How to Install Voltmeter

[crashkahuna]

I have a simple Blue Sea analog voltmeter that has switch for battery 1, 2 or 3. I think it has a + wire for each and a common -. What is best way to hook this up so I can monitor either of my 2 batteries just with this meter? Thanks.

[Blue Stocking]

Whats the problem? You described the layout in your post.

[crashkahuna]

I guess I am asking does it go + wire to each battery and other wire to a battery negative (which?) or to negative on battery switch?

[Blue Stocking]

Where you pick up your +'s depends on your wiring layout. What you want to avoid is any long runs of small gauge wire, which will have voltage drop loss.
Best bet is directly from each battery terminal to meter.
Your -'s should all be common, so find the shortest run, and use a suitable gauge wire.

[St. Elsewhere]

Fuses should be installed near each battery. The meter should have installation instructions with such details.

[hellosailor]

"What is best way to hook this up so I can monitor either of my 2 batteries"
The common wire to the common ground point at your battery bank, or on your engine block, whichever you use. And the hot wires, one each to the two battery positive posts, not the battery switch. The voltage at the switch may be .1v less than at the battery just from wiring losses.
You'd want to use tinned wire, so you don't get false readings from the wiring corroding as it ages. And, just in case, install a small fuse in each positive wire right at the battery connection. Something like 1/10th of an amp, preferably fast blow type, probably will do. Anything under 1 amp should be fine for those fuses, you just want it to blow before the wiring itself can. Most setups wouldn't bother fusing those lines--but they really should be fused.
BS tech support should be able to go over anything with you if you gave them a call.

[crashkahuna]

Thanks. Should be easy enough. Good idea about fuse. It was already installed but never connected to anything so I didn't have the instructions.

[skipmac]

Originally Posted by crashkahuna

I guess I am asking does it go + wire to each battery and other wire to a battery negative (which?) or to negative on battery switch?

Are you sure your battery switch has a negative? All the ones I've ever used only switched the positive side.

[Jim Cate]

Don't think that you have to worry about voltage drop in the sense wires to the batteries. The voltmeter draws so little current that this is not an issue.

JIm

[Capt.Don]

My panel voltmeter has a 1-2-3 selector switch for monitoring up to 3 banks of batteries. 1 and 3 were wired directly to house and start positive battery terminals. 2 was wired somewhere after the battery selector switch, I guess to monitor the house voltage, whether house, start or both. FWIW, I swapped 2 and 3, to be consistent with the battery selector switch. House was fused, and I added a fuse to the Start battery. Also, my voltmeter has an calibration screw, which I adjusted to match my hand-held voltmeter. I don't recall the wire gauge, but it was the same size as most of the wires going to the electronics. It wasn't really small wire.

[crashkahuna]

Originally Posted by skipmac

Are you sure your battery switch has a negative? All the ones I've ever used only switched the positive side.

You are right - I guess I meant negative bus.

[hellosailor]

Jim-
"Don't think that you have to worry about voltage drop in the sense wires to the batteries. The voltmeter draws so little current that this is not an issue."
True enough, but one can easily pick up some 24AWG stranded wire, sold for many small-signal applications and "enough" to do this job. (I've gotten good use from a big spool of it, tinned, twisted pair.) And then, easily lose half the strands at each end while trying to connect them. A larger wire is simply going to be more robust and less likely to suffer any of the problems (cuts, corrosion, oxidation) that would be problems on "good enough" smaller wires.

[GordMay]

Originally Posted by hellosailor

... A larger wire is simply going to be more robust and less likely to suffer any of the problems (cuts, corrosion, oxidation) that would be problems on "good enough" smaller wires.

Indeed.
Which may explain, in part, why the minimum wire size permitted by ABYC is #16 AWG, regardless of load current.

[Jim Cate]

Originally Posted by GordMay

Indeed.
Which may explain, in part, why the minimum wire size permitted by ABYC is #16 AWG, regardless of load current.

That's interesting, Gord... but what about the myriad wires supplied by the electronics OEMs? Except for the power leads, none of the wires in such equipment are that large and there are heaps of them on any modern boat. I submit that the sense wires for a voltmeter fall into a similar category.

The suggestion of using tinned twisted pair cable in this application is a good one IMO.

Cheers,