Ammeter/ Volt meter adjustment

[Gjac]

I installed a cheap meter to read volts and amps sometime ago along with a shunt. There are two pots on the meter one for volts and one for amps. The volts I set with my volt meter but the amps I can figure the best way to adjust it. I don't have another ammeter to check it with. It only reads 5 amps when my 2 6v GC batteries are at 50% SOC with a 180 amp alternator so I am thinking either my meter is off or something is off with my charging wiring. Has anyone adjusted these meters using the 12v lights or another simple way without another ammeter?

[CA_Traveler]

The shunt is intended to measure the battery amps and NOT the charger amps. The amps supplied by the charger FIRST feed any house loads and then any remaining charger amps go to the battery.

[BFL13]

By "outer end" I mean the end away from the battery that all the neg wires go to. By "inner end" I mean the end that is attached to the neg battery post.

I would get the voltage right and let the amps fall where they may. It might be the amps adjustment amount varies with the range of amps so maybe adjust the amps when amps are closer to 100 (midway for the 200a shunt) or for whatever would be the average amount of amps you usually would be running.

[Gjac]

My adjustment is not going any better. My B&D reads 6.4 a but the most that I can get the amps to read by turning the pot clockwise is 3.8 a. The problem the volts go to 64 volts. So I readjusted the volt pot back to 15.4 v. but could not get move then 3.8 a or less than .1 amps. Maybe Richard was right or I am missing something. I am not sure by what you mean by the "outer edge of the shunt". My shunt has a large cable going to the frame and grounded by a bolt the other cable goes to the neg post of the second 6V GC battery wired in series.

[BFL13]

The inverter neg would go to the outer end too but only if you are using the ammeter to measure draws not charging inputs, with the one way meter.

I just tried to calibrate my ammeter part and the same little screwdriver that turned the voltage pot easily would not turn the ammeter pot so I pushed harder and the pot screw head came off!!! Drat, very flimsy. So now there is nothing to grab onto to turn it and it is stuck. Also I must have done something because it was reading 3 amps (with 12 amps worth of lights on) and after I broke it, it read 234 amps. Phooey. So now I have a $12 voltmeter and don't need the shunt. I think the shunt will make a good buss bar for another job though.

Hope your meter project goes better than mine did! 🙂

[Gjac]

I am charging my house batteries now at 15.4 v and 7.3 a according to my B&D 40 amp charger. The meter in question reads 15.2 v and 1.3 amps. My HF meter reads 15.3 v. Once it stabilizes I will try to adjust the pot to read the same as the B&D charger reading.

[Gjac]

MrWizard wrote:
Are you trying to read chassis/engine batteries or house batteries
Any measuring device (the shunt)
Must go in between ALL CURRENT FLOW in and out of the batteries
Is the negative from ALL your charging systems connected to the chassis and not to the battery negative

I am trying to measure the house batteries. My shunt is connected between the frame and the neg post of my house batteries.

[MrWizard]

Are you trying to read chassis/engine batteries or house batteries
Any measuring device (the shunt)
Must go in between ALL CURRENT FLOW in and out of the batteries
Is the negative from ALL your charging systems connected to the chassis and not to the battery negative

[Gjac]

BFL13 wrote:
You probably know, but when you use the portable charger, its neg clamp goes on the outer end of the shunt same as where your chassis ground wire is, not on the battery post end of the shunt. Or you could just put the neg clamp to the chassis (frame) somewhere and the neg path will go to the outer end.

I did not know this. I charge my batteries inside of the MH off my pos and neg posts of the inverter under my dinette seat. I just plugged the MH into shore power the resting volts where 12.58v and the amps when from -.3 to 0. So with my old Magnatech converter it is charging at 13.06 volts and .3 amps. I will try your setup to the frame with the B&D charger.

[BFL13]

You probably know, but when you use the portable charger, its neg clamp goes on the outer end of the shunt same as where your chassis ground wire is, not on the battery post end of the shunt. Or you could just put the neg clamp to the chassis (frame) somewhere and the neg path will go to the outer end.

[Gjac]

CA Traveler wrote:
Is the shunt wired to the battery post so that it reads all of the battery amps?

The shunt is wired from chassis ground to the neg battery terminal as my diagram shows. Is that what you are asking?

[Gjac]

BFL13 wrote:
I figured out a way to get it to read amps both ways (if I can get it to read amps at all) using a small throw-type A-B switch I have in the spares box. A set of wires (opposite ways) from the shunt to the switch to A and B, then single set to the display? That way you don't have to swap wires on the shunt to see amps the other way, just throw the switch. (if it works)

I thought I had mine working when I had it jury rigged a few inches from the shunt. It was showing 33 amps, 14 amps, and 2 amps for different loads I tried.

Now at 15 ft away from the shunt using Trimetric cable wires it won't show amps at all. (you have to pick the right black wire of the two) Might need fatter wire than Trimetric uses?

Mine will read amps. With nothing on it reads -.4 amps. I assume that is the Co2 detector. Each light that I turn on adds about -.4 amps. I just question the amps from the alternator, I thought I would get more than 5 amps. I will recharge with my 40 amp B&D charger and see if it compares closely to it. My batteries have been disconnected with no charge since Oct 1st but are probably still better than 90% so they won't take many amps.

[BFL13]

I figured out a way to get it to read amps both ways (if I can get it to read amps at all) using a small throw-type A-B switch I have in the spares box. A set of wires (opposite ways) from the shunt to the switch to A and B, then single set to the display? That way you don't have to swap wires on the shunt to see amps the other way, just throw the switch. (if it works)

I thought I had mine working when I had it jury rigged a few inches from the shunt. It was showing 33 amps, 14 amps, and 2 amps for different loads I tried.

Now at 15 ft away from the shunt using Trimetric cable wires it won't show amps at all. (you have to pick the right black wire of the two) Might need fatter wire than Trimetric uses?

[RJsfishin]

Gjac wrote:
My meter reads from 0-200 volts and 0-200 amps. The shunt is 200 amps and 75 mv.

That meter is worthless for anything under 10 amps.
You should match the ammeter's total capacity to near the max amps you want to read.
That same 200 amp meter was worthless for my 45 amp converter. (on the junk shelf now)
The same meter in the 50 amp model works perfect, even down to less than 1 amp on my solar. I learned the hard way, so are you.

[Gjac]

doughere wrote:
Your shunt is a resistor. Your ammeter is actually a voltmeter reading the drop across your shunt. If you know the shunt's value (usually expressed as Amp to millivolt drop) you can read the voltage across the shunt and calculate the Amperage. My shunt is 50 Amp to 50 mV; so if the volt reading across the shunt is 35 mV, my meter should read 35 Amps. The most common shunts are designed for 50 or 100 mV at max current reading.

Doug

Doug if I understand your post if I take a voltage reading between the two large nuts across the shunt(as shown in BFL's post)and trust my voltmeter I could adjust the amp pot to match that reading. Is that what you are saying?

[Gjac]

BFL13 wrote:
Must be the same one I got:

http://www.ebay.ca/itm/DC-0-300V-200A-Shunt-Voltage-Current-Panel-Meter-Digital-LED-Voltmeter-Ammete...

Note the display resolution is 1 amp. First you have to get the festering thing to show any amps at all! Landyacht warned about that. I get sporadic readings of amps, mostly says zero. Not sure what the matter is --connections ok.

Do I need to use fatter wire from display to shunt for the amps to read anything? The Tri was with a 500a shunt- this is a 200. I am using the same wire the Trimetric has at that distance (15 ft?) from the shunt. I got the voltage calibrated easily enough.

That looks like the same one.