Shunt

[GerryS]

Does anyone make a ammeter shunt that can can directly connect to my wing nut battery post that would have a wing it type connector on the opposite side, allowing an installation with just removing the battery cable and inserting the shunt between the two with no jumper?

I'd love a simple clean install and not have to for an external shunt and a jumper between it and the battery where space is already very tight....

I've searched the interwebs already and come up with nothing....probably the search terms I'm using. I can't see this as being an odd request....

[Dale M.]

Umm... Shunt is going to have to be calibrated to work with meter you are using.... Its usually just a resistance of some low value and meter is only reading small variation of current flow that is going directly through meter bypassing shunt....

You might be able to make your own if you can find proper "resisitive" material and know value mater requires...

Dale

[MtnDon]

I have a couple of the typical 500 amp shunts with stud and nut terminals. I cut a short piece of copper bar stock (3/16 x 1_ and mounted the copper bar on one lug. Drilled to fit the battery stud. The battery cable mounts to the second stud on the shunt.

As for calibrating maybe his is like mine; it's for connecting to a system that simply requires a 'standard' 50 mv 500 amp shunt

[Corwin C]

I may be incorrect, but I thought that a shunt generally is only good for short duration and when the current is too high to be measured directly. If used continuously they can become heated by the current then their readings will drift. Is your current too high to measure directly? Perhaps a hall effect sensor would be another option.

[MtnDon]

Yes, a shunt is used when current is too high for direct and easy measurement. In the alternative energy world shunts are used often with a variety of instrumentation setups. The shunts are in full time use. A popular instrument is the Trimetric meter from Bogart Engineering. We have an Outback Flexnet DC. It employs three 500 amp shunts; 1 in the charge controller (PV panels) output to the batteries; all output from the PV panels go through that shunt. A second is in the DC output to the inverter. I have a third for a future possible wind generator. The flexnet meters all the current going in and out of the batteries. It is pretty much a fancy "fuel level gauge" for the batteries. Lots of statistical info available. Runs 24/7.

The shunts we use are Mil-Spec. Drift if any is very minimal.

[Breytie]

Shunts are the simplest, most rugged and cheapest way to measure high AC and/or DC currents. I have worked with units rated at 100A continious. At high ratings they are of a 4-terminal design: Two massive main connectors on the outer ends and 2 measurement terminals to the inside of them. That way the stray resistance of the main terminals do not affect the accuracy of the measurement.
Shunts are normally rated at a few mV output at their rated current.
One important thing to remember: the measurement circuit must me isolated ftom the rest of the measured circuit to prevent errors or explosions.
A whole selection up to 1000A can be seen on Farnell's web sitehttp://export.farnell.com/current-shunts

[Corwin C]

OK ... I think I understand. Gerry will be measuring the total amps which pass the shunt rather than the instantaneous current. And everything is rated for continuous use. Thanks for the lesson.

[GerryS]

I just am looking for a meter and shunt that I can simply install the shunt as an extension of the cable directly to the battery.....neat, and small. The shunts I've seen are all like this one...big and require external cables to jump between the shunt and the battery...

http://www.reuk.co.uk/What-is-a-Shunt.htm

I'm curious if there are smallish ones that are on the end of the battery cable...making is compact clean install without the use of the jumper.

[Breytie]

Sorry Gerry
I didn't clearly say what I meant .
Many shunts have connecting lugs (holes) and thus can go straight between the cable and battery lug - Just make sure of the following:
- What your meter/display unit requires from the shunt (mV per A)
- What your max current draw will be - then if possible double it as a fudge factor
- Make a drawing of the battery lug and make sure to get a shunt compatible with the size and shape.
Browse through some on-line catalogs and datasheets, and if still unsure, speak to your local electronics or electrical suppliers to get the right item for your needs

When mounting up the lot try to put as little strain as possible on the shunt, distortion will change the accuracy.
Air flow around the shunt is important to keep it as cool as possible.

Good luck!
Andre

[bdosborn]

http://www.allelectronics.com/index.php?page=seek&id[m]=pattern&id[q]=shunt&x=0&y=0

You'll have to copy and paste as the [] in the URL screw up the forum URL function.

Bruce