The Stovebolt Site Forums The Shop Area The Electrical Bay Generator not working???

I have to charge my battery after I start my truck once or twice because it gets low. Is there a way to tell if my generator is working or not? I seem to remember someone telling me that if you disconnect the battery while the truck is running it SHOULD keep running, but I'm not sure.

I just had to have my generator rebuilt. When I hook a voltmeter across the battery with the engine runing the voltage goes from about 11.5 volts to 13 volts as I increase the revs of the motor.
Hope that helps.
Bill
Tempe, AZ

Aha! I couldn't remember who said that! Never would have guessed it was you though, 54 Tow. Thanks for the info Yel 53 Chevy PU. Oh, and if someone is going to ask me about the voltage regulator, I know it's getting current to it because when I was repolarizing(or trying to do as I have no idea if the generator is good, but I was doing this according to the manual)the generator, I used a voltage meter(one with a light, probe, and a negative clamp) as a lead because I couldn't find a wire to use, and it lit up the meter light.

Generator definitely doesn't work good. Unhooked battery and it almost died, before I put the cable back on.

Hook a volt meter across the bat or the B term on the regulator. It will show about 6 volts. Start & rev the engine. The voltage should go up. If it doesn,t disconnect the F wire from the reg & ground it. Rev the engine. If the voltage goes up the gen is OK & the reg or circuit is bad. If it doesn,t the gen is bad.

Ok, will try that.

Yep, generator is bad. Voltage didn't go up at all. It stayed the same.

Well, now I'm not sure if it is bad or not. Due to me misunderstanding the '50's tech I didn't really know that the generator would charge the battery only if it got below a certain point or accessories or lights were on. Apparently it WAS NOT(not yelling) working when I tried this, but I noticed today when I rev the engine and there is a noticeable decrease in amperage(lights on) all I have to do is rev the engine and the needle moves back to the middle and slightly to "C." So now, it appears to be working and I checked the battery with a battery tester and it shows 75% and it was probably below that before.

jdl,
heres just some knowlege i gained over the years, Ive been riding an workin on old Harleys all my life it seems and with a generator on most, it takes considerably more juice to start the engine than a generator can replace in a short run,
Old Sportserts with electric start took a good 10 miles of riding to get the battery back to its state before starting.
hence since you are tinkerin and starting your truck for short durations you are probably just not running the truck long enough at operationg speed for the generator to replace the charge you burnt to start up the motor.
If you rev the motor and your gauge is sayin it is charging it most likely is ..you just cant get her out on the road to run her a few miles at operating RPM's to replace the charge.
I think you get her road worthy youll be OK.
for now doing your testing and troubleshooting I would just throw the battery charger to it when the battery seems week.
Tim

Checking battery terminal voltage only works when you're running a good generator against a fully-charged battery, particularly on a 6-volt system. If the battery is low, the voltage required to charge it will also be low. A generator is regulated for current outpuit, as well as voltage, and most 6-volt current regulators are set at 25 amps or so. It will take a long time to recharge a low 6-volt using the generator, many miles of highway-speed driving.

If you've got a low-amperage battery charger, run it overnight every few weeks until you are able to drive the truck on a regular basis. Just be sure to check the water level in the cells before you attach the charger. NEVER allow the water level to get below the tops of the cell plates. Add only clean water, never acid, to a battery. It doesn't have to be distilled water, but the bottled water sold for steam irons or deionozed drinking water is great for battery filling.
Jerry

Yep Hotrod, what you said in the last paragraph is basically what I have been doing. I checked it with a battery charge checker(looks like a dropper with markings on it, just in case there are different checkers out there) and it was 75% before I started it an ran it for around 20 minutes(while driving it around the yard.

SW, that's good to know. My worrying over whether it is charging or not was that when I revved up the engine at first(now I can tell that it is) that the needle moved so slowly that I couldn't tell if it was moving or not.

Jerry,

I will admit I don't understand the finer points of a voltage regulator. If the charging system is in first class shape, why doesn't it put the maximum amount of charge out against a 6 volt battery that is partially discharged.

It seems like it would output its max at first, then taper off as the battery voltage came up, ending up with just a trickle..not so!

Stuart

I don't understand either. I have my shop manual here and it say the exact opposite of what you said, Jerry. It says "With a Low Battery and a Low or No Charging Rate check the entire charging circuit for corroded battery terminals, loose or corroded ground strap, and frayed or damaged wires. The high resistance resulting from these conditions will prevent normal charge from reaching the battery. If the entire charging circuit is in good condition, then either the regulator or generator is at fault." So, what's what?

"low or no" charging rate is the key point in that troubleshooting bit - "low" means below the normal rate set on the regulator, which takes into account the max rate of charge that doesn't boil away the water in the battery .... you can't recharge a low battery real quick

if you have a normally operating system and you do something [leave the lights on] to really run the battery down, when the engine starts the ammeter will swing hard to charge [usually not all the way, but over half], but immediately, or quickly, it'll jump lower, and stay there for awhile before slowly starting to move back to neutral ... the regulator has sensed how low the battery is [feedback] and is controlling the rate of charge

Bill

AHA!!! I understand! Just to get this straight, this is what I now interpret the above as: The lower the battery voltage, the lower the generator output back to the battery is, and as the battery gets charged more, the higher the generator output to the battery gets, until the regulator senses that the battery is charged and shuts the generator output(at the regulator) off from the battery.
Hopefully that is right and now me and Stuart can understand!

OK- - - -it's time for "voltage regulators 101"- - -or you could just read the article I wrote in the tech tips section. There are three units inside the regulator that's commonly used with a DC generator. The cutout relay is just an on-off switch that disconnects the battery from the generator with the engine off to prevent the battery from discharging back through the generator. If that unit sticks, it's disaster time, with both the generator and regulator, plus the wiring, sometimes, going up in smoke or flames. The cutout closes when the generator voltage rises to a little above battery voltage, resulting in a flow of current from the generator to the battery.

If the battery is low, the generator will go to its full output to try to recharge the battery quickly. A generator can produce very high current flow under these circumstances, so it must be protected by the current regulator. This is the unit in the regulator with big, heavy windings and a set of points to interrupt the field current and reduce generator output anytime the current rises too high. High-current situations result in LOW voltage, because the resistance of the battery is low. As the battery increases in charge, the voltage rises, and the current drops. The current regulator stops working, and the third unit, the "voltage regulator" takes over. The voltage regulator setting is usually about 1.5 volt higher than the battrery voltage, so a generator charging against a fully-charged 6 volt battery will be regulated at about 7.5 volts. This prevents overcharging the battery. 12 volt regulators are set at around 14.5 volts or slightly more.

Hope this helps!
Jerry

jdl,

Stuart doesn't understand yet! My flawed logic would tell me that the 'empty' battery would 'fill' quite fast at first, tapering to very slow as it reached 'full'.

If you watch the ammeter on a battery charger, or even your ammeter equipped truck, the charge rate goes from high to low as the battery is 'filled', or charged. As the potential in the battery reaches the output capacity of the charging device, the rate of charge slows. Maybe the generator/voltage regulator deal the Jerry explained works differently, I don't know.

Stuart

Stuart, your logic is right on! A discharged battery will accept enough current flow to destroy a generator, so it must be current-limited to prevent it from burning itself out. An alternator is self-regulating on current, so the current regulator is not requirted.

To get an accurate voltage regulator adjustment, the charge current to the battery must be very low. That's accomplished by only adjusting the regulator when the battery is fully charged, or inserting a resistance into the charging circuit. The old Sun generator/regulator testers used to have a 1/4 ohm resistor we could put in series with the battery to simulate full charge. Then we could make an accurate adjustment of the voltage regulator. Someone who is checking battery terminal voltage while the generator is recharging a low battery will get a too-low reading that mkaes him believe the generator output is incorrect. The reading will be slightly above 6 volts, but not the 7.5 it's supposed to be, because it's only requiring that amount of voltage to refill the battery. it's like pumping water into a nearly-empty storage tank. The pump doesn't need much pressure to start the tank filling, but as the water level rises, the pressure goes up. The generator is the "pump", and tha battery is the "tank". It takes a higher voltage to force more charge into a well-charged battery.
Jerry

It's the same reason a 2A, or trickle charge, is better than a 6A charge; right?

Jerry,


Thank you, now I see the light!


Stuart

Ok Hotrod, I'm clear on this, you can keep on tutoring atomarc now. At least I understand this and at least part of my theory was correct.

54, a 2A charge will maintain a battery that's not used frequently, without boiling the water away. To actually recharge a low battery, a 6 to 10 amp charge is better. Once the battery is up to full capacity, then cut back to the 2A maintenence charge. High-rate "boost charging" is rough on batteries. I use a "smart charger" on my boat batteries, one that cycles on and off as necessary to keep the batteries hot without cooking them.
Jerry

Thank you, Jerry.

Is the smart charger similar to a float charger? I like the idea of having a "regulated" charge.
I've had a battery explode after leaving it on a trickle charger too long.
I mistakenly left the charger under a partially closed hood.
The charger became the ignition source for the Hydrogen...
Boom!

I got a "smart charger" from Walmart for $30. It can charge 6 or 12v and has a 2/4/6 amp setting. Works good and when the battery is charged it switches to 2 amp to float charge the battery. To answer your question yes it is similar, if not the same.