Ammeter Wiring

[RichLo]

CORRECTED DRAWING ATTACHED

This time in parallel without the dead short to ground.

The only thing this will do is measure the current flow between the batteries (likely nothing unless one is bad).

 

[RawbDidIt]

Oh, I didn't even think of the draw from the starter, that's an excellent point. To your point that would read what's coming from the alternator, but if you're drawing more than the alternator can provide it's important to know that as well. The only way to remove the draw of the starter from the equation would be to read from the positive side. Are you putting a solenoid switch in to keep the batteries isolated until the key is on? If so, there's 2 ways to do this. Read just the amps coming from the alternator and make sure your alternator is beefy enough to provide all the power you need even at idle, but you'll never know what you're drawing when the truck isn't running. The other way to do it would be my preferred way with a solenoid switch. You'd have to install 2 ammeters, 1 reading each battery with the starter feed wire bypassing the ammeters.

If you're not installing a solenoid switch (if you're like me and never run loads with the truck off, this will work fine) you'd run all positive leads to a central connection and run the ammeter there, then branch it to all of your loads. The starter would have to have a separate lead.

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[ME TOO 2]

Thanks to both of you (RawbDidit & RichLo) for taking an interest
Since I do not run loads when the engine is off it seems to me the best bet is RawbDidit's version without the solenoids.
My reason reason for adding an ammeter is to monitor the overall state of charge/discharge when running .
I have no need to monitor individual accessories nor am I seeking out parasitic current draw
Also, as I think about this; measuring the starter load is not very useful because IMO watching the battery voltage drop on a voltmeter when starting is a better indication of battery health than an ammeter could ever be.
Feel free to disagree, please.

Any thoughts on shunts versus "around the wire" current sensors appreciated also

 

[RawbDidIt]

Glad to help.

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[RichLo]

Also glad to help, I am actually in the process of figuring out where to wire an ammeter on my snowplow truck so this thread is helping me think deeper about it also. Except I have a few more conditions to think about (two alternators, two batteries, in-cab battery selector, already pre-hacked wiring by a PO, and a snow plow pump that draws the same current as a starter, lol)

The bottom drawing below 'option 1' is essentially what you are looking for, the tough part is finding just 1 wire that supplies all of the vehicles power then branches off after that. Unless you make a junction box of some sort that will take all of the current positives (small wires on the starter solenoid, alternator output, all the relays on the firewall, etc). Then take just one wire from the batteries and run it through the ammeter then to that junction box.

 

[ME TOO 2]

Also glad to help, I am actually in the process of figuring out where to wire an ammeter on my snowplow truck so this thread is helping me think deeper about it also. Except I have a few more conditions to think about (two alternators, two batteries, in-cab battery selector, already pre-hacked wiring by a PO, and a snow plow pump that draws the same current as a starter, lol)

The bottom drawing below 'option 1' is essentially what you are looking for, the tough part is finding just 1 wire that supplies all of the vehicles power then branches off after that. Unless you make a junction box of some sort that will take all of the current positives (small wires on the starter solenoid, alternator output, all the relays on the firewall, etc). Then take just one wire from the batteries and run it through the ammeter then to that junction box.

 

[ME TOO 2]

Thanks
What if I were to do the same thing but instead of the positive; consolidating the grounds onto 1 bus bar?

BTW
Your project eems to be taking on nautical proportions.
Something like the multiple batteries, charging circuits and isolation of small yachts

 

[RichLo]

Well, like I said earlier, Generally I like dealing with negatives in these kinds of circumstances however in this case trying to isolate just the starter from the rest of the devices is virtually impossible to do through grounds... if you think about how many short ground wires there are going to the frame or body and how many things ground themselves through their mounting surface without any wires it just isn't possible to do. With the positives though, you should be able to find everything pretty quickly coming out of the battery cable and starter solenoid.

And I never thought about my plow truck like a yacht before, lol, but I guess it is somewhat nautical. It does move water like a boat, just frozen water instead.

 

[RawbDidIt]

I was thinking something along the lines of using a small bus bar and then insulating it so it doesn't accidentally ground to anything.

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[ME TOO 2]

Well, like I said earlier, Generally I like dealing with negatives in these kinds of circumstances however in this case trying to isolate just the starter from the rest of the devices is virtually impossible to do through grounds... if you think about how many short ground wires there are going to the frame or body and how many things ground themselves through their mounting surface without any wires it just isn't possible to do. With the positives though, you should be able to find everything pretty quickly coming out of the battery cable and starter solenoid.

And I never thought about my plow truck like a yacht before, lol, but I guess it is somewhat nautical. It does move water like a boat, just frozen water instead.

Don't make the same mistake as many pleasure craft owners do; and name/refer to it as a girl.
Give it a masculine name appropriate to a true man 'o war.
No suggestions come to mind that would not offend someone, somewhere.
Thoughts!

Thanks for the advice, RichLo
Ed