Battery shunt resistance?

The resistance of the shunt will be so low it'll be tough to measure without a meter that has kelvin capability.

There isn't much that can go wrong with a typical shunt. I would check the connections to the shunt and make sure they're tight. Some shunts have a thermal coefficient that can foul up readings but that would be a long term effect.

Well it seems like it's the meter. Without the shunt in place it is reading over 10a charging...

You need to know the current rating of the shunt as well as its design voltage to figure its resistance; at that point, it's just an application of ohm's law.

If, for instance, it's a 100A 75mV shunt, then .075V = 100 R, or R = .00075 ohm ( that is 0.75 milliohm). Very few multimeters will measure that; the minimum resistance range on my Fluke 73, for example, has a precision of 0.1 ohm.

Before completely blaming the meter, see what it reads with the input short-circuited. With an open circuit input, it may be picking up enough stray charge to read most anything (particularly if it's a digital meter). Checking the calibration of it would be easier by applying a known test voltage in the 0 to 75 mV range.

It's possible for poor contact at the shunt connections to lead to incorrect readings at times, too.

I doubt if the shunt itself is bad. More likely the Heavy Duty connections need attention.


If the main shunt would open up then the MV meter movement would most likely pulverize with all of the DC CURRENT going thru it...

This is why I like the HALL EFFECT Senor measure as the DC cable you are wanting to measure just simplify passes through the cent of the coil.

These Hall effect Dc current samplers were readily available a few years ago at a good price from a China company called SURE ELECTRONICS but that all changed for some reason... You could buy a complete kit with digital meter for around $35 calibrated for 75A or a 100A.. Unfortunately for me I only bought one back then haha...



The Hall Effect Sensors made by Honeywell were ideal for my apps where you just route the large cable you want to measure thru the device. Nothing to short out and touch ground etc... I need to find some more available sources for these type of sensors in 75A to 100A ratings.

Roy Ken

Well the real problem is I went cheap and got a Chinese meter. I think I need to get a tri-metric and be done with it.

I am very happy with my $40 Chinese made DC Clamp meter.
http://www.amazon.com/Uni-T-UT204-Auto-Ranging-Handheld-Multimeter/dp/B00FEBSJ58/ref=sr_1_5?ie=UTF8&qid=1458395713&sr=8-5&keywords=UNI-T+clamp+meter

When choosing a clampmeter, check carefully to be sure it measures DC current.
The ones that only measure AC current are much cheaper.

75 MV means that the rated current there is .075 volt drop across it.

I=E/R so R-E/I the resistance is 0.075/rated amprage.. Or if it is a 200 amp shunt, then .075/200.. You will read dead short on your average Multi-Meter. takes very special hardware to read that close to zero.

Measure the millivolts under load, do the math and compare the figures

Dang, you'd think it was going in a nuclear submarine.

Happy Prospector wrote:
Dang, you'd think it was going in a nuclear submarine.

Camping is very serious business....