Volt Meter Idea

yurtle

Here's how I'm currently wiring up my Alltrax Ex-Ray volt meter. I'm hooking up nine fused wires to a mil. spec. rotary switch, which has an adjustable stop to allow two (one would be silly) to twelve positions, two poles. I set mine for ten positions: off, batteries 1 - 8, and pack.

I currently have the warning and alarm set so that both LEDs flash when I do this (low voltage), but this is just an easy and free (discounting labor) way of monitoring each battery under load, while driving around.

Nice to have hoarded clutter lying around!

Crazy?

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BGW

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yurtle

Besides, I had to find something to fill the space where the old volt meter was. That's where my rotary switch will go. I've already narrowed my choice of knobs down to a couple: old-school, new-fangled, Radio Shack.

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JohnnieB

Old-School knob w/pointer.

And some demented musings from another Crazy.

Move the stop out to twelve and use the two additional positions to monitor voltage drop across the Armature and the Stator, or across F/R contacts.

Also, you're going to be connecting wires to every battery and to keep the smaller terminal lugs from interfering with the high current connections between the battery cables and the battery terminals, use stud extenders to connect the light weight stuff.

yurtle

Here's the knob I've chosen. I'm also using ring terminals, so I'll have metal nut, to metal ring terminal, to metal lug, to metal battery terminal, so I think I'll be OK without the stud extenders. I did this on my last wiring job, where I used three 12 volt circuits, and never had any overheating issues.

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JohnnieB

Great minds think alike.

I lean towards overkill with high current connections. Each metal to metal interface is imperfect, so the fewer interfaces the better for maximum current transfer.
I haven't done it yet, but the ring terminals from the charger receptacle are going to end up on stud extensions.

The stacking order you listed is the way I would do it if stud extenders aren't used.

FWIW: I had to replace a transformer in an X-Ray machine because the ring terminal for a monitoring circuit was stacked between the main cable and the transformer terminal, vaporized and the plasma cut nearly through the stud when a megawatt (200KV @ 5A) passed through it. Needless to say, the repairman that didn't read the manual got some remedial education from my size 16 boot.

yurtle

Another way to do this might be to solder the small gauge wires and the 2 AWG cables in the same lug. I already have my 2 AWG welding cable, silver solder and flux, but I'm still waiting on my lugs and "gooey" heat-shrink - red and black - to arrive.

yurtle

I've rethought the order of the rotary switch. I had highjacked the toggle switch that was previously used for my stereo, to kill the backlight, assuming it might be annoying at night. I'm gonna rewire it back to the stereo and re-sequence my rotary to be off, pack, batteries 1-8, then who knows.

You gotta love the din-rail fuse blocks. You'll notice I have 11 Weidmullers, while I only need nine for the battery voltage. This has got to be one of the most expensive fuse block installations in a buggy. I looked at various marine and automotive fuse blocks, but most have a common hot, while I need an independent in and out.

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yurtle

FWIW, I think using a lead base, with a SS stud and SS nut is far from ideal for a high duty cycle, high current connection. Cars are different, as they have a low duty cycle. Buggies should have a better design, especially since we've read of numerous failures. The torque requirements on almost all industrial high current connections are quite high. Batteries with a stud cast in lead have a VERY low tolerance for over torquing, not to mention the fact that lead isn't the best conductor for high current applications. Most of what I see at work is silver plated copper.

JohnnieB

I hear you on the lead w/SS stud & nut being far from ideal, but it's what we've got to live with until something better becomes readily available.

I'm going to be replacing my batteries in the not too distant future and I'm considering getting ones with EUT or UT terminals (Lead post with a hole through it) and use SS nuts and bolts.
That way I can put the heavier lugs between the nut and the post and the lighter stuff, if any, on the other side between the bolt head and the post. Or maybe the other way around.
Than I can use two wrenches and put a bit more torque on the connection as long as I don't put any angular torque on the lead post, which will still be fragile.

Right now I working on a way to mount an Ammeter shunt (75 mV @ 500A) so it doesn't wiggle or put weight on the battery terminal while not blocking air flow through it. I had it all figured out and was getting ready to do some cutting, than I discovered the plastic I was making the bracket out of, was conductive. Now I've got to search through my stash of "might be useful someday" stuff some more.

yurtle

My rule of thumb for conductive plastics is to microwave them. That's good for HF AC, but overkill for chopped-DC. My experience is that black is usually bad and white is usually good.

Cutting boards from WALMART are usually quite good, even at HV HF.