly, I'm not sure what you mean by the alternator needing the 12v battery to excite it? Why does an alternator need an electric input to produce an electric output? Doesn't that kind if defeat its purpose? An alternator is just a fancy coil that produces an electric current due to everyday laws of physics - it takes a mechanical motion and turns it into an electrical current...
Yep - as has already been stated, this works due to a conducting wire being passed through lines of magnetic flux. Alternators produce this flux by means of an electromagnet, which requires power. Use permenent magnets instead and it should work.
it's easier to just fit a dynamo.....
as long as you can crank it fast enough then it will start.
Daleaholic
15-03-2005, 19:43
what about if you have an in car computer which runs on batteries? could you start up a car with these? :confused: Sorry it just came to my head and posted.
davee10000
25-03-2005, 15:30
Hi All.....
I can see there are a few people here who may be able to help me!
I've a boat fitted with a 1300 ford engine.
When i connected the battery, the alternator started to smoke!
Can I bypass the alternator to start it and how?
Obviously I'd need to charge the battery myself, but this isn't a problem I just want to get the thing running!
Cheers,
Dave
if it is a ford 1300 crossflow engine then yes, just unplug the alternator. it means though that when the battery dies you will be dead in the water as there is nothing to generate the sparks.
i would just replace the alternator and then your only limit is your fuel supply.
i would just replace the alternator and then your only limit is your fuel supply.
And dont forget the other limit - where the water stops and land starts :P
davee10000
26-03-2005, 01:28
Cheers guys for the replies... will let you know...
its ford 1300 kent thats been marinised...thats all i know at the mo' I bought it a week ago Its been stoon for a year but engine turns a bit until you feel the compression... There was no battery but was told it should go....! When I hooked up a battery the alternator started smoking. I unhooked battery.
Will try again. Cheers
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