Current measurment..

aussie_paul · Guru

Current measurment..

Jaahn · Guru

Hi Paul,

I am no good at drawing a diagram on the computer so I can only say this. cry

Imagine the battery is that "tested device" on the diagram you have. Then take off the earth lead from the battery -ve and get another short battery lead as well. Then connect the original earth lead to one end of the current shunt. Then connect the short lead to the battery -ve terminal and the other end of it to the other end of the current shunt.

Then you have installed the current shunt in series with the earth return of the battery.All the current will go through the shunt so you can measure it with your meter connections. Then connect the other wires as shown + and - and ready to go. biggrin

Jaahn

aussie_paul · Guru

Jaahn wrote:
Hi Paul,
I am no good at drawing a diagram on the computer so I can only say this.
Imagine the battery is that "tested device" on the diagram you have. Then take off the earth lead from the battery -ve and get another short battery lead as well. Then connect the original earth lead to one end of the current shunt. Then connect the short lead to the battery -ve terminal and the other end of it to the other end of the current shunt.
Then you have installed the current shunt in series with the earth return of the battery.All the current will go through the shunt so you can measure it with your meter connections. Then connect the other wires as shown + and - and ready to go.
Jaahn

Thanks, Jaahn, that is what I figured BUT placing it in the - negative line surprised me. biggrin

Aussie Paul. smile

dogbox · Guru

can't follow wouldn't the battery be the two leads red + black - an the tested load the item drawing power (fan)

if i'm reading it wrong I would have probably let the smoke out

-- Edited by dogbox on Thursday 3rd of September 2015 05:38:58 PM

Jaahn · Guru

aussie_paul wrote:
Jaahn wrote:
Hi Paul,
I am no good at drawing a diagram on the computer so I can only say this.
Imagine the battery is that "tested device" on the diagram you have. Then take off the earth lead from the battery -ve and get another short battery lead as well. Then connect the original earth lead to one end of the current shunt. Then connect the short lead to the battery -ve terminal and the other end of it to the other end of the current shunt.
Then you have installed the current shunt in series with the earth return of the battery.All the current will go through the shunt so you can measure it with your meter connections. Then connect the other wires as shown + and - and ready to go.
Jaahn
Thanks, Jaahn, that is what I figured BUT placing it in the - negative line surprised me.
Aussie Paul.

Hi Paul,

Actually it does not matter whether you put it in the negative line or the positive line, the current has to go out and comes back just the same amount. The only difference is the wires for the meter must be correctly fitted for it to work OK.

Sometimes the negative is easier as it has less connections. the fuses and switches etc are usually on the positive line so it may be a bit messier to put it there. hmm

Dogbox,

The diagram is for a different layout so you have to think it as a different layout and i suggested to think of it like I said to make it easy to visualise from the given diagram.

Jaahn

Leather Tech · Veteran Member

Hi Paul
Can you please keep us all updated as to how good this unit is at measuring amp usage. I would be very interested in buying one myself if it works .
Peter

aussie_paul · Guru

Leather Techs wrote:
Hi Paul
Can you please keep us all updated as to how good this unit is at measuring amp usage. I would be very interested in buying one myself if it works .
Peter

I certainly will. Tomorrow is test day. Success or smoke. biggrin

Aussie Paul. smile

The Doo crew · Senior Member

Will be smoke if you do it incorrectly. Cheapy from e-bay, not too bad for what they are.

Tested item is your "house" wiring, lights, fans & such. Battery is power supply & if you try to use it on the positive side of your wiring smoke will result.

Simple fitment of the "shunt on the negative side of your battery with a short lead & the wire you remove from the battery then bolts to the other end of the shunt.

I use three of these to keep track of my solar panel input, reasonably accurate & fun to play with.

-- Edited by The Doo crew on Friday 4th of September 2015 02:20:17 PM

aussie_paul · Guru

The Doo crew wrote:
Will be smoke if you do it incorrectly. Cheapy from e-bay, not too bad for what they are.
Tested item is your "house" wiring, lights, fans & such. Battery is power supply & if you try to use it on the positive side of your wiring smoke will result.
Simple fitment of the "shunt on the negative side of your battery with a short lead & the wire you remove from the battery then bolts to the other end of the shunt.
I use three of these to keep track of my solar panel input, reasonably accurate & fun to play with.

-- Edited by The Doo crew on Friday 4th of September 2015 02:20:17 PM

Thanks Mike, about to go out and give it a try.

Aussie Paul. smile

aussie_paul · Guru

Ok no smoke, so that's good. biggrin I want to be able to mount it near the solar controller so I can view it easily. I will have to run the yellow wire back to the shunt. Pretty easily done now that I know my system almost back to front now!!!

The temporary test installation showed more current the more things I turned on. Should it show amps going into the batteries?

Aussie Paul. smile

-- Edited by aussie_paul on Friday 4th of September 2015 10:26:28 PM

-- Edited by aussie_paul on Friday 4th of September 2015 10:30:05 PM

PeterD · Guru

Paul, yes it should show the charge current. I see that the discharge current is shown as a + ve reading. It will probably have a " - " sign in front of the current reading (ie negative discharge.)

The Doo crew · Senior Member

My three set up to monitor the input from the 3 solar panels so they only show charge, at 6 bucks each + the shunt its a good way to see if I have something stopping my solar working at its best like leaves or bird s**t on the panels, saves climbing up to check.

Woody n Sue · Guru

The doo crew that's a cool ideas have one on my hydrogen generator hadn't thought of putting one on my solar inputs my just do that when I fit my new panels

The Doo crew · Senior Member

Woody, the idea came after running low on power after a couple of days parked up, couldn't understand why we were not "making enough" during the day.

Turned out it was a huge bat s**t on two panels that dropped our charge to just 4 amps during the day. We run two compressor fridges & the usual USB chargers but no telly so normally at full charge well before lunch. Can normally even run the split air-con for an afternoon siesta for a few hours without an issue.

I have found even a couple of good sized leaves can slow things up, getting it out & climbing the ladder just to check is a pain, can make a judgement call if I can see by the meters only one is down on charge.

Even have one in the dash to keep an eye on the alternator output, Coaster 24v, 24v fridge & inverter for 240v & 24v solar with the rest of the house all running on 12v so it pays to keep an eye on things before they become a problem that causes grief.

2 way VSR keeps everything topped up when driving or parked up & have even relied on solar to keep us on the move when an alternator failed out bush trip, got us to a major town where we could get a replacement.

Have a 4 stroke 0.8kva genny that runs on LPG gas as a back up but have never had to use it in anger so far, haven't looked into the hydrogen generators yet, maybe soon.

madaboutled · Guru

I have my panels wired separately to individual switches so I can test & compare how each one is going, which has proved handy to identify fault issues with each panel.

mjt57 · Senior Member

PeterD wrote:
Paul, yes it should show the charge current. I see that the discharge current is shown as a + ve reading. It will probably have a " - " sign in front of the current reading (ie negative discharge.)

With that shown wiring diagram, how would it show charging current? The wire (-ve) from the charging source would need to be spliced into the shunt between the "tested device" or load and the shunt itself.

The specs don't indicate if it shows negative values. Just says "0-100a".

Still, if it's only $7 or so, getting a few of them won't break the bank.

Now, question from a caravan wannabe. How do you run new wiring, say, for this particular project, through the van? Can you access the space behind the walls? If it has to be external I'd say that my wife would be most upset if I ran conduit or whatever, through the van where it's visible!

aussie_paul · Guru

Ok, interested parties. I have had a chance, while Eril was visiting flower gardens, to wire my amp meter. biggrin It took me a while to work out a few things though. It does not show positive amps only discharge. When the the solar input is higher than the discharge the meter says zero. After the sun goes down this evening I will see the current drawn by our different appliances. I was able to simulate this by disconnecting the solar input for testing purposes.

All I have to do now is tidy up the wiring and mount meter. I can use the 240 soldering iron when the genset is running for coffee. biggrin

I am not sure how accurate it is at the moment until I can check with a quality amp meter.

Aussie Paul. smile

-- Edited by aussie_paul on Tuesday 15th of September 2015 05:44:01 PM

Ondabeach · Senior Member

We really need to know how the meter is situated in relation to the batt and the charging input Paul, but since that meter can't show which direction the current is flowing I'd recommend having two of them wired up. One set up with the battery as the power supply and the van as the tested device, and one wired with the solar as the power supply and the battery as the tested device.

aussie_paul · Guru

Ondabeach wrote:
We really need to know how the meter is situated in relation to the batt and the charging input Paul, but since that meter can't show which direction the current is flowing I'd recommend having two of them wired up. One set up with the battery as the power supply and the van as the tested device, and one wired with the solar as the power supply and the battery as the tested device.

The Morning Star Prostar tells me the solar input to the house batteries, and this meter tells me what I am drawing above solar input. Have I explained that well enough?

Aussie Paul. smile

Ondabeach · Senior Member

It sounds like this to me Paul.

Solar panel - prostar - battery - chinese meter - van.

If that's how it's hooked up then the prostar is telling you the total current it's supplying the batts and house combined and the chinese meter is telling you how much current is going to the van from the solar and batts combined.

You would then need to subtract one reading from the other to know whether you're batteries are charging or discharging.

meggsy · Veteran Member

This one does both charge and discharge http://www.ebay.com.au/itm/DC-90V-30A-Volt-Amp-Battery-Capacity-AH-Power-Combo-Meter-Charge-Discharge-Timer-/181114198565?hash=item2a2b3f5a25