Trimetric shunt/wire size question

You dont trust the voltage drop calculator?(and i have seen this done with a shunt). You dont have any distance to speak of. If it is strong enough,Go for it. I dont think .0079 voltage drop at 200 amps is gonna break the bank.

Good idea to use copper pipe. Here's mine.

BTW There is different wall thickness pipe for different maximum pressure. Unlikely to make any difference for that short distance.

Go with double thickness, it is not that expensive!

I made my own battery ends for the 000 welding cable that I installed for my 1,500 watt inverter and E-Meter - a early version of the Tri-Metric.

I also broke all the rules and used #18 gauge thermostat wire, not the recommended twisted pair wire. I did install 2 fuses, and all that. As I recall (going back to 1999 when I installed the e-meter) it has 2 each +12 wires, and 2 wires to the shunt (that are ground wires) and a ground wire for conducting power to the meter. Instructions say to connect one fuse first, then the second one. I guess it matters, but each time that I connected my battery, it all got connected at the same time.

It has worked great for many years. And many boondocking nights. I have gone to -120 amp hours and my 415 rated watt solar system can recharge that in one day. Any more than -120 AH, and I will run the generator in the morning to get the most amps per hour into the battery with my Trace 1500 watt inverter/charger rated at 70 amps output.

I have 4 golf cart batteries, rated at 440 AH total.

In truth, you could barely measure the voltage drop across 6" of copper wire. So it really does not matter. But materials are almost free, and time is hardly anything too.

I made my copper ends with 1/2" soft copper ACR tubing (I have lots sitting around) and flatten one end in a vice, then fold back about 1.5" and drill a 3/8" hole in it. Then had about 1" left at 1/2" diameter to insert the wire, and crimp it in the vice. None have failed in the 15 years that they have been in my motorhome.

Good luck with your projects!

Fred.

CA Traveler - Your photo and another that I found on-line were part of the inspiration for the solution I propose to use. I also plan to place a copper tab on the other end of the shunt so that I can easily attach the black lead of my portable charger to that and, I hope, keep a running tab of the SOC.

The copper pipe I plan to use as raw material is about 50 years old, and has a wall thickness about double that of the new pipe that I have.

Grizzzman - I'm not worried so much about voltage drop. I'm more worried about the bracket getting hot if it's cross sectional area is too small.

Wayne

Grizzzman - I'm not worried so much about voltage drop. I'm more worried about the bracket getting hot if it's cross sectional area is too small.

Wayne

OK where is this heat you are worried about coming from that due to its cross sectional being possibly to small? From the shunt? Or the battery at its end of charge cycle? An outside source?

If your are worried about to small a cross sectional area causing heat its due the the associated voltage drop that causes the heat you are worried about.

Grizzzman – My concern was at what point does the cross-sectional area of the conductor (the bracket) become small enough that it gets hot from resistance and perhaps burns in two? Same principle as a fuse.

But, I suppose if the voltage drop across it is so negligible, then the heat generated from the current passing through will also be negligible?

Wayne

Empty Nest, Soon wrote:
Grizzzman – My concern was at what point does the cross-sectional area of the conductor (the bracket) become small enough that it gets hot from resistance and perhaps burns in two? Same principle as a fuse.

But, I suppose if the voltage drop across it is so negligible, then the heat generated from the current passing through will also be negligible?

Wayne

Yep you got it. Voltage drop is the measurement used to decide if a conductor can handle the amps you want to put through it. And the higher the drop across the conductor the more heat it will generate. To put into perspective at 200 amps and 14 volts the voltage drop on your bracket would be about .0079. If you are using a 500 amp shunt and passing 200 amps at 14 volt its voltage drop would be .020. It is this calibrated voltage drop that the TM 2030 uses to decide how many amps are being used.

Good luck with your project

Grizzman – Thanks for that. It all makes sense now.

Yes, I’m using the 500 amp shunt. Given the 2000 watt inverter in my coach, I figure it is appropriate to allow for 200 amps from the batteries.

But I figure 200 amps is allowing a big cushion for safety. In practical terms, the biggest load passing through is likely to be 100 amps when charging from the inverter/charger. I don’t expect to use the microwave or other big appliance from the inverter when boondocking, so probably a toaster will be the biggest single draw.

When not boondocking, I would expect to be running directly on AC line voltage, so the batteries would be mostly out of the loop.

Wayne

You can do better than this I bet! :) (From last year-- now a little different but same sort of shmozzle.)

The copper pipe on the shunt is for charger clamps. The positive clamps go on the battery pos that has a flattened copper pipe extension to take more lugs--sort of a bus. This year I added a copper pipe to that whole mess for the positive charger clamps.

This year, I flattened more of the shunt's copper pipe shown there and drilled a hole up past the shunt so it can take a bolt for more neg lugs and still have some pipe above that for clamps.

The shunt bolts are too short to take many lugs, and besides the ideal is to have only one lug and go to a bus bar. Stacking lugs is not ideal (someday I will fix all that--sure I will :( )

I have the red-tab switch on the neg to the shunt for when I want to isolate the converter from the battery bank. Solar has its own switches for that. (on panel side of controller)



This year the T-1275s are in the truck camper leaving four-6s in the trailer and the Solar30 that fed the T-1275s is in the parts box for now.

I fiddle with my set-up quite often, so whatever you rig up at first should be considered just the first crack at it :) Guys like smk can get it right the first time and not touch it for years! Just weird. :)