I think the answer to this weeks puzzler was incorrect! It was about the guy who was in the middle of nowhere with a dead battery and some tools. The answer was to take the belt from the alternator and run it around the drill he had and run the drill until the battery was charged. It is my understanding that an alternator needs a little bit of current in its field in order to generate electricity. Therefore no amount of spinning that alternator with a dead battery will produce ANY amount of current. Now if it was a generator, that’s a different story. But to my knowledge, only old VW’s used generators.
You’re right, but maybe they’d claim the battery couldn’t start the car, but still had a few volts that might have been enough to get the alternator going.
Like tom or ray said would the ignition need to be on is the big question. If the alternator turns it does not care if a belt or a drill makes it turn around to do it’s duty, as it turns it creates the charge.
A live cell phone can help. I used to have a spare car battery in the back of my truck.
Alternators have enough residual magnetism to be able to self energize if the alternator is spun fast enough.
RE: Alternators have enough residual magnetism to be able to self energize if the alternator is spun fast enough.
That goes against my electrical training (years ago). Generators are able to “self-excite” because of the permanent magnets. If what you’re saying is true, what is it in an alternator that give it the ability to ‘self-excite’?
I don’t believe a battery drill motor could turn the alternator fast enough or long enough.
I also don’t go for the self exciting alternator,but my mind is open to a explaniation.
Well I don’t think they specified whether the drill was a cordless or a wired 120v drill. Either way he had the gas powered 120v generator to keep the drill running. I have no idea how much energy is required to turn an alternator at full load. Sounds like it could work (if the battery wasn’t dead as they said it was) as even cordless drills have quite a bit of torque… Now I’m kind of skeptical that if it was a cordless, it would have enough juice to recharge the truck battery enough to start the truck before the cordless drill ran out. He could have recharged the battery with his 120v generator, but that’s like at least a half hour to an hour charge, and they said it was almost dark out.
I missed the puzzler, however I’m extremely skeptical that even if run until drained a cordless drill battery could, after subtracting all the losses from operating the drill, the V belt, and spinning the alternator, transfer enough power to charge a dead car battery sufficient to turn over the engine…both turn it with the starter and provide sufficient power for spark.
Remember that the drill battery cannot through any conveyance charge the car battery with more power than it itself has. Similarly, the engine’s alternator cannot create electrical energy beyond the amount of mechanical energy being transferred to it by the drill.
But if I were stuck in the middle of nowhere I’d probably try it anyway…
This puzzler would make a great experiment and not cost a lot to try. The question is “Can the drill turn the alternator fast enough?” I was thinking the best approach would be to duct tape the chuck of the drill to the pulley of the alternator. But can you get the drill on axis, in front of the pulley to be effectively?
So if any one has a late model Chevy, Ford, or Toyota pickup, leave the head lights on long enough to run the battery down; ship the alternator belt; and try using a drill to charge the battery. Does that work? Does the ignition switch need to be ‘on’ to make it work?
Post back your results. I suspect that there is no way to use the drill off axis to turn the alternator fast enough. IMHO a modern single wire alternator with a diode trio powering the internal voltage regulator will self excite. There is enough residual magnetism in the rotor field pieces. But I could be wrong.
Without intending to repeat myself, I repeat…
The drill cannot through any conveyance charge the car battery with more potential that the drill battery itself contains. Subtract the losses from the mechanical systems involved in using the alternator to do it and the problem is even bigger.
In short, if the drill battery cannot by itself directly start the engine, then it stands to reason that it cannot give the car battery enough potential to start the engine. Moving the potential from the drill battery to the car battery using the alternator does not solve the basic problem. It just takes power away due to losses from the mechanicals of the drill, belt operation, and alternator.
Right, but it’s not a battery-powered drill, right? They ‘plug it into the generator’.
Correct my specs, 3/8 120V drill motor 1/3hp 1000RPM or? I belt HP loss 5-7hp?. Coaxing 10amps out of that alternator (which I consider a min charge amperage) will require you to maintain that 1000RPM, and you will have to spin that drill for what, 1hr?. Then perhaps the batterys charge will be enough for 4 ten second cranks? A lot depends on the batterys health.
I guess I didn’t see the part about having a 120VAC generator. I assumed “basic tools” as meaning perhaps a cordless drill. I think of a basic tool as fitting in a toolbox or toolbelt.
I also recognized in the thread the point of the alternator needing some battery juice to provide a field in order to function. Copper coils with no current flow whatsoever have no field and induce nothing. Except perhaps a false sense of security.
Either way, I have my doubts.
Get a trashcan and some spare iron rebar lying around the site. bend the iron into a loop taking care to ensure connectivity with the duct tape, split the jumper cable in half, run 18 loops around the loop on the generator source side and two loops on the car side. Submerge the loop and coils in the trashcan with the olive oil for cooling. Run the generator at 110 and you’ll get approx 12.2 volts AC on the car side. attach the car side to the battery and charge away, you’ll almost 10x the available current as well. Problem solved.
Apart from the other problems with this approach, you can’t charge a battery from AC.
Then he made a full-wave bridge rectifier with twigs and paint. What else is incorrect about it?
Someone has been watching McGuiver again…
The field windings of an alternator will use copper or aluminum wire, probably aluminum, wound around an iron core. The iron is actually silicon steel cut into thin layers to reduce what is called core loss. Core loss is the reluctance (or resistance) to develop a magnetic field.
There are two main contributors to core loss, hysteresis and eddy currents. To reduce eddy currents, the core is made up of thin laminates instead of a solid piece of iron. Hysteresis comes from the residual magnetism left over from the previous half cycle. This is a problem in transformers but not in the field core of the alternator since the field coil is fed by DC current.
Anyway, the short answer is that the core retains a small bit of magnetism. Is it enough to self excite the alternator, I doubt it but maybe.
A healthy battery that has been drained will create some current through chemical reaction up to the point that the battery is no longer healthy, that is permanently dead. It will provide enough current to excite the field coil. A heavy duty drill attached to a field generator will certainly be able to power an alternator to recharge a car battery. And a healthy modern truck will only need few seconds of cranking power to start.