Shunt wiring

[daletournier]

Originally Posted by transmitterdan

Guys,

Can you get a shunt like the OP had hooked up "wrong" to give some reading? Yes, and if that's a definition of "it works" then ok, it will work. But there is significant resistance in the studs and the brass block. So there is no good way to get an accurate reading using the big studs. For a small current shunt of 25-50A the error will be negligible. But for a big 250-500A shunt the error will be significant. That's my definition of "it won't work".

If the small screw holes are damaged the "best" field fix would be to drill out and tap to next larger screw size. Or drill and tap same size holes on opposite side of shunt. All cruisers ought to have a small set of drills and taps IMO.

Hi Transmitten, not trying to be difficult and I appreciate your knowledge in the thread.
I have drills and taps, I'm an ex mechanic. But truly I couldn't be bothered because I just can't notice the inaccuracy. I just had the generator on (no other input) and the reading on the battery charger was real close to the xantrex. The xantrex was a a amp or so less, that's all, this is while pumping in 50a. I was running lights etc at the time.
If there's a difference between where I have them now and where they were it's a small one. My habits are consistent, the xantrex reads the same in the mornings etc. It's easily good enough to gauge where I'm at when I also take voltage into consideration.

[transmitterdan]

And I am just trying to help. Sooner or later the big bolts will shift resistance and then the current reading will be wrong. I have been using big shunts like this for decades so having seen problems am just giving friendly advice.

[Wotname]

Originally Posted by transmitterdan

And I am just trying to help. Sooner or later the big bolts will shift resistance and then the current reading will be wrong. I have been using big shunts like this for decades so having seen problems am just giving friendly advice.

[daletournier]

Originally Posted by transmitterdan

And I am just trying to help. Sooner or later the big bolts will shift resistance and then the current reading will be wrong. I have been using big shunts like this for decades so having seen problems am just giving friendly advice.

I appreciate that. I know more about shunts than I did a couple of days back.

[Bermuda Forte]

Installing a 50 amp shunt w/analog 12V DC meter as part of new panel/rewiring project. Instructions state that it goes on the positive side with 1 amp fuses on each sensing wire. I plan to install it on the negative side, which I know is fine, but I’m assuming I don’t need to fuse these wires. Can anyone confirm? Many thanks!

[transmitterdan]

Originally Posted by Bermuda Forte

Installing a 50 amp shunt w/analog 12V DC meter as part of new panel/rewiring project. Instructions state that it goes on the positive side with 1 amp fuses on each sensing wire. I plan to install it on the negative side, which I know is fine, but I’m assuming I don’t need to fuse these wires. Can anyone confirm? Many thanks!

I would still fuse them. It’s cheap insurance. If you accidentally short from the meter to anything (+ or -) there could be high current in the meter wires.

[Dsanduril]

As TD says, convention is to fuse and insulate on the negative side just as if it were the positive side. If your negative cable gets disconnected at the battery terminal while the positive is still connnected you will have full potential throughout the wiring system. I know, sounds unlikely, but it happens and that’s why the safety gear is there.

[Bermuda Forte]

Thanks much. Fuse it is.