electrical load on a generator

I know that an alternator can be sent up in smoke if it's run without a battery load connected.

Will a generator and/or its voltage regulator be damaged if they are run without a battery load connected? My logic says they will be damaged, but I want to get a firm answer from experts. (Just so you know, my knowledge comes from electronics and radio frequency stuff. What I've done with, and learned about, alternators and generators in cars, trucks, and tractors has been gained in large part by reading here what all you 6, 12, and 24 volt DC guys have graciously shared. Thank you)

(quoted from post at 23:53:33 05/06/21) I know that an alternator can be sent up in smoke if it's run without a battery load connected.

Will a generator and/or its voltage regulator be damaged if they are run without a battery load connected? My logic says they will be damaged, but I want to get a firm answer from experts. (Just so you know, my knowledge comes from electronics and radio frequency stuff. What I've done with, and learned about, alternators and generators in cars, trucks, and tractors has been gained in large part by reading here what all you 6, 12, and 24 volt DC guys have graciously shared. Thank you)

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e careful, as you will mostly get opinions, not facts. But a better question is, why ask about something that no one should do? Just to generate crap?

Why would anyone with a lick of sense try
To operate a machine with electronics without a battery ?

Back in the generator days, it was fairly common to disconnect a battery from a running vehicle. I don't recall any time this caused a problem. The nature of an alternator will produce high-voltage spikes when there's no load on it, but the residual magnetism in a generator will keep it charging slightly when there's no load. As long as there are no voltage-sensitive devices in the vehicle I can't imagine how it would cause a problem to run it without a battery. One thing you can do is to turn on the headlights, that will give a sufficient load to keep the voltage at a regulated level.

I'm guessing he's not the one trying to generate crap....

In despite of the one comment of turnning on the headlights then disconnect the battery. Don't do that. You will blow all the lights. BTDT when I was a teenager with a generator on a Farmall A.

Of course you shouldn't do it but it won't be the end of the world if you do. If the engine is running and there isn't a magneto you have a load.

This is something people get a little carried away with. It's a matter of time and connection. You can momentarily run a generator or alternator without hurting either one. The problem comes in if you make or break the connection with the switch on. That's where the spike comes in. Modern regulators can't stand the heat from full output of the high amp alternators for long at all.

Ron, as a past used tractor dealer and farmer who had to repair a ton of old tractor generator charging systems, I NEVER had or experienced a generator problem when I ran without a battery HOWEVER FOR THE RECORD AS AN ENGINNER I advise it not be done just to be on the safe side........

John T

Obvious you missed my point. Sorry.

Obvious you missed my point. Sorry

Thanks Pete.

I was referring to taking the wire off the BAT terminal on the regulator thereby taking away all the loads. (It's sometimes hard to express thoughts in writing)

There is no load when the wire is removed from the BAT terminal of the voltage regulator.

I see I somewhat opened a can of worms unintentionally by not explaining very well what I wanted to find out. Sorry for upsetting some of you posters.

With a red face and being embarrassed, I'm not going to try to explain what prompted my inquiry in the first place !!

Hey Ron, I see no problems here in asking a legitimate question. You did nothing wrong in my opinion and I gave a polite response. If there are any trolls or nit pickers or those who just love to fight or argue or must always be right others always wrong (you know the my way or the highway types) just ignore them is my advice.....

No reason to be embarrassed or red faced in my opinion

God Bless all here and best wishes to everyone

John T

I see 100s of engines ran with an alt and no battery connected. The only power is to the ECM from a remote source.

Hi Ron,
This thread is a perfect illustration of conversations you and I have had about this site. Lots of good info, but sometimes you have to sort through a boatload of crap to get to it!
Special thanks to John T. for his true knowledge and for his willingness to share it with the rest of us!
God Bless!

Thanks for the kind words, now if only the first wife thought as well about me lol lol

John T

(quoted from post at 10:16:54 05/07/21) I see I somewhat opened a can of worms unintentionally by not explaining very well what I wanted to find out. Sorry for upsetting some of you posters.

With a red face and being embarrassed, I'm not going to try to explain what prompted my inquiry in the first place !!

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ell, like most things in life......it depends. I don't know what specific gen & VR is in question here.. If 9N.2N with cut out, there is no voltage regulator, and output will go up into region of 20 volts and if run there long, the generator will get very hot as the Field is fed from inside the generator from its armature. Normal field current may be around 4 -5 amps. If output voltage doubles, field current doubles. Power (heat) goes up by the square of current, therefore think 4X normal or instead of 37 Watts, it may see 150 Watts! I expect that to be a problem after awhile. If newer system with a voltage regulator controlling field current, then IF all is functioning as normal, the VR will regulate the output to normal voltages. However, when unloaded, that VR is trying to control a generator capable of outputting several times normal voltage and my question would be, does it have the range capable of doing so? The mechanical VR controls by switching field current on-off-on at a rapid rate & for varying percentage of time to maintain an average output of a bit over 6 or 12 volts. This might look like 10v on for 60% of time and off 40%. However, of no load it may look like 18v on for 30% and off for 70%. Does VR have this range? Can its contacts tolerate switching the 3X current? Experience says, probably yes for at least a short period of time, but I have never tried to run like that & have never set up meters & oscilloscope to observe precisely what is going on under such circumstances. I don't think I would risk my own good working system to do this experiment. Maybe someone else's? As John said, battery cables have been momentarily disconnected for seconds many times in the past without known damage. Some of my thoughts & perhaps & maybes, etc.

(quoted from post at 10:26:57 05/07/21) I see 100s of engines ran with an alt and no battery connected. The only power is to the ECM from a remote source.

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ome alternator-reg designs are such that if they sense no battery voltage, they shut down , but others go to maximum output. Again , like diapers, ...it Depends!

John, Thanks. Are you still plunking the banjo? 5 string I assume. I recently fixed up a tenor banjo for a grand daughter. It plays just like a mandolin (same positions) with range same as viola and is very fun to play. I once tried a 5 string and found that 5th string MOSTLY in the way - the 4 string tenor is easier.

Some of you know I'm a classic type poster. I just looked at this on the modern view and see that if the quote function isn't used then it's harder to follow sequence on modern (or maybe I don't truly understand modern).

OK, I thought I had read this somewhere and I finally found it. This is in the owners manual for a Deere A ser 648000 and up. Notice it mentions magneto equipped tractors. In the tune up section it shows tuning up a magneto and also a distributor if so equipped. I thought the distributor came in later than this serial number but this proves me wrong.

Ron, this was taken at a Bus Nuts rally in Arcadia Florida in 2011. Ive gone downhill ever since lol

https://www.youtube.com/watch?v=EoPZE10wptE

John T
Banjo Ill Fly Away

Thanks, fixerupper I just had a hunch there could be some consequences from running a generator unloaded. Glad to see it written in a manual.

Sounds totally recognizable to me, John. Keep at it.