Amp Gauge

[donchiotos]

If you have a one wire alternator rated at 60 amps. Should you also have an amp meter rated at the same current? Or can you use a 30 amp gauge? I think this alternator rating is at 6000 rps, so the alternator will vary its output to load and rpms. Please set me straight on this question. Thanks

 

[PROCRAFT]

If you have a one wire alternator rated at 60 amps. Should you also have an amp meter rated at the same current? Or can you use a 30 amp gauge? I think this alternator rating is at 6000 rps, so the alternator will vary its output to load and rpms. Please set me straight on this question. Thanks

Use a volt meter and be done with it.

 

[spmdr]

First off, just because an Alternator is RATED at 60 amps does NOT mean it will NOT put out more current.

Alternators do not have current limiters as any part of the regulation process.

They are regulated for voltage only, and usually hold that level at idle, if not too heavily loaded.

Alternator current ratings are what they can safely provide.

Alternators are usually protected from too much current by a fuesable link output connection wire.


Voltmeters are less problematic (than AMP meters).

A GOOD "NOT Charging" light is most useful.

The bottom line is you CAN use a lower amp gauge than charging system capacity, just be prepared for wild meter swings.

DW

 

[Tom H]

The Alternator will most likely put out more than the 30 Amps through your ammeter only during the first minute or so after starting, as it recharges your battery, and your ammeter will peg. On mine, it often sticks on the peg until I tap on it. Understand that the ammeter does not measure how many amps the Alternator (or generator) is putting out. It measures how much current is going In or Out of your battery. I think most ammeters will not be damaged by current double its full scale value. If they were that fragile, they would fail every time there was an accidental short in the "Brown circuit" of an Alpine. And I actually prefer keeping the 30 Amp ammeter as it provides better resolution of the current. I can do some simple tests on my car with the car not running. I can turn on the headlights and see the needle move a little neg, turn on the blower, wiper, radio, driving lights, etc and see how much current each one ( or all of them) draws. Maybe the needle moves 1/4 scale neg, that means about 7.5 A. But if I had a 60 Amp ammeter, it would only move 1/8 of the scale. Harder to get much information from such small movement.

Tom

 

[RootesRooter]

I've read elsewhere that its hard to overload an ammeter, but you can damage the needle from it repeatedly slamming into the stop.

I've got a 50-amp Lucas ammeter installed with a a 60-amp Hitachi alternator. I have to rev it initially just to get the needle to budge, then it shoots over and pegs for several seconds. I've started turning on the headlights and blower before I rev it, which keeps the needle just short of the stop.

 

[belmateo]

If you don't want to fry your electrical system. Get rid of the amp meter and install a volt meter instead. Less chance of fire and other destruction.

 

[RootesRooter]

I like knowing how my charging system is performing, thank you

 

[Tom H]

A voltmeter can tell just about everything that an ammeter will. Just requires a little more judgement/interpretation. But I also have no issues with an ammeter. I don't see any added danger of fire or frying the electrical system. Wiring is a bit simpler with a voltmeter, if you were starting from scratch. But changing from ammeter to voltmeter is, of course, not simpler than leaving it as is.

 

[belmateo]

I like knowing how my charging system is performing, thank you

A voltmeter and ammeter are to an electrical system what a pressure gauge and a flow gauge are to an oil pressure system: A voltmeter measures electrical pressure in volts; an ammeter measures electrical flow in amps. "Pressure" or volts is a much more useful indication than "flow" or amps.

 

[RootesRooter]

Volts are more of a static, after-the-fact measurement, that don't offer clues when the driver eventually notices that the needle has deviated from the norm. Useful to a point, but I prefer to know how much flow there is, positive or negative, in real time. Ideally, I'd have both gauges.

 

[belmateo]

You are right as an amp gauge will tell you in real time what is going on, the needle typically moves around alot depending on the load and rpm.

 

[MikeH]

I liked having an amp gauge in my 71 Pinto. I could always verify my brake lights were working by the needle deflection when I pushed the peddle.

 

[Bill Blue]

I like volt meters. They give you an accurate assessment of the condition of the battery each time the ignition is turned on. Contrary to what a lot of amp meter lovers say, they also give a clue as to how hard the alternator is working. It does take careful observation as the meter deflections are not large. I am disappointed by their durability. I have replaced my VDO "Visions" voltmeter three times. That may be more of a reflection on the VDO gauge than voltmeters as I' also replaced the oil pressure and temperature gauges three times.

Bill

 

[Alpine 1789]

Having had both, all things being equal, I would rather have an amp meter. However, all things aren't equal and my amp meter was very close to starting a fire due to a loose connection that was only discovered accidentally. I will stick with volt meters from now on, especially now that matching ones are available.

 

[hartmandm]

Volts are more of a static, after-the-fact measurement, that don't offer clues when the driver eventually notices that the needle has deviated from the norm. Useful to a point, but I prefer to know how much flow there is, positive or negative, in real time. Ideally, I'd have both gauges.

I have an ammeter and use an Innova 3721 in my cigar lighter for the voltmeter when desired.




Mike

 

[Alpine 1789]

Too bad you can't go the other direction - voltmeter hardwired and plug-in ammeter.

 

[hartmandm]

Too bad you can't go the other direction - voltmeter hardwired and plug-in ammeter.

I could figure that out, but not worth the time.

 

[belmateo]

Having had both, all things being equal, I would rather have an amp meter. However, all things aren't equal and my amp meter was very close to starting a fire due to a loose connection that was only discovered accidentally. I will stick with volt meters from now on, especially now that matching ones are available.

Exactly my concern with push on (spade) Connectors. One should at least wire the alternator directly to the starter or battery. The heat that goes through any non secure connection is prone to expansion and contraction. Over time it starts arching etc.

 

[loose_electron]

Volts are more of a static, after-the-fact measurement, that don't offer clues when the driver eventually notices that the needle has deviated from the norm. Useful to a point, but I prefer to know how much flow there is, positive or negative, in real time. Ideally, I'd have both gauges.

Me personally I would use a voltmeter and be done with it. If you really want to count electrons you can put in a metering system similar to what a cell phone has, but that's a lot of fanciness that's not going to be useful.

 

[Tom H]

Exactly my concern with push on (spade) Connectors. One should at least wire the alternator directly to the starter or battery. The heat that goes through any non secure connection is prone to expansion and contraction. Over time it starts arching etc.

I was there when Jim discovered the loose connection on his ammeter, and IIRC it was the nut holding the spade blade to the ammeter that was loose.

As for wiring the Alternator directly to the starter or battery, you need to understand that when you do that the meter will no longer do its job of MEASURING the amps going into the battery from the Alternator. Depending on how you wired the Ammeter it would most likely show the amps going into the electrical system - lights, ignition, blower, etc, - but you would not know if the amps were coming from the battery or the Alt, and it would never read negative, and you would not know if the Alt was working (unless you added a voltmeter, of course)