[Jeffd]

Hi Folks, I bought a "2in1 Car Motorcycle LED Digital Voltmeter Ammeter Voltage Meter DC 12V-24V" from Ebay for £8 and it arrived today small and round with 3 pins on back marked +, - and the center one has like a 'u'
How on earth do you wire it in to monitor the ampage? I guess the + and - go direct to the battery and it gives voltage but where to wire the other one to see what ampage is being used?
Anyone got any clues?

 

[d1giPhux]

@Jeffd

Check this video out:

Seems pretty simple. 2 go to positive, ground goes to black.

One of the positive seems like it measures the voltage and one is power for the unit itself?

 

[Jeffd]

Ummmmm...... yes, fine for just measuring voltage BUT which voltage does it read? I need to know how to get the voltage on the under hood battery and would like to check/measure the varying ampage during a run
It would be easy if we had an alternator but with the feed from the main battery just trickling the 12v under hood I think I might give up!!!?
The ECU will probably throw a wobbler???

 

[Spdbump]

Ummmmm...... yes, fine for just measuring voltage BUT which voltage does it read? I need to know how to get the voltage on the under hood battery and would like to check/measure the varying ampage during a run
It would be easy if we had an alternator but with the feed from the main battery just trickling the 12v under hood I think I might give up!!!?
The ECU will probably throw a wobbler???

I am not sure if this helps but through the OBD II port on my Scan Gauge II I can monitor the battery and do. It Ranges from 12.X to 14.X when running to 11.X when in accessory 1 engine off.

 

[Jeffd]

Thanks Boss My OBD reader causes 'problems' after reading ( as posted before ) so I will give that a miss.
These little Z boogars are too sensitive to any electrical shenanigans

 

[Spdbump]

Thanks Boss My OBD reader causes 'problems' after reading ( as posted before ) so I will give that a miss.
These little Z boogars are too sensitive to any electrical shenanigans

I have had 0 issues with my Scan Gauge II which has been continuously hooked up since 2013. It has caused no issues and has detected some issues. A Crank Position Sensor, and reads all other relevant readings.

 

[Jeffd]

That sounds a nice piece of kit.
Mine is a cheapy and only gives codes.
I think I'll just settle on monitoring the voltage.
Bought a space saver but it is a full 2 inches larger than the standard! That is another story for another post sometime.
Off out now so have a good evening and catch you later ATB.

 

[Hakugin]

A proper ammeter should come with a shunt resistor that is used to read the current between your power source and a single device. IE: battery and headlight or battery and audio amp. While it sound be possible to measure the current from the battery to everything else, it would require a very hefty shunt resistor. It would need to be able to handle the full cranking amps of the engine using the starter. Usually these are 1 ohm, or at least close enough for a meter to perform the calculations for converting voltage and resistance into current.

Tl;dr ... Did it come with a high current shunt resistor? If not then it probably won't work as expected.

 

[Jeffd]

That is the problem! No instructions. Not even in flipping Chinese.
I've given up trying to read the ampage, thanks for input.

 

[Eddie70]

I bought a cell phone charger on Amazon that plugs in the 12V outlet. It has a digital readout of the 12v battery all the time when the key is on. Like mentioned above mine ranges from 11 volts with the car off up to 14.1 or so with the car running.

 

[Jeffd]

Cheers Eddie, I've seen those.
Back in the 60s' many cars had an ammeter, this is what I wanted to replicate but our charging system seems not to allow it

 

[Spdbump]

But didn't they also have generators rather than alternators? If that is true than an Ammeter may not be a useful measurement. We have a Generator but it is also used as a motor so not sure if an Ammeter reading would be useful or if there is any point in this car we can read the Amps from.

Cheers Eddie, I've seen those.
Back in the 60s' many cars had an ammeter, this is what I wanted to replicate but our charging system seems not to allow it

 

[Jeffd]

Spot on mate.
You could check ampage output from the alternator easily. I remember that sitting at a standstill I needed 1200 rpm to get positive ampage to keep the battery from draining, I was looking for a way to check when the CR-Z is actually 'gaining' charge ìn the 12v as I have suffered a flat battery after just sitting with the radio on for 30 mins!!
I'd be happy to sit with the engine ticking over but at what revs???

 

[Spdbump]

On the Scan Gauge II if I see over 12 volts then I know the battery is charging ( usually when driving around I see 13.X volts but have seen 12.X) When sitting in accessory 1 position I see anywhere from 12.5 to 11.7 depending on how long I was sitting in Accessory 1 listening to radio. If I ever see it drop to less than 11.4 I will start engine and let the car charge the under hood battery. I would not worry about the RPM the car knows what to do.

I just don't worry about it. I have the gauge and I check it sometimes. The CR-Z is smarter than I am and I presume with The Scan Gauge and the habits I have developed I will not get stuck again and if I do I have a LI-ION jump starter in the car which I charge quarterly.

Spot on mate.
You could check amperage output from the alternator easily. I remember that sitting at a standstill I needed 1200 rpm to get positive ampage to keep the battery from draining, I was looking for a way to check when the CR-Z is actually 'gaining' charge ìn the 12v as I have suffered a flat battery after just sitting with the radio on for 30 mins!!
I'd be happy to sit with the engine ticking over but at what revs???

 

[Jeffd]

I too carry a mini jump starter.
It does not take much to power up the ECU and off she goes.
OK mate. Thanks for info. I'll live with the Z

 

[Spdbump]

As it needs so little to start it off we can have a much more dead under hood battery than other cars and still be able to start. Which when you think about it, is really quite amazing!

I too carry a mini jump starter.
It does not take much to power up the ECU and off she goes.
OK mate. Thanks for info. I'll live with the Z