Alternator Rotation Direction

[jj]

I am posting in this forum because i am dealing with a GM alternator. Simply, does an internally regulated GM alternator, as found on the CUCV, care what direction it turns? I have had a homemade "battery charger" made from such an alternator, driven by an old (i mean OLD) washing machine motor. The driver is on its last gasp, the replacement i've scrounged turns in the opposite direction and does not seem to be reversible. Any opinions?

 

[cornrichard]

I can't answer the reversible question. I have used some non reversible roller pumps in the past. If they were the wrong rotation I just mounted them with the pulley side turned around. You have to build a adapter plate. If your system is a homebrew that is usually not a big deal.

 

[doghead]

The cooling fan is the only "directional" item.

 

[gringeltaube]

.... and barely "directional", for the open style fan.

G.

 

[mistaken1]

The should produce power running in either direction assuming the RPMs are in the range the designers intended. Could be issues with nuts and cooling fans that are designed for only one direction of rotation.

I'm too slow ......

 

[supermechanic]

Shouldn't make a difference.
Washing machine motor is fractional horsepower.
Alternator won't be able to make enough internal heat with such a small driver to care if the fan is going 'wrong way'.
Pulley is a pressed fit to shaft, not much chance of pulley nut screwing itself loose.

 

[FireFighterHill]

Im curious as to the purpose of this charging rig you have made. Wouldn't it be easier, safer, better for the battery being charged, and less power used to have a actual plug in no moving parts battery charger?

 

[WillWagner]

Maybe a hot start? An alternator putting 90-100-110 amps and 14volts into a low or dead battery will be faster than using a charger even in crank assist. It's no more unsafe than if you were to push start a dead vehicle and the on board alt started charging. A hot start will put enough voltage into a dead battery(ies) to start the vehicle in about a minuite. I had one made with an old briggs engine, it got loaned out and never came back.

 

[FireFighterHill]

I could see using it in a pinch, but by using a alternator to charge a dead battery you shorten the life of the battery and the alternator.

 

[WillWagner]

That's all it's for, getting a dead vehicle started so it can be moved. In the repair industry, it seems trucks will start each and every day for the operator, but when the vehicle is brought in for a service event, it goes dead. A hot start is a fast way to get a truck running if it's dead, especially if the cost to the customer is upwards of $2.00 a min!

 

[jj]

Im curious as to the purpose of this charging rig you have made. Wouldn't it be easier, safer, better for the battery being charged, and less power used to have a actual plug in no moving parts battery charger?

Probably. But, those things cost real money. The stuff i threw together was already here. I have used this "device" to keep idle batteries intermittently charged. It is driven by a 1/4 horse electric motor of probably 60 years of age. The current alternator is a 66 amp internally regulated from probably 1982, or so. The motor gets to hot to touch after about twenty minutes, so it must be used under constant supervision. As the thing requires its own charged battery for excitation, it also makes a useful "hot start" device, too. It makes a pretty effective power supply for cranking an engine during compression testing, as the starter sees a constant voltage throughout the testing.

Turning the new non-reversible motor around would do the trick, but i want to try a direct coupling between the shafts. Something like a Lovejoy coupling. The new motor is higher horsepower and should drive the alternator adequately without a speed change from a pulley.

 

[rlwm211]

The equation of amps produced is directly associated the amount of power the Alternator is getting. Figure a 12 volt alternator is putting out 60 amps. That times 13.8 volts = 828 watts or volt amps of power.

Lets say the washing machine motor is 1/2 HP. According to the resources I can find, this is equal to 1/2 of 746 watts = 373 watts based on the standard number of watts 1 horsepower equals.

Not even figuring in losses and inefficiencies you will be able to take perhaps 25 amps of 13.8 power to charge the batteries you want to fast charge.

One redeeming feature of electric motors is that the highest torque is typically produced at the slowest RPMs. It should be pretty easy to tell how hard the alternator is working based on how slow the motor is turning it without a complete stall. If you gear down the Alternator by turning the motor faster and the alternator slower it will continue making power but at a lower level.

Personally if it were me, I would find a horizontal shaft gas motor of at least 3 HP and use that as it will probably be enough to produce as much as the alternator is capable of.

Use a big motor like a 12 HP and you can set up your pulleys so the gas engine is turning 1400-1600 and the alternator at max output and have a much quieter operation.

So, in conclusion, it will work....maybe not quite as much as you hope but it will work to use the washing machine motor to spin the alternator.

In a car typically the alternator is turning 10 times as fast as the crankshaft. Just thought this may be helpful as the steady speed of 3300 is pretty much what the alternator sees at idle and maybe lower than that.

 

[FireFighterHill]

If you watch the circulars in the newspaper or in your mail you can find a cheap (around 20 dollars) charger/maintainer from autozone or discount auto. I just picked one up for 26 bucks from autozone cause Ive misplaced my Deltran Battery Tender, it goes for 60 bucks. While it wont start a car it will do a better job of maintaining batteries.

 

[WillWagner]

What if you stuff isn't close to an outlet to plug it in? Not all equip is garage trained, my deuce constantly makes it's mark where it sits. I've tried to train it but it's stubborn, so it stays outside. Bad, bad deuce!!

 

[rlwm211]

Hey, you can use a slave cable to power a 24 volt motor to run the alternator and then use that to jump your deuce......

This is, of course, circular electrical power theory!!!

 

[plym49]

The OP asked can it run backwards, not should should he do this at all.

There are a lot of ways to skin a cat, and just because what he has set up might not be optimal, it clearly works for what he does with it.

Yes, the alternator can spin backwards, and just as DH originally pointed out, only the fan is affected. Since you are using the setup intermittently and with the components exposed (and not buried in a hot engine compartment), this won't matter.

For the record, some older Ferarris and other exotics mounted the accessories backwards at the front of the engine for more efficient use of space. They used Plain Old Alternators and they spun backwards.

 

[Tow4]

The fan is the only potentially directional component. Most are centrifugal so they can go ether direction with no problem.

To spin a 60 amp or more alternator fast enough to produce rated output you will need a big motor. If you look inside a Jimco or similar alternator/generator tester you will find at least a 15 HP electric motor.

With all that said, I built a small alternator/generator with a 3 HP horizontal shaft BS gas engine and a old Delco 10SI alternator. I don't think it will do more than about 12 AMPs before the alternator will stall the engine if the battery is very low. The 10SI uses an external regulator so I put an adjustable regulator on it so I could limit it to about 8 AMPs.

You can still charge a battery pretty fast if you don't have access to A/C power or can't get a vehicle close to jump start; but it won't be like it's hooked to a vehicle with the engine running.

 

[jj]

TWELVE HORSEPOWER! FIFTEEN HORSEPOWER!! My physics book says watts equals volts times amps. So my 66amp alternator at 14.8volts makes less than 1000watts. ONE horsepower is 746watts, so, ignoreing thermodynamics, i should get the full output of the alernator from a 1-1/3HP motor. Yeah, i know it won't work out quite that way, but i surely do not need twelve or fifteen horsepower to drive a measly 66amps! Apparently, the only drawback to spinning the thing backwards is the wrong direction of the cooling fan integral to the alternator as pointed out by Mr.Doghead. I hadn't ever thought about that as the current driver does not make enough steam to make the alternator make enough heat to need cooling. The new driver won't either. Question answered. Thank you all, Goodnight.

 

[Tow4]

HA, HA, 1 and 1/3 HP! Good luck with that jj. Maybe if you can make that 1 and 1/3 HP at 12000 rpm. I think you will find that to turn that alternator fast enough with a B&S to make full output you will need about 5 HP. I am talking about driving the alternator with a lawn mower type engine, right?

In all seriousness, you can run your 60AMP 24V alternator (talking MV here) on less than 15HP you also know that heat, drive losses, the fan, etc. take more HP.

I think the problem with your HP calculation is the alternator's driven speed. You are talking HP at the alternator at the optimum rpm with no losses considered. I'm talking HP at the drive engine, in the real world.

A car alternator is full load at 6000 rpm. That 6000 rpm is crank rpm so you can figure out the alternator rpm based on the pulley diameters. A typical automotive alternator is designed for 12000 rpm. That is a 2:1 drive ratio typically. Some will do more but I don't remember specifics.

The Leece-Neville or Prestolite on the Deuce is going to be driven at a different ratio because a diesel is not going to turn 6000 rpm. I haven't checked to see the difference in crank and alternator pulleys on the multi-fuel. My guess is the alternator is spun at least 2:1 and maybe 3:1 or more of the crank speed.

In a nut shell, the alternator has to be driven at the optimum rpm for full output. If the alternator has to be over driven because the drive motor or engine can't turn that fast. then you need more engine or motor HP because of drive losses.

Well, we got pretty far from what the OP was asking.

TWELVE HORSEPOWER! FIFTEEN HORSEPOWER!! My physics book says watts equals volts times amps. So my 66amp alternator at 14.8volts makes less than 1000watts. ONE horsepower is 746watts, so, ignoreing thermodynamics, i should get the full output of the alernator from a 1-1/3HP motor. Yeah, i know it won't work out quite that way, but i surely do not need twelve or fifteen horsepower to drive a measly 66amps!