Installing an Ammeter, Amps / Gauge / Wire Options

[Jaws4God]

I just ordered an Ammeter gauge for my car since I had some problems with my alternator going bad and not knowing because my volt meter read 12 volts...

Does anyone have some tips on how to install it?

Thanks!

This post has been edited by Jaws4God: Jan 23, 2007 - 10:45 PM

[celicadude04]

I believe you connect one wire to the positive output of the alternator and the other to the positive terminal on the battery

[celicadude04]

The stock alternator puts out 70 amps at max iirc, I bought a high output alternator off of ebay which "supposably" has 160 amps capability. As for wire size I'm not sure what size you should use

[Jaws4God]

well I installed the gauge on the output of the alltinator.. it reads about 30 amps when engine running and everything off..
then about 60 when lights and stuff are on..

but the 8ga wire is getting pretty hot plus I really want to read the overall charge and discharge of the battery..

I wish I could install it right at the positive terminal on the battery but the gauge says you can't install it between the battery and starter because it will draw too much amps...

anyone know where to splice in the gauge so that I can get an overall charge / discharge of my car?

Thanks!!

[Mangozac]

Got a link to a pic of the gauge you are using? Is it using a shunt or what? What is the maximum positive and negative readings it can give (+ve readings = battery charging, -ve readings = battery discharging (or being used)). Say you were charging 20A and using -10A, the meter would display +10A.

You see to measure current, you need a sensing element in series with the load. Voltmeters go in parallel with the load. The simplest ammeters use a shunt resistance as a sensing element in series with the load and the meter itself connects across this shunt resistance.

[Jaws4God]

i think the amp gauge helps.

This post has been edited by Jaws4God: Feb 16, 2008 - 10:36 PM

[Mangozac]

OK after some checking out the situation it's like this:

The manual says not to have the starter motor going through the ammeter. Which in retrospect is fine because you don't really need to know what the starter motor is drawing (because it's only on when you crank the engine). So you will just be measuring everything else. I'd be surprised if your alternator will put in more than 60A - but it would be good if someone can confirm this.

Even without including the started motor it will display the way you want it to. And tell you if the alternator is bad.

Your ammeter has an internal shunt resistor. This means that all of the current has to flow through the meter. I don't really like that idea because it means running a fat cable from the battery to the gauge and then back again

You'd be better off with a gauge that uses an external shunt. That way the shunt goes in series with the battery and you simply run some little tiny wires between the shunt and the gauge.


On a side note a friend of mine is trying to talk me into making a little digital gauge that uses a full colour LCD like display. It would be able to show stuff like current but the coolest idea we came up with for a feature was including an accelerometer so that it could display the G forces that you are pulling in both fwd/back and sideways directions. Sure, it wouldn't be many Gs, but it would be cool/fun to see! But it would require a good chunk of time to do, of which I'm very short on these days...

This post has been edited by Mangozac: Dec 13, 2007 - 9:34 PM

[Jaws4God]

nah, I like you idea but I already have the gauge in and mounted...

the instructions say the best place to install the gauges is the wire after the battery and just after the starter.. i see the bundle and where it breaks off to the starter, but I have a feeling there isn't 1 wire there, so I wanted to see if anyone knew which one came from the altinator and also powers other devices so i can get an overall reading.

Thanks!

[Mangozac]

nah, I like you idea but I already have the gauge in and mounted...

the instructions say the best place to install the gauges is the wire after the battery and just after the starter.. i see the bundle and where it breaks off to the starter, but I have a feeling there isn't 1 wire there, so I wanted to see if anyone knew which one came from the altinator and also powers other devices so i can get an overall reading.

Thanks!

I said wait until I read the other manual before you reply!

Fair enough if it's all mounted. There should be two wires that do to the battery + terminal. The fat one is the starter motor. The other one is everything else. You need to be in series with the other one.

[Jaws4God]

nah, I like you idea but I already have the gauge in and mounted...

the instructions say the best place to install the gauges is the wire after the battery and just after the starter.. i see the bundle and where it breaks off to the starter, but I have a feeling there isn't 1 wire there, so I wanted to see if anyone knew which one came from the altinator and also powers other devices so i can get an overall reading.

Thanks!

I said wait until I read the other manual before you reply!

Fair enough if it's all mounted. There should be two wires that do to the battery + terminal. The fat one is the starter motor. The other one is everything else. You need to be in series with the other one.

i'll see if I can check today, that would be so awesome is there is only 2 main wires coming off of the battery.

this is the bundle i'm talking about.. looks a little too big for only 2 wires



This post has been edited by Jaws4God: Feb 16, 2008 - 10:35 PM

[Mangozac]

i'll see if I can check today, that would be so awesome is there is only 2 main wires coming off of the battery.

this is the bundle i'm talking about.. looks a little too big for only 2 wires

Pull the rubber cover bit off the battery terminal and see how many wires are actually bolted onto the terminal clamp. My bet is that your 2 wires will be there.

[BloodyStupidDave...]

For anyone else thinking about doing this, what you want is either a meter with an external shunt resistor as Mangozac said, or (better) a DC clamp meter.

The later uses some clever electronics to read the magnetic field around a conductor and calculate the amperage required to generate such a field. The sensor is clamped to the insulation of the conductor (that is, the sensor is in very close proximity to the conductor, not actually making an electrical connection).

Because there isn't a physical connection, it is possible to read very large amperages without the need for running everything through the actual meter and so you can choose which wire you want to measure.

Some ECUs have the ability to monitor the amps and volts, AFAIK this is not true of any of the ECUs for the Celica.

[Jaws4God]

i'll see if I can check today, that would be so awesome is there is only 2 main wires coming off of the battery.

this is the bundle i'm talking about.. looks a little too big for only 2 wires

Pull the rubber cover bit off the battery terminal and see how many wires are actually bolted onto the terminal clamp. My bet is that your 2 wires will be there.

BINGO! I tore that apart and found 2 main wires, one goes straight to the starter and the other runs down and heads towards the fuse box. So I left the starter wire on the battery, then ran my ammeter between the "accessory wire" and the battery

so now it reads about 10 amps when running.. when car is off and turn my headlights on, it reads -30..

so it reads the overall charge / discharge of the battery and should not push too many amps through my gauge

YAY thank you all!!

This post has been edited by Jaws4God: Dec 15, 2007 - 12:03 AM

[Mangozac]

Yay!

Good job Dan! We'll make an auto electrician out of you yet!