battery disconnected! Dont they require a small amount of input current to magnetize the rotor!
tmenz,
May 24, 12:22pm
There'll be a small amount of permanent magnetism in the rotor - enough to start it generating some voltage - once going, it builds up and is self perpetuating.
ginga4lyfe,
May 24, 12:51pm
to start the car you need the battery, its the battery that excites the windings int eh first place, once the coils are excited, so long as they dont stop moving ( or go below a certain RPM) they will continually create energy regaurdless of the battery being there as it will continually keep itself excited
sgrants,
May 24, 2:34pm
. . . and more than likley burn out your alternator as it has no battery for the voltage reference point so the alternator will try to compensate at it's maximun out put !
ginga4lyfe,
May 24, 3:21pm
nope, it wont, but the car will not be able to compensate for various unstable loads, like stereos, sometimes also if you have the lights on and put the indicators on that can cause the output to flactuate,( causing slight rough running or cutting out ) but it wont burn it out, all the battery does is allows the alternators output to be further stabilized and provide for further outputs that the alternator may not be able to withstand at times
bigfatmat1,
May 24, 4:43pm
alternators in an open circuit is a bad idea as the voltage will increase untill alternator self destructs. A lot of alternators only need voltage to get them going.
high resistance in batt supplies is a common cause of rectifier failure
mrfxit,
May 24, 6:52pm
LMFAO. . . blah blah blah . whatever . ;-)
Lets just agree that for whatever reason, it's a REALLYbad idea to run an alternator without a battery connected. Basicly it's ASKING for trouble & it's mostly a matter of luck if it buggers up or not. Same for using an arc welder with the battery connected.
ginga4lyfe,
May 25, 5:50pm
and here i thought the Regulator regulates the voltage.
bigfatmat1,
May 25, 5:54pm
it does.- .When its in a circuit. no ground no power no regulate
ginga4lyfe,
May 25, 6:03pm
hmm, you may be right, but it is a complete circuit otherwise it would not be a self sustainable output like it is even with out the battery, the ground is the the body of the alternator, and the back end of the rectifier pack and regulator isnt it!, Meh Ill leave it to you the fully qualified one to varify whats right or wrong
bigfatmat1,
May 25, 6:34pm
lol you are confusing ya self.
ginga4lyfe,
May 25, 6:35pm
Most likley, I have forgotten alot from not doing it
skin1235,
May 25, 6:40pm
the battery actually supplies a resistance and it is that resistance that the regulator uses to "balance' the supply - without it the regulator will either not supply sufficient excitement to the fields or be completely uncontrolled , and the little 12v alt in your car will (for a time) pump out up to 80v, sometimes higher ( and definitely of a detriment to the rest of your 12v system) check this yourself, spin up an alt by another means, bridge between the bat and F terminals and check the voltage supplied ( keep your fingers out of the circuit - it bites - and when the rectifiers quits it bites twice as quick and twice as hard, then throw the alt away cos the diodes will be stuffed the field windings will be cooked and the brushes will be half melted) How do I know this - ask my now 40 yr old son about his experiments when he was a mere 14 yr old
ginga4lyfe,
May 25, 6:46pm
hmm , that was something that i never learnt i think then, and ill take ur word for it too, I dont have any spares laying around nor do i have access to a test bench anymore, well I guess you learn something new everyday, and I will now not be doing what i used to do. if a car wouldnt jump start
skin1235,
May 25, 7:08pm
the diff between generators and alternators are not that great, but they do have differences, a gen uses ferrous cored electromagnets to create the field force ( that the windings have to 'cut' to produce usable voltage/amperage) vary that field strength and the voltage/amperage varies too) even when the field current is stopped those ferrous cores retain some magnetism - suffice to create a field force without any input from the regulator, and tow starting due to a flat battery will always result in that self excitement causing the gen to supply useful voltage to the battery. tow start a gen equipped car with no battery and it will still fire up and be able to be driven - as long as you keep some revs on A gen creates DC current - its regulator controls both voltage control and amp control to balance battery conditions and or systems loadwhereas an alternator uses non ferrous cores in its electromagnets, no residual magnetism remains once the fields are turned off, therefore it cannot self excite ( tow starting a car with a very flat battery and an alternator can result in no excitement thus no charge being produced by the alternator thus the battery remains flat ( ALL field strength is controlled by the regulator - no residual) and the engine will not run for long - ( only as long as there is sufficient current to fire the ignition coil)( alternators produce alternating current which then has to be converted to DC current - diodes and some clever thinking makes it easy -) I've never tried to tow start an alt equipped car with no battery, perhaps it would work but I would seriously expect there to be some damage, big damage, to the systems if it could be done now of course many will come on and tell us how they run alt vehicles without batteries all the time
mrfxit,
May 25, 7:17pm
Agreed. That would go a long way to explaining the output possible with the "alternator welder" converter plans. You can apparently get a short cycle arc welder by combining 2 or more alternators in series. ! . yes !
skin1235,
May 25, 7:46pm
I do know that when you roll the hilux down a gully, and the battery destructs against the engine, radiator, inner guard, engine, radiator, etc until it breaks completely in half, and the engine is still going, the loom tends to get very hot, the voltage gauge goes completely off the top of the 20v scale, the alt will eventually stall the engine if the belt is tight enough, or as in my case slip the belt on the stalled alt - that when the fuel shuttoff shut it down, that alt is still in there and still working - course the door doesn't shut as well as it used to and theres a bit of a problem with the lights and wipers etc - anyone got a spare LN65 for parts lol
a18a,
May 25, 9:33pm
on the subject of alternators. i had a early 90s honda prelude, the alternator failed in some way that the charge light came on & when i revved the car, the sunroof opened half way, windows wound down half way, wipers wiped the windscreen & blew all the electrics inside the car, which then died. was pretty funny lol, but what would have caused that!
skin1235,
May 26, 3:05am
regulator lost the battery while running, then thought the battery was flat so increased the field load - and kept increasing that because it couldn't sense the battery voltage yet - couldn't find the battery so feed all it could into what it could find ( the earth system) result = -24v plus in your +12v system and climbing ergo haywire response from all electrical components. meltdowns galore
jason18,
May 26, 3:29pm
I have an alternator in my car.
bigfatmat1,
May 26, 3:53pm
mynes bigger
taipan4,
Apr 4, 3:03am
Some of the old english motor bikes had 6 volt systems, and o ne night I came out of polytech and the batteryhad been stolen from my 1961 triumph t,bird. Proceeds to push bike home & gets picked up by a guy with "apehangers" on his bike, takes me around to his placefinds a battery in the shed takes me back to my deadbike fitted the battery up somehow, lights were pretty dim, cop car stopped me, explaINED MY PLIGHT, "YOU GET STRAIGHT HOME SON" NO WONDER THE CALL jOSEPH lUCAS "THE PRINCE OF DARKNESS" lol19691st year apprentice, chch polytech
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