Check your battery terminals

Post by **Peter.N.** » 26 Apr 2005, 05:00

Yes, you probably could, but you would have to get it going fast enough for the alternator to cut in, so as to power the fuel solonoid (diesel) or ingition system. Also as there would be no battery back up, if the power demand exceeded the output of the alternator there would be no reservoir to keep the voltage up and therefore the current down, so you could burn the alternator out.

AndersDK · Post by **AndersDK** » 26 Apr 2005, 05:09

Sorry Peter -
Forgot to mention I meant on petrol cars. But should be possible on diesels as well.
Yes it can be done Peter - without no problems at all - i.e. flicking headlights, heaters, blowers on/off while engine (and alternator) is running.
I did it with my old CX when I had to move it out of the way. But of course : too light a foot on the acc on load - and it is dead immediately.
I thought it should work like how you start up a power station - and of course it does.
Modern power stations are purely self contained and regulated. In case of power down they either need a battery back up - or to pull energy from the net - to get "on the net" again. Because they need excitation energy for their alternators.
Fastandfurryous :
I believe Peter was referring to the events where you can see the charge lamp coming on - with the engine near stall.

Post by **Peter.N.** » 26 Apr 2005, 05:20

If you watch your interior lamp as you increase the engine speed, you can see the point at which the alternator starts to put out serious current. In the days of dynamo's (if you are as old as me) the battery did most of the work on heavy load because the output even when they had regulators was a maximum of 19 amps, before that time even less, hence the need for a much heavier battery than of now. Dont know to much about petrol cars, have run diesels for years, used to convert them before you could buy decent ones.

AndersDK · Post by **AndersDK** » 26 Apr 2005, 05:32

The charge lamp always tells you Peter.
The reason why any dynamo or alternator makes the light brighter at increased revs, is of course because the voltage is increasing to reach the regulated point.
If the output is not sufficient - then the remaining energy must be borrowed from the battery - and then the charge lamp immediately tells you.
It was somewhat "lumpy" with the dynamo setup - as you had a current relay switching in/out to regulate.
Yes - I have silver hair [:I]

Post by **Peter.N.** » 26 Apr 2005, 05:43

I wasn't refering to the charge lamp, I meant the interior illumination lamp. The charge lamp only tells you that the charge lamp has gone out, the interior lamp, or any others you can see, actually shows you that it is charging. Yes, I remember the dynamo regulators, they should be set to 16.1v but people used to screw them up and burn the dynamo out. Did you ever have a car with 6 volt electrics? I had a pre war Ford prefect,the lights were dreadful, a friend of mine who made manufactured batteries made me an 8 volt one, tremendous improvement. The dynamo output was ajusted by a movable third brush, I had to take it out and connect the field directly to the output to get enough charge.

AndersDK · Post by **AndersDK** » 26 Apr 2005, 05:52

I'm only 52 Peter [:D][:D]
But my first car COULD have been a 6Volt - a VW type 1. Still loads of them on the roads when I was young. Instead it was a '64 Morris Mini 850.

Post by **Peter.N.** » 26 Apr 2005, 05:57

Just coming up 66, it was in 1956 I had my 6 volt Ford. There were a lot of VWs about, still are quite a few but I think they are 12v now. Going to bed now, nice talking to you.
Goodnight.

Post by **Peter.N.** » 26 Apr 2005, 06:01

I'm coming up 66, I didn't have the car pre war! had it in '56. There are still quite a few VW Beetles over here but I think they are mostly 12 volt now. Going to bed now. Nice talking to you.
Goodnight.

jeremy · Post by **jeremy** » 26 Apr 2005, 13:44

Well Anders I'm your age but my first car was 6 volt - a 1946 Austin 8. This was fitted with an ammeter and the battery was quite large with a moderate capacity and I had no problems with it even with what must have been uprated twin filament headlights - the original system provided an dip by turning off the off side headlight and deflecting the near side one with an electromagnet!
There were a number of reasons for the change over o alternators, one of the reasons being engine spped. Apparently the armature of dynamo's as then constructed were considered safe for about 6000 rpm, and an alternator which is of course much simpler and has claw shaped poled folded over the rotating bit is sfe for 12,000 rpm. No problem with diesels and most 50's cars - run at a bit over engine speed - dynamo gets to useful revs at relatively low engine revs and copes. Along comes daimler V8 and lotus engines - 6000 rpm no problem - so now you can't evevn run the dynamo at engine revs - and so with increasing traffic queues, bigger headlights, heated rear screens and so on you could run the things flat quite easily.
In fact both dynamo and alternator start to provide useful output at about the same machine revs (this is against a well charged battery) but the alternator provided some relief as it could be run faster - about twice as fast - so its output at low engine revs is much better - but I nearly ran an XJ6 flat in snow (20 MPH in drive on an auto) and was lucky to notice the voltmeter in time.
As a matter of interest I was investigating a Range Rover 4.2 yesterday that has suffered from mysterious battery discharge. the starting (no load) battery voltage was 12.6 which suggests that this was properly charged and sound. No load voltage rose to 14.09, and under load it was running at 13.63 at 3000 rpm. (actually reached this figure below but for test purposes I was only interested in 3000 rpm.)
With a dynamo it was perfectly possible to remove a battery with the engine running providing the revs were kept above idle. I've never tried it on an alternator system which always used to regard as a fault waiting to happen (am I wrong now?)
Of course the greater the alternator output voltage the greater the effective voltage of the car and the better the lights will seem to work. The problems are damage form the incerased voltage and the battery boiling that will take place if its charged at excessive voltage.
Jeremy

ItDontGo · Post by **ItDontGo** » 26 Apr 2005, 14:35

If the wire comes off the battery then the torque the alternator requires to turn it will instantaneously diminish. Therefore the alternator wont suddenly have to do something with all that power because all that power wont be being generated.
The voltage induced in the coils will not increase very much either when the battery is disconnected as they will have a very low resisitance and hence the loaded and unloaded voltages will be close.
I cant see why it would necessarily damage the alternator to be honest. What will happen is that the electrical system will be unsmooth which means the electronics may suffer and as they have to last years there is usually no electrolytic capacitors in cars which would dry out.
By unsmooth I mean the output may go from 0 to 14v every hundreth of a sec etc... whereas with the battery it would make this a constant 12 or 13...

davek-uk · Post by **davek-uk** » 26 Apr 2005, 14:46

DOH! Don't tell me all this! Please leave me - on the odd occasion like this - in ignorance...
Due to the AX being surplus to requirements, SORN and without MoT (poor thing), I usually leave it some weeks between starting it. The battery is very old (and duff) and although I disconnect it between starts it always needs a jump start. I have often run it without the battery connected, taking the positive lead off after it has started. So far I haven't noticed the alternator packing up but now I'll have to check it. Oh no...

Post by **Peter.N.** » 26 Apr 2005, 15:59

Re Fastanfurious's point concerning alternator output at low speed, just watch the illumination intensity of your overhead light when the battery is in a low state of charge i.e when you have just started the engine, increase engine speed slowly and you will see the brightness increase. To Anders, I did send you another reply last night but for some reason it didn't appear.So I gave up and went to bed
Peter.

madasafish · Post by **madasafish** » 26 Apr 2005, 16:10

My first car (a student) was a 1929 Riley 9 (I'm 57:-). The dynamo was mounted directly on the end of the crankshaft. There was a switch to stop it charging over about 35mph as there was no current control and it fried the battery/and wiring if you did not switch it off.
I refer of course to a manually operated bakelite switch mounted on the dashboard.
Magneto ignition as well...
Oh how cars have changed.. Mind you it had a fabric body, front facing doors, thermosyphon cooling and a nickel plated radiator.
Those were the days..not. Great fun to drive then. On today's roads, definitely not.
Sorry for being off topic...

Post by **Peter.N.** » 26 Apr 2005, 16:22

I didn't know we had so many wrinkles reading this. Please excuse my duplication of posts, I thought they were not being posted, but of course they were on the next page! I blame the age! My first diesel had a dynamo, it was a 1956 Vauxhall Cresta which I had fitted with a Perkins 4/99 engine, needed a huge battery on that to stand any chance of starting it on a cold morning, I think it was about 100ah.
The advent of the alternator has permitted the use of batteries with so many thin plates that they will still start the engine with about 90% of the active material lost, but go flat if you leave your lights on!

fastandfurryous · Post by **fastandfurryous** » 26 Apr 2005, 18:37

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Peter.N.</i>

Re Fastanfurious's point concerning alternator output at low speed, just watch the illumination intensity of your overhead light when the battery is in a low state of charge i.e when you have just started the engine, increase engine speed slowly and you will see the brightness increase.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
On some cars, yes, I've experienced the "headlamps get dimmer at idle" but on others, and indeed my current one, no.
After starting, even with a battery in a lowish state of charge, the voltage is instantly at 14.4 volts. Even at a very slow idle (700rpm or so) with as much electrical load as I can put on it, it point-blank refuses to drop below 14.4 volts. With no-load, and a good battery, some time after starting the engine, and at 3000rpm, the voltage is still 14.4 volts. I'm guessing this is just a damn good alternator!
David.