Generator Testing

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Model T Ford Forum: Forum 2013: Generator Testing
Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker on Wednesday, January 23, 2013 - 08:51 am:

I've read through the electrical system guidebook and was curious; can a 6v battery charger be used to test and set the brushes on a generator? Don't have a 6v battery yet, but I have a charger.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Wednesday, January 23, 2013 - 11:36 am:

What is the ampere output of the charger? A 6 amp or larger would probably work, 4 amp maybe, I wouldn't try anything smaller than that.
Give it a try, what have you got to lose?


Top of pagePrevious messageNext messageBottom of page Link to this message  By William Rowles on Wednesday, January 23, 2013 - 11:48 am:

I think the generator needs a place to pump the electrons to......a reservoir at a certain voltage. The charger is not a reservoir, it is a source of electrons , so I am afraid the two sources will "fight" each other and the loser will be damaged. I would get the battery installed and connected to the generator before trying to pump electrons (run it). Maybe an electrical engineer or electric/electronic technician will join this discussion......


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker on Wednesday, January 23, 2013 - 12:01 pm:

The charger is a small one, not really intended for such a purpose. I think I'll play it safe and simply buy a 6v battery to test it and set the neutral point. Don't have the engine in the car yet, so I won't be able to set the third brush position. Just want to get the generator squared-away. Thanks for the input.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Vaughn on Wednesday, January 23, 2013 - 12:12 pm:

Yes you can use a 6 amp charger to set up your generator to find "neutral" with the 3rd brush lifted off of the armature and the 4 screws loose that hold the brush plate. Rotate the brush plate with the generator energized and it will try to motor one direction or the other, set the brush plate so that it is in the neutral position and de-energize the generator. After you tighten the screws on the brush plate again you can test for "neutral" and then drop the 3rd brush onto the armature you can test to see that the unit then "motors".


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Wednesday, January 23, 2013 - 01:14 pm:

A warning!

I was able to repair a battery charger for a friend who destroyed it while using it as a power source to test some things. What happened? Battery chargers assume that they are going to be used to charge a battery and they have little or no protection from transient voltages that normally cannot come out of a battery whether it is dead or alive. Thus if the load you connect your battery charger to has any inductance in it as part of the load - that inductance can produce a very high inductive "kick" back into the charger and cause its rectifier(s) to short. It really doesn't take much inductance to produce a spike of voltage over 100 volts that will be beyond the voltage rating of common devices used in a battery charger (remember the charger is for 6 or 12). If you value your charger - use it on batteries only. You might get lucky a few times but you you might not get lucky even once. Generator is a motor when you power it up and as such it is full of inductance and spikes as are ignition coils and other such devices. USE A BATTERY to test here and save your charger. Your mileage may vary.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker on Wednesday, January 23, 2013 - 02:45 pm:

Thanks, John. I'll do just that. I set my neutral point with a 6v DC power supply, and the draw was 3.5 amps. Rotation was clockwise looking at it from the commutator end. Hopefully that's correct.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker on Thursday, January 24, 2013 - 03:36 pm:

I'd like to spin test my generator to see if it will function. When spin testing the generator, what are the proper connections using a multi-meter (not digital) to check charging rate? I know, it's best to set the third brush with the generator in the car, and I'll do that when I can, but that's not possible right now. I just want to check to see if the generator will generate a charge, or if it needs a more in-depth overhaul. It runs correctly as a motor; clockwise looking at the gear end. Thanks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Thursday, January 24, 2013 - 04:41 pm:

Dave:

Its not a case of "best way" to set charging rate but rather the only CORRECT WAY to set the charging rate. Any test you devise for "off the car" is not going to worth much other than motoring the generator which just tells you that likely the armature and fields are working at least somewhat. I am one of those "do it once - do it right" kind of people and think that the key to the whole electrical system working right is a good working generator so I would be checking it out rather thoroughly rather than just wanting to see if it functions - whatever that means.

BTW the use a a 6V power supply to motor the generator runs somewhat the same risks of using a 6V battery charger depending on the filtering capability of the power supply. Usually a well designed power supply will have a specification on maximum inductive load for the same reason I mentioned about the battery charger but that spec is likely buried in the fine print. There is rarely an easy to find inductive load specification on a thing being powered up so its just a risk that you either take or don't. I don't risk my good lab grade power supply for such things.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker on Thursday, January 24, 2013 - 06:27 pm:

Thanks for the sound advice, again. I know when to listen, and truly appreciate your help.


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