Cranking current measured

[cranetruck]

FWIW, temporarily wired in a current shunt and was able to measure the current draw during the cranking of the 8x8 engine. The big multifuel starts very easily, but I noted a reading of about 360 amps for a couple of seconds.

The newly installed Chargetek 500 had been plugged in overnight, so the batteries were fully charged.

(With a shunt in the circuit, the voltage drop is measured across it and converted to amps. This particular shunt is calibrated to read 50 mV for a current of 300 amps and my max reading was 60 mV.)

 

[rosco]

I have had for some time now, a clamp-meter made by Fluke, that also measures DC current. It records the current draw. I have found it to be invaluable in trouble shooting, particularly on vehicles. In particular, current can be measured without disconnecting anything.

Lee in Alaska

 

[cranetruck]

Agree with you Lee.
There are a couple of advantages with the shunt, one is that it was a lot cheaper than a Fluke clamp-on and it can be left in permanently for a gauge to display cranking current, a measure of the health of the starting system. The starting system has very few monitoring devices and is often a problem (because of it).
The cranking current is directly related to the cranking rpm and in my case 360 amps is approx 200 rpm, which is just right.

 

[papercu]

shunt

I have a shunt on ebay if anyone needs one. ebay item number 200217842954 or try the link. TIA, Wayne

http://cgi.ebay.com/50MV-500-Amp-In...ryZ78182QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[emmado22]

Whats the purpose of the shunt?? there is one of them in every Humvee out there...

 

[papercu]

shunt

They are use with the ammeter. Wayne

50A shunt resistor
An ammeter shunt is used to measure current values too large to be directly measured by an ammeter. In this case a manganin resistor of accurately-known resistance, the shunt, is placed in series with the load so that nearly all of the current to be measured will flow through it. The voltage drop across it is proportional to the current flowing and since the resistance is known, an ammeter connected across the shunt can be scaled to read the current value.

In order not to disrupt the circuit, the resistance of the shunt is normally very small. Shunts are rated by maximum current and voltage drop at that current, for example, a 500 A/75 mV shunt would have a maximum allowable current of 500 amps and at that current the voltage drop would be 75 millivolts. By convention, most shunts are designed to drop 75 mV when operating at their full rated current and most "ammeters" are actually designed as voltmeters that reach full-scale deflection at 75 mV.

http://en.wikipedia.org/wiki/Shunt_(electrical)

 

[cranetruck]

Whats the purpose of the shunt?? there is one of them in every Humvee out there...

Looked into it and the shunt is one of the "transducers" used when troubleshooting the electricals on the hmmwv . It is permanently installed and permits the measurement of the cranking current. It is wired to the DCA connector.
What does DCA stand for anyway?