How to wire a 12v 0-50amp digital amp meter to 12v RV house battery.

Thread Starter

santiam

Joined Feb 14, 2019
7
You wire it in series with the output of the battery.
Do you have info on the ammeter you want to use?
Answer:
I haven’t picked one out specifically yet. I was considering a12v 3-50v, 0-50amp with a matching shunt. I have 2-6 v Trojan T-105’wired in series for 12v’s, on RV house batteries, (225 AH).I have a in house generator, and a 110v-12v power supply/charger and the RV alternator that are connected to house batteries.

I wired in a 9volt powered digital 5 digit v meter off the 12v house battery. It is working good. It shows v with the 12v battery at rest and when turning on gen, shore power and rv alternator. It has a lighted on/off switch from 9volt battery.

Wanted to to add a amp meter to measure the overall amperage from RV 12v excesseries like refer, lights and fans etc. against the 12v house battery.

Next the net amperage when gen, shore power or generator are on.

I have read online about wiring it in series with preferably ground side. But specifically how do you wire in the shunt and then the amp meter. I understand you wire the shunt in Series with ground wire off battery, which is very large diameter wire. Not sure how to accomplish that.

Then how do you wire in amp meter in? 2wires to shunt and where do others wires go from amp meter?
 

Reloadron

Joined Jan 15, 2015
5,605
Below is a typical example of a 50 Amp shunt.
50 Amp Shunt.png

Notice the large copper lugs in the current path. This shunt is a 50 Amp / 50 mV shunt so the small voltage output terminals output a voltage proportional to the current.

Something you may want to consider is a battery in your situation may have bi-directional current flow. When a load is on the battery current flows in one direction and when the battery charges the current flows in the other direction. Simply put, the mV out of the shunt will toggle based on the direction of current flow. Actually the shunt will measure -50 to 50 Amps with a mV out of -50 to 50 mV. 1.0 mV / Amp. In this case I would want a mV meter which has a bi-polar input.

Something else to watch out for is current shunts including meters are pouring in from China. Should you choose one of these and wish to power the meter off the battery you are measuring make sure the meter voltage and the input voltage to be measured can share the same common (- negative).

Ron
 

crutschow

Joined Mar 14, 2008
25,255
The shunt goes in series with the battery with generates a small voltage proportional to the current through it.
This voltage is then carried by two small wires from the shunt to the meter, which displays a current from this voltage.

To connect the shunt you could buy an extra battery cable something like this.
 

Thread Starter

santiam

Joined Feb 14, 2019
7
Answer:
I haven’t picked one out specifically yet. I was considering a12v 3-50v, 0-50amp with a matching shunt. I have 2-6 v Trojan T-105’wired in series for 12v’s, on RV house batteries, (225 AH).I have a in house generator, and a 110v-12v power supply/charger and the RV alternator that are connected to house batteries.

I wired in a 9volt powered digital 5 digit v meter off the 12v house battery. It is working good. It shows v with the 12v battery at rest and when turning on gen, shore power and rv alternator. It has a lighted on/off switch from 9volt battery.

Wanted to to add a amp meter to measure the overall amperage from RV 12v excesseries like refer, lights and fans etc. against the 12v house battery.

Next the net amperage when gen, shore power or generator are on.

I have read online about wiring it in series with preferably ground side. But specifically how do you wire in the shunt and then the amp meter. I understand you wire the shunt in Series with ground wire off battery, which is very large diameter wire. Not sure how to accomplish that.

Then how do you wire in amp meter in? 2wires to shunt and where do others wires go from amp meter?
Below is a typical example of a 50 Amp shunt.
View attachment 170203

Notice the large copper lugs in the current path. This shunt is a 50 Amp / 50 mV shunt so the small voltage output terminals output a voltage proportional to the current.

Something you may want to consider is a battery in your situation may have bi-directional current flow. When a load is on the battery current flows in one direction and when the battery charges the current flows in the other direction. Simply put, the mV out of the shunt will toggle based on the direction of current flow. Actually the shunt will measure -50 to 50 Amps with a mV out of -50 to 50 mV. 1.0 mV / Amp. In this case I would want a mV meter which has a bi-polar input.

Something else to watch out for is current shunts including meters are pouring in from China. Should you choose one of these and wish to power the meter off the battery you are measuring make sure the meter voltage and the input voltage to be measured can share the same common (- negative).

Ron
 

Thread Starter

santiam

Joined Feb 14, 2019
7
Thank you very much,

Most of the 0-50 amp digital amp meters have 4 wires. Two go to the stunt. You have explained how to do that. From below post don’t use ground wire for stunt, use hot wire.

Where do the other 2wires on the amp meter go to?

I found 0-50 amp meter with 3-50v on eBay but not sure how to send the picture and info to you.
 

Thread Starter

santiam

Joined Feb 14, 2019
7
Answer:
I haven’t picked one out specifically yet. I was considering a12v 3-50v, 0-50amp with a matching shunt. I have 2-6 v Trojan T-105’wired in series for 12v’s, on RV house batteries, (225 AH).I have a in house generator, and a 110v-12v power supply/charger and the RV alternator that are connected to house batteries.

I wired in a 9volt powered digital 5 digit v meter off the 12v house battery. It is working good. It shows v with the 12v battery at rest and when turning on gen, shore power and rv alternator. It has a lighted on/off switch from 9volt battery.

Wanted to to add a amp meter to measure the overall amperage from RV 12v excesseries like refer, lights and fans etc. against the 12v house battery.

Next the net amperage when gen, shore power or generator are on.

I have read online about wiring it in series with preferably ground side. But specifically how do you wire in the shunt and then the amp meter. I understand you wire the shunt in Series with ground wire off battery, which is very large diameter wire. Not sure how to accomplish that.

Then how do you wire in amp meter in? 2wires to shunt and where do others wires go from amp meter?
The shunt goes in series with the battery with generates a small voltage proportional to the current through it.
This voltage is then carried by two small wires from the shunt to the meter, which displays a current from this voltage.

To connect the shunt you could buy an extra battery cable something like this.
Thank you
Great Help.
 

Reloadron

Joined Jan 15, 2015
5,605
So this will be strictly one way unidirectional current flow? You will only look at discharge and not charge? If you want both I suggest you look at Yaakov's post and link above.

That being the case then the unit you linked to should work out fine wired as Crutschow covered, power and shunt. They normally come with a small diagram of the wiring.

Ron
 
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