Can you swap a battery over while engine is running ?

 

dunno,yhink you might get a electric shock like.

let us know how it goes.

 

No the engine will cut out

 

well my dad had an old volvo he was scrapping, but kept the battery, so took it off while running and drove car to scrappy with no battery on..

 

No

 

dont think a petrol would as it needs a spark but a deisel doesnt so surely would keep running?!

 

how are you going to keep the electics running if you disconnect the battery?

 

? car only really uses battery for starting most of components run off alternator would not advise this due to power spikes blowing things up drive car to top of hill change battery bump start on way down job done

 

old diesel engine or some carb petrol engines yes
modern diesel or petrol not a chance mate

 

You need a good (heavy duty) set of jump leads and a battery.

Connect the jump leads to a spare battery and to the battery terminal leads (not the battery terminals themselves).

Disconnect the battery from the car leads and remove (making sure not to let the jump leads touch anything).

Fit replacement battery back into cradle and connect leads.

Remove jump leads and job done.

Not as easy as it sounds and you need 2 people.

 

Yes you can, the alternator output will keep the system live, but not a good idea.
This is why the cut out switches used on track cars have to be approved, this is because not only do they disconnect the battery live, they also cut the ecu power(supposed to cut coil but ecu does same job), they also have a small resistor going to earth from the live terminal that grounds when turned off, otherwise it would fry the alternator over time.
Some very new clever systems may cut the engine, when they sense the different resistance between battery and not, but certainly anything cossie age will run merrily with no battery, remember the alternator once rotating and having recieved a positive to get charging under way won't stop outputting till it stops rotating, it's of course connected to the positive terminal leads so that's why it keeps running.
tabetha

 

^^^ Aye .. Self sustaining once its exited ..

 

No they won't. Been there, tried that.

I have had a car with the engine running @ a show where someone decided to shut the door and the central locking "cycled". Only way to shut it down was to get the bonnet opened and disconnect the battery. The engine died IMMEDIATELY after the battery was disconnected.

If the engine stays running, you have something wrong.

 

true that, i was there pointing at stuff to look for with the screwdriver

just waiting for soemone to blow themselves up trying it

 

Total bollocks actualy.
You ever thought a immobiliser may have cut in ?
Will a(petrol) car run without power , think we're all agreed on no it won't, where does the power come from ?, the battery, where does the battery get it from ?, what condition does the engine need to be in in order to supply electricity, RUNNING, the system is kept live.
Ask any half brained track racer why the FIA ONLY approve battery cutouts that also cut the ecu feed, and the ignition feed.
Same way a motorbike without a battery, such as a serious dirt or trials bike stays running, ie it has something, usually a magneto producing electricity.
Simple fact of life once the BATTERY excited alternator starts charging, it doesn't stop charging so long as alternator is turning, this is why after switching off, by killing the power to the ecu/ignition it needs to be re excited through the 12v live delivered by the charge warning light for it to start charging again, the ecu ignition system lights etc, have no idea where the power comes from, it comes down the same wires, that the alternator is attached to, if you put on way too much electrical load on the alternator it would cut the engine, purely due to low voltage not being suffecient for spark.
The battery is mainly there for the starter motor, that is why really early cars with starter handles didn't always have batteries, but still ran perfectly, it also serves a function to help stabilise the voltage, and to supply current when the demand exceeds the supply(from the alternator).
tabetha

 

In theory you are correct, according to books. In reality, 99.8% of all cars on the road ATM draw too much to stay running. In addition, the battery "makes" the connection on most vehicles. Break the "connection" and the circuit drops and the power disappears.

Even my cabriolet which has no ECU, no injection, nothing other than a coil and ignition amplifier will not stay running. My 1953 Ford "Pop" might, but that has a starting handle.

So, all I have to say is to ask Dojj........., or video yourself taking the battery terminals off your Cosworth while the engine is running.

 

it was at ford fair
ian had the boot open
car was running
someone closed the drivers door
the central locking kicked in
he shut the boot
car was locked but running
ian panicked
he was about to break a window
i said "hang on, do this and that"
we got the bonnet open
undid the positive terminal
car died
i informed him of some jiggery pokery to get the central locking cycling in and out
someone opened the door when this happened
battery connected, the car started up

some parts of this post have been edited to prevent any srcotes using the information to open doors

 

im with tabetha on this one.
iv been their many times, most the time the stay running, on the odd accasion it mite stop tho.
i thaught every one new this!! especially ford people, and doubley especially cossie drivers.

 

Aye .. Depends on how the Alternator is wired in ..

Av seen this Happen on Electric drive Haulers .. Once the current starts to flow it will self excite and regulate enough stand alone ..

 

i agree, last time i took a car to the scrap yard it was a mondeo zetec r reg i think, started it took battery out n drove it there no bother, did die at the weigh bridge tho but jus rolled it down the hill lol, also kept my old 306 runnin when changing the battery so didnt loose key code in stereo!

 

I learned today my escort gti stays running i pulled the live off as i forgot to tighten it up lucky really i suppose or i wouldnt have known it was loose

 

Err has no one asked the question why the op wants to change a battery with the engine running?!

Just turn the engine off, stick a good battery on, and start up again, much less hassle and chance of getting a DC belt up your arm.

 

mate you could stick your tongue on the battery while changing it and still not get a shock only belt ive ever had off a car was a plug lead with the shroud rubbed through lol and ive been working on them every day for well over a decade!

i presume he wants to change it while running to avoid losing radio code, problem is on most modern cars remove the battery break the circuit so knackered anyway

 

I've still got a scar on my wrist from a car, was fucking about changing the intercooler on my old Pulsar, and the ally pipes run really close to the battery terminals, somehow managed to short my metal wrist watch and intercooler pipe against the positive battery terminal, and the current must've heated my watch up to a few hundred degrees as it actually melted a bit of the steel strap and burnt itself into my wrist

So I'm always a bit weary round batteries and stuff these days!

 

thats a bit different tho mate because you made yourself a circuit lol! bet it fucking hurt tho heard horror stories about spanners being dropped across terminals and batterys exploding so it can happen but so long as you are careful and dont earth the live terminal you will never get a big belt off one

 

did a similar thing was tightening a loose connection and shorted the spanner onto my watch which was toughing the body, got a scar from that too. lol il never do that again!

 

Aye arc'ing out is nasty ... Try it with 24v ... Hell on earth for a few seconds ..

 

So how do cars manage to go on long journeys? Because based on that rationalle they'd run out of electricity surely if the demand was greater than supply?

Some cars will run with no battery, as several posters has testified, but some cars won't - I'm no auto electrician but I'd wager it was a connection issue and not a sufficient supply issue.

 

You should NEVER run a car without a battery !!!
(especially if you intend to keep the car )

Yes an alternator will supply more than enough energy to run the car without a battery, thats its job !

However, a battery is a load that is needed for proper voltage generation and regulation even if it is fully charged.

Remove the battery,and the alternator will work harder trying to staibilse its output causing it to heat up and
in some situations the open circuit voltage may rise alot higher that the 12 to 14 volts !

Also, it is a very good suppressor in that the battery absorbs voltage transients generated from all the inductive devices on the car such as injectors, coils, and the alternator itself.

If you remove the battery, you remove this absorbing safe net and this will degrade and reduce the life of all semiconductor components that are in the car such and ecu's, stereos etc...

It is possible to cummulatively damage electronics without noticing any ill effect.