Ammeter for alternator

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Model T Ford Forum: Forum 2013: Ammeter for alternator
Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Sunday, May 05, 2013 - 05:39 pm:

I opted to replace the rusty non-functioning generator in my recently acquired 25 truck with a one wire 6 volt alternator from Larry Becker. The ammeter is incorrect and broken so I need a new one. Any suggestions or advice? Thanks for any input!!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dennis Halpin on Sunday, May 05, 2013 - 06:38 pm:

Amps are amps John, generator or alternator doesn't matter. Finding a good used ammeter on the 'net' (that you can't test ahead of time) is risky.
You can buy a new ammeter (from someplace like Langs) or you go to your local auto parts store and replace the ammeter with a voltmeter (like I did).
Note: My car was converted to 12 V before I bought it and replaced the (tweaked and tired) generator. Finding a voltmeter with a 6 volt scale on it, might not be that easy.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Sunday, May 05, 2013 - 07:40 pm:

Then why do the catalogs say "not recommended for use with an alternator"? I'm confused.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Sunday, May 05, 2013 - 08:18 pm:

Also, is any harm done by temporarily bypassing the ammeter and connecting both ammeter wires to the battery terminal on the switch so as to power the coils ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Sunday, May 05, 2013 - 08:25 pm:

John

No harm whatsoever in bypassing ammeter. Only difference will be that you won't have an ammeter!

Dennis is correct ... 6v, 12v, or 24v, ammeters don't care - they measure current not voltage. Any DC ammeter that shows more current on its maximum reading than you expect to flow through the circuit will work fine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Sunday, May 05, 2013 - 08:44 pm:

Bud, any idea why the caveat in the catalogs? I'm going to call Langs tomorrow to see if I can get an answer. Thanks for the input!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Sunday, May 05, 2013 - 08:58 pm:

Ammeters, in order to measure current must drop the voltage in order to measure current. For an ammeter that measures 5 - 10 amps that voltage drop will be miniscule, probably less than 0.1 volts.

The output of an alternator is closely regulated to keep the battery at full charge with typical driving (usually 14.3 - 14.5 volts, in a 6 volt system 7.15 - 7.25 volts).

They may be concerned that the voltage drop through the ammeter will provide less than optimal voltage to the battery.

That is the ONLY reason they would be concerned about an ammeter in the circuit ... and its nonsense!

Suggest you call Mr. Becker and see if he has a rational explanation !


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Sunday, May 05, 2013 - 09:10 pm:

John:

I have a Becker 6 volt alternator on the '26 for the last three years. No problems, and the ammeter, even with a low battery never showed a charge over 10 amps, quick charging alternator.
Mr. Becker is a quality vendor with quality items that work properly...... My $ 0.02 .


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Sunday, May 05, 2013 - 09:23 pm:

Just to be clear, I am not concerned about the alternator and am very pleased in my dealing with Mr. Becker. My reservation was about using an ammeter which was sold with a warning about being used with an alternator and not understanding why. While studying this issue I discovered the new Fun Projects unit and will check it out tomorrow. Thanks to all for the input!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By JohnH on Sunday, May 05, 2013 - 10:21 pm:

The voltage drop across the ammeter is no more than will be dropped across the wiring anyway.
My guess is that the higher possible output (~30A) from an alternator might be too much for the flimsy terminals of the repro ammeter and they're worried they might get cooked.
Electrically, however, there is no reason not to have an ammeter with an alternator.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Sunday, May 05, 2013 - 10:49 pm:

One significant reason that a Model T ammeter is not recommended for an alternator is that the T ammeter cam not handle the higher current output capacity of most alternators. They can burn out rather easily.

Be_Zero_Be


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Mikeska, Denver CO on Sunday, May 05, 2013 - 11:00 pm:

And when smoke starts rolling out from under the dash while you are out having fun...Well you may not be having anymore fun. Make sure the insurance has been paid up, carry a fire extinguisher and pray you can quickly disconnect the battery. Had it happen on a 27 Touring car with a stock generator. The new ammeters that the vendors sell for 26-27's are cr@p. If you have to use one use real brass nuts for the electrical connections and tighten them with a wrench.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Sunday, May 05, 2013 - 11:09 pm:

The new ammeters offered most likely have some electronic which don't like the high output of the alternator. The old fashioned ammeters have a meter in parallel with a shunt. The shunt handles the high current.

The alternator output varies from a negative 10 amps at low rpm to an output of 90 amps right after starting and then levels out to near zero as the battery gets a full charge. The ammeter needle disappears at the high outputs. It takes a little getting used to when you first put on your alternator.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Monday, May 06, 2013 - 01:48 am:

You are not likely to reach full rated output from an alt if you are driving it with the gen gear, which is at most 1.5 times crankshaft speed. The typical alt in moderns is driven at nearer 3 times crank speed, and that on a higher revving engine.

I prefer a voltmeter. Source near the battery is best. Any over 6.9 volts on a fully charged battery just goes to boil out the fluid.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, May 06, 2013 - 02:07 am:

The electrical system on a T is designed to handle 20 amps. Ignoring that and using an alternator is dangerous to the health of the wiring and ammeter. Scoff all you want to but there is no earthly reason to put an alternator on a T or A either for that matter since it too has only a 20 amp wiring system on it. Since I make the ammeter I simply don't want to have to deny warranty coverage on a burned out meter. There is no current limit on an alternator and burying the needle on any ammeter is running the meter beyond its rating and you will likely ruin it. Some people think that since they have not seen any smoke come out of their meter that everything is fine. An alternator is capable typically of putting out 750 watts of power but more importantly there is nothing inside of an alternator that limits its current output to a safe amount of 20 amps or less. The model T generator on the other hand has an adjustable third brush that allows you to set the maximum current that can be provided by the generator. The ammeter that we make is not frail and to date nobody has burned one out. I like it that way and don't support abuse of repro or original ammeters so I state that it is not recommended for use with alternators. The "more is better" concept just isn't valid when it comes to electrical charge current. The voltage drop of our ammeter is less than .05 volts at 20 amps and it uses #10 solid brass studs on it and solid brass nuts so there are no "flimsy" parts used anywhere in it. It is a conservative design and it is better than 1% accurate at full scale while originals were only 5% accurate. It is a quality instrument that I don't want to see abused. I fully admit to being a "mother hen" about my products but I have been that way my whole career so can't really change it. If you really believe an alternator is necessary and the way to go - that is fine by me but please use some other ammeter on it and I won't mind at all.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Schedler, Sacramento on Monday, May 06, 2013 - 06:14 pm:

I had to install and alternator in order to run my air-conditioner that has two 12v, 10 amp motors and the clutch. I have a 2 wire Nissan alternator run by the belt. My amp meter pegs out for a while after starting the engine but soon drops to 12 amps or less. So far so good and I'v had this set up for years now and all is well. I have to turn the alternator on and off though and it's not that convenient If I forget to turn it off I kill the battery. Should I install a reverse current relay?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, May 06, 2013 - 07:12 pm:

The problem with using an ammeter in an alternator circuit is twofold. First and most important you have no idea what charging voltage is being output by the alternator. The big problem with any alternators is overcharging. Battery failure is the result of either overcharging or undercharging. An ammeter does not help.

Second, any modern alternator is capable of 50 amps or more. As John correctly stated the Model T ammeter wiring harness is not tolerant of this sort of current. Fires and insurance claims result.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Schedler, Sacramento on Monday, May 06, 2013 - 07:38 pm:

Thanks guys. I'v not experienced any explosions, fire or smoke to this point (6+ years), so I'll keep on keeping on. My other car has all the right stuff and I have extras if I have to go back to original on my Fordor "touring" vehicle.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Schedler, Sacramento on Monday, May 06, 2013 - 07:44 pm:

I've not had a problem either. Vowels have a way of making me look stupid....Maybe they're right.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, May 06, 2013 - 07:59 pm:

When using an alternator on any old car that was originally equipped with a generator you need to upgrade the wire size to be capable of handling maximum alternator output. Fires and exploding batteries are a common result of poorly installed alternators with a seldom driven car.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, May 06, 2013 - 11:55 pm:

Hal:

Of course its your T so you can do as you wish. Not having a problem for years is not proof that all is well. One can play Russian Roulette with a gun having 300 cylinders and survive for a long time. Every time you "bury the ammeter" you are pushing it well beyond its ratings and sooner or later.....


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Tuesday, May 07, 2013 - 12:17 am:

The "melting current" for copper wire is approximately: (from Reference Data for Radio Engineers, Fourth Edition)

83 Amps for 18 gauge
166 Amps for 14 gauge
235 Amps for 12 gauge
333 Amps for 10 gauge

So if you have at least a 14 gauge copper wire, then you have some safety margin with an alternator. There is no question that driving the ammeter off scale is ammeter abuse.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Tuesday, May 07, 2013 - 12:34 am:

Ted:

So would anyone wire their house with 14 gauge and install a 150 amp breaker?

Melting point of wire is hardly a specification to use for safe wiring. It isn't where the wire melts that counts, it is where the insulation melts or ceases to work as an insulator and the wiring then begins to short out to ground in various places. This whole discussion is getting silly. A man has to do what he thinks is best but please don't try to tell me that it is perfectly safe - it isn't. It is still just a 20 amp system by design.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Borland. Bathurst. NSW. Australia. on Tuesday, May 07, 2013 - 01:13 am:

John has it right. Age also reduces the insulating capacity.

Peter


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Stitt-Southern Oregon on Tuesday, May 07, 2013 - 01:44 am:

Royce I really don't see overcharging problems with alternators and in the last 35 years we have done a lot of them. You make a good point however.
I am picky about where my regulators come from, and OE does not want overcharging issues.
To your point it may be inherent in single wire 10/12 SI alternators. They have no secondary voltage control and no true sense function. A drop in VR is common and they are poorly made. Wire in a diesel 21/22SI VR and you will not have a problem as they are in fact designed for one wire apps and control voltage output on alt's as large as 200 amps. Delco#1116390 WAI#D21 or D22/D33. These VRs have a stud that is wired back to the positive side of the rectifier unlike the drop in VRs most commonly used.
By the way if this style VR is used and you can find the "cube" that fits the 27SI that plugs into the back of the VR it has a red cap that can be rotated to change the voltage.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Schedler, Sacramento on Tuesday, May 07, 2013 - 01:44 am:

Thanks John. I respect you expertise on this subject and will take appropriate corrective action. Your posts are appreciated!!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Tuesday, May 07, 2013 - 08:40 am:

Hal,

I just share what is safe and intelligent to do to protect your investment. I've seen several alternator equipped Model T's fry their under dash wiring harnesses on tour. Had another one at last year's Texas T Party. He was lucky, it didn't consume the car. Just caused a ride on the vulture wagon.

The original design Model T wiring harness isn't capable of handling the current of any alternator that I know of. The ammeter is a weak point too but if it fails you just lose battery charging capability. It doesn't burn up the car.

Since a Model T ignition is not dependent on the battery this is just an annoyance has no effect on reliability if your magneto is functioning properly.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Tuesday, May 07, 2013 - 08:40 am:

Mike--are you saying the voltage regulator you mentioned would solve this problem? I gathered from this discussion that amperage is the problem. Does a VR control amperage? Pardon my ignorance, I'm trying to get this right since I already have the alternator. Would it work with a 6V one wire alt? Wired in between the Alt and ammeter?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Tuesday, May 07, 2013 - 09:28 am:

John

This is getting way over analyzed. Check with Mr. Becker - he can give you an estimate of the output of his alternator under worst case conditions (dead or nearly dead battery, lights on, etc.).

Probably in the 30 - 40 - 50 amp range, although at T engine speeds I would think it would be in the lower range.

The voltage regulator (contained in the alternator) will do a fine job just as it is.

Size the wire From the alternator to the battery accordingly, and size the ammeter accordingly and drive the darn thing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Tuesday, May 07, 2013 - 10:40 am:

Yeah Bud, I had just about reached that conclusion myself. Worst that can happen is the whole thing burns down and I have to find another one! I've seen too many touring T's with alternators to think it is very likely to be an issue. Not saying it can't happen, but lots of things can happen driving a T.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Tuesday, May 07, 2013 - 12:19 pm:

John R. presents a valid point (as usual). The T generator is capable of 120 Watts max. The alternator 750 Watts.

The alternator on modern cars has its output wired directly to the battery, not through an ammeter or instrument wiring.

The volt meter is wired in parallel (not carrying any current).

The generator passes its full output through the ammeter to the battery.

If one chooses to replace the generator with an alternator, then it is just good practice to wire it correctly, and replace the ammeter with a voltmeter again wired correctly.

Many don't follow this practice,I know, but a low or dead battery being charged with an alternator could stress the stock wiring and ammeter to the point of a catastrophic failure!

Not a risk I would be willing to accept, since the fix is so simple.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Schedler, Sacramento on Tuesday, May 07, 2013 - 04:28 pm:

I'm glad this thread got started. It may have saved the Eureka Springs Arkansas fire department a call when I go on the Hill Billy Tour in September. It's hard to admit that I DON'T know everything.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann, Blistrup, Denmark on Tuesday, May 07, 2013 - 05:18 pm:

I have another problem with the ampmeter and my consumers.
Regular 6V Model T generator with a well working Fun project VR, 2 x 35W headlights + 3x5W rear light, 3x21W stop light and traficators.
The latter use a significant amount of current to stay out in position, so when lights are on, traficator active and flashing and I press the brake at a red light the consumption is way beyond the 20 Amps. If I rev the engine I can get the discharge under 20 amps, but I am a little concerned for the nice Fun project Amp.meter I have.
I'm not that concerned about the wiring as the situation is only present for a couple of minutes.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Weir on Tuesday, May 07, 2013 - 05:55 pm:

@ Michael; I have two stop/turn signals on each side of my TT, as well as a high stop lite. They are LEDs and don't even show on an ammeter. Yes I'm now running a 12 V Texas T alternator that has a single wire output so I can Light up the Christmas Lights parades, as well as power my Son's laptop to run the wide band O2 sensor for experimentation.

I am sure that you can find 6V LEDs and use an electronic flasher from Radio Shack like I'm using.

Sincerely

Jim Weir


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Stitt-Southern Oregon on Tuesday, May 07, 2013 - 09:05 pm:

Hi John M,
I was addressing overcharging. As an alternator's VR only controls voltage not amperage. The wiring issue was addressed by John.
There is a drop-in VR that is designed for one wire systems and the design is predicated on the ease of assembly.
If overcharging is an issue the 21/22SI VR should solve the issue. The are "machine" sensed at the rectifier.
The point about the 200 amp alt controlled by the VR is that the field transistor is very heavy and can tolerate longer "on time." The off time is a cooling cycle.
I would avoid the drop in VR's. The failure rate is quite high imho.
BTW, think of an alternator like a wall plug. Constant 110V and it will supply all the amperage demand it can up to it fused capability.
I run a generator.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Tuesday, May 07, 2013 - 09:36 pm:

Thanks Mike, but its all too much for me.I ordered a 30 0 30 ammeter, I'll run 14 ga. wire, put a 20 amp fuse as recommended, cross my fingers and chug down the road!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Thursday, May 09, 2013 - 01:46 am:

Michael D>

The total red lights you have would seem to add up to about 10 or 11 amps. You might be able to reduce that load by 90% if you convert your rear tail lamps and stop lights to LED. What are "traficators" and why do they draw so much current? If they are arms that motor out and back then why do they draw current any other time? It might be a stupid question and perhaps others know what traficators are but I am not sure.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Stitt-Southern Oregon on Thursday, May 09, 2013 - 02:20 am:

Happy chugging John M., don't chug and drive.
Wasn't that Roger Miller, Chug a lug? lol


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Borland. Bathurst. NSW. Australia. on Thursday, May 09, 2013 - 03:47 am:

G'day John,
Traficators are directional indicators.

Peter


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Thursday, May 09, 2013 - 08:42 am:

John Manuel -

The 30 amp ammeter will likely survive, but again it won't tell you anything useful. The most important thing anyone needs to know about their alternator is what voltage it charges the battery. You can measure it with the engine running using a hand held voltmeter.

A correctly operating alternator produces 13.7 - 14.2 volts measured at the battery terminals with the engine operating at a high enough speed that no increase in voltage can be obtained.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Thursday, May 09, 2013 - 08:58 am:

That's why my car is equipped with a voltmeter, and not an ammeter.





That's it in the left lower of the Atwater-Kent coil box. You are probably the only one here to recognize that meter is from a 618M-2, Royce.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Thursday, May 09, 2013 - 10:31 am:

Royce, I have a 6 volt alternator and I have found a 60 amp ammeter. Now wire guage should be my only concern if I understand all this correctly. Right? And if voltage is the principle concern, why did the cars have ammeters? Educate me!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Thursday, May 09, 2013 - 10:54 am:

John,

An alternator can charge the battery at too high a voltage value. For example the 6 volt alternator output can be as high as 10 volts. The ammeter would show only the amperage. When the battery reached 10 volts the amperage shown would be zero. However your battery would be boiling.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Thursday, May 09, 2013 - 10:56 am:

Uh oh.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Thursday, May 09, 2013 - 11:20 am:

Again, why did millions of T's have ammeters. I don't pretend to know any thing about it, only asking. If the ammeter goes back to zero is the battery still being cooked?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Thursday, May 09, 2013 - 12:27 pm:

OK--the generator never puts out more than 6 volts and the alternator, even though only briefly, can run 10 volts and overheat the battery especially if it is old are severely discharged. I think I have it!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Walt Berdan, Bellevue, WA on Thursday, May 09, 2013 - 12:41 pm:

John,

Almost right. The generator with a voltage regulator will manage the voltage / power output of the generator. A T generator without a real voltage regulator (stock cutout or plain diode) will charge at a rate based on the setting of the 3rd brush, up to it's maximum output. You can most definitely cook a battery with a stock T generator if it doesn't have a real voltage regulator like the one John Regan makes.

Walt


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Thursday, May 09, 2013 - 12:53 pm:

Hal,

I think you had better alert the Eureka Springs Fire Department to be on call as there may be others, not privy to these posts, that have Model T's with alternators. Please trailer your T to Eureka Springs. I don't think driving it from California to Arkansas would be safe unless you crossed the desert at night.

Ted


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Stitt-Southern Oregon on Thursday, May 09, 2013 - 01:19 pm:

John M,
My guess is that in the early era electricity was not well understood by laypeople. Amp gauges provide about a step above an idiot light. It is either + or - and - is not charging.
When the industry switched to voltmeters to this very day people ask how to in interpret voltmeters.
I point out that it's like a gas gauge. 14V is a full tank at 12v you are on reserve.
To illustrate this for years folks with 60/70s Ford would show up regularly asking why their amp gauge didn't work. One guy came over from the dealership as they simply told him the amp gauge fills a hole in the dash....Yep. lol
I really don't see alternators with high voltage issues. If they are open circuit yes. It is the one thing the manufacturer avoids like the plague.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Thursday, May 09, 2013 - 02:11 pm:

Incredible amount of feedback on this post and I thank everyone who tried to help me with this quandary!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Thursday, May 09, 2013 - 02:23 pm:

I've come to expect crummy quality and be pleasantly surprised when good quality comes. I can't say who is selling the crummy alternators but they are not made in the USA. If any are made here is another question.

Just check voltage when you first install it to avoid a nasty surprise.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Thursday, May 09, 2013 - 07:39 pm:

John, I went looking for a succinct description of the three charging methods used in a T, but came up short. I bet John Regan had a good description of third brush and voltage regulated generation.

Basically, a generator is a fixed current output device. That current of zero to ten amps is governed by the adjustable position of the third brush in the stock T. You normally charge a six volt battery with the T generator, but it will charge a 12 volt battery, at reduced current. Third brush generators were used until WWII, AFAIK. My '39 Plymouth had a third brush gen.

Adding a voltage regulator to a generator converts it into a hybrid voltage/current output device. The Fun Projects VR moves the third brush electrically and automatically. It is a big step forward. Output of generators designed for a VR are governed by the VR controlling the current in the field winding, a simpler method.

Built into the design of an alternator is constant voltage output, regardless of current required. It will put out 6.9 volts all day long. When the battery is charged up to 6.9 volts, it won't demand more than a trickle of current, and won't be overcharged. Turn on the lights, and the alt keeps it all at 6.9 V.

There are subtle things going on, too, like higher voltage at lower temperatures to charge the battery faster after a heavy load start, but they are refinements of the basics.

Confession: I have always run 12v alternators, and have burned up several, but too lazy to move it out of the gen hole where it turns too slow and gets hardly any cooling air. If you're going to take full advantage of the power capability of an alternator, it needs to be spinning faster, and cooled with the fan it came with. Here's a good example:


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Friday, May 10, 2013 - 09:29 am:

From a link to an old tractor site on wiki:



These need to be re-drawn for our use, as they show positive ground, and the T doesn't have that handy switch for increasing the gen output when the lights are turned on. The external loads aren't shown, either.

Further to above, the third brush generator is really the wrong tool for the job. It generates a fixed amount of current, while the battery, lights, etc., need a fixed voltage, and variable current.

A practically discharged battery will show 6.0 volts. . A fully charged battery at rest after the surface charge dissipates, will be at 6.3 volts, (serendipitously (?) the same voltage as the filaments/heaters of most vacuum tubes.) . However, it takes 6.9 volts to fully charge the battery, the difference being called a surface charge. Applying much more than 6.9 volts will just boil the water out of the battery, causing corrosion on the terminals, etc. . As the battery approaches full charge, its current demand tapers off to a few milliamps.

Charge a full battery with the third brush generator set at 5 amps, and the voltage rises until it draws 5 amps, the 5 amps serving no function other than to boil battery fluid.

Turn on the lights that draw, say, 10 amps, and the generator still puts out only 5 amps, the other 5 amps coming out of the battery, and you see -5 A on the ammeter. As the battery discharges, the lights get dimmer.

Now you see why the Fun Projects voltage regulator that converts a Model T's third brush generator from a current source to a voltage source is such a boon to humanity. The battery is no longer over- or under- charged, you no longer have to re-water the battery or clean off the corrosion, and your lights don't go dim.

By now, it should be evident why Model Ts have ammeters. The ammeter tells you at what rate the battery is being charged/discharged. However, it does not tell you when the battery is fully charged, fully discharged, or in between. Ammeters continued in use after voltage regulators were adopted, as they still told you battery charge/discharge rate. Just a needle width positive deflection of the ammeter told you the battery was fully charged, and being kept at full charge.

It probably took the invention of zener diodes to make cheap voltmeters that would give you enough spread on the meter between 6.0 and 6.9 volts be really noticeable. Put a one volt meter in series with a 6 volt zener, and you have the full scale of the meter to tell you battery charge, which was your real goal all along.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Friday, May 10, 2013 - 01:42 pm:

Larry Becker's alternators are excellent and come with a lifetime warranty. As long as he's alive he will repair or replace a defective unit.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Micheal Crowe on Friday, May 10, 2013 - 07:00 pm:

How do you get ahold of Larry Becker?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Friday, May 10, 2013 - 09:19 pm:

For shitz and giggles, I hooked up my analog meter to observe the voltage of the Becker 6 volt alternator from start-up, stop and go traffic, steady road driving.

Battery has a few months of use, registered 5.8 volts at rest. After using the starter, voltage output from the alternator to the battery was 6.8, after some stop and go traffic, voltage was 6.3. During a steady speed drive, no lights or cross streets, observed voltage was 6.2 VDC.

The ammeter showed maximum current charge at about 7 amps , settling down to just a hair over "0". With headlights on bright,have double stop-tail lamp assemblies, needle showed -9 amp discharge briefly till the alternator kicked in showing "0" amps , while the voltage observed was about 6.5 VDC. Headlight bulbs are the original 21/21 CP bulbs.

Becker 6 volt alternator has been in use for 3 years, and I'm satisfied with it's quality.
And...... besides, when I called Becker's to order the alternator, they sent it along without and credit card payment, was asked to mail a check when unit was received. How's that for trusting old fashioned service ????

P.S. ... the purchase was three years ago, their payment policy may have changed ....

Bob Jablonski`


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Manuel, Lafayette, La. on Friday, May 10, 2013 - 09:29 pm:

No, still the same. I ordered and received before paying with no history of doing business with him. I asked him if he was sure he didn't want me to pre-pay and he declined, saying Model T guys are good people!! He is hard to get on the phone though. I understand that however. There are times I can hardly get any thing done with the incessant phone calls, especially when my office manager is out.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Friday, May 10, 2013 - 10:21 pm:

I think your meter is reading low by as much as half a volt, Bob. Readings should be taken at the battery, btw, if there is much current flow.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Saturday, May 11, 2013 - 06:54 am:

John:

Nice to hear Mr. Becker still has trust in his fellow T'ers.

RD:

Half-volt misread/meter error isn't that bad.... still ballpark? Same with script 20-20 ammeter ?


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