On Sunday, April 23, 2017 at 7:47:35 PM UTC-4, mike wrote:
On 4/21/2017 5:25 PM, wrote:
Not full. A sampling device connected to an auto amp gauge. For example, the gauge may read 10 amps on a full sweep. Is this too much for outside the dash ? How is this done if it is done on a Kenworth ?

The alt is 200 amps above 65 mph.

There are TSD factors using stereo 40 amp fuse, lights @ 30 amps, vehicle OP amps @ 75 ... where quantifying the load vs miles to go vs a positive battery charge is useful. Better than. 'geee whiz the lights are yellowing' ... as too late n that is 3 hours with no aux load to reach white light again?

Not clear what you're trying to accomplish.
You will be adding at least two additional failure points in the system.

Why is the alternator current important?
If the battery is charging, you're good to go.

The thing you care about is the battery voltage.
If the alternator output is sufficient, you will be able to see
it on a voltmeter.

That can be done trivially...
http://www.ebay.com/itm/New-LCD-Ciga...1%26rkt%3D1%26

In the old days, cars had ammeters. The problem is that it was difficult to discern if the needle was slightly left or right of center. Today cars have voltmeters which tells more in my opinion.

In a 12V system, anything more than 12.6 indicates a positive charge condition. I had a condition recently where my alternator's internal regulator failed and it was pumping 17V into the car. The ammeter would not have shown this quite as clearly.