Shunts...are they "trimmable"?!

Ham

1 kW
Joined
Feb 18, 2016
Messages
498
Hi Folks,

Just a quickie for the smart people in here:

I have a new bigger shunt for my build and I am wondering, as it is rather large and bulky (in comparison to the old one), if it is possible to cut the ends off (the areas where bolts can be passed through for cable connections) so long as the centre resistance bars material is left untouched or would that just balls the whole thing up?

link for an idea of what I am talking about:) https://www.ebay.co.uk/itm/Shunt-300A-50mV/283188747091?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2648


Thanks
 
As long as you don't remove any material from between the two small shunt sensing screws, you should be okay. Any conductor material removed from elsewhere should be appropriate for the current requirements of your specific controller.
 
Thanks Daniel, the capacity of this shunt is waaay over and above (300a cnt.) what the CA3 limit and Castle HV160 limits will be set to (160amp)...the one in there right now is tiny any rated for 50 continuous and 100a peak so hopefully trimming will still leave it over engineered for it's purpose.

I'll hold off for a while to give others a chance to scream NOOO don't do it before taking a cutting disc to it!
 
Even if you were to alter the central portion of the shunt, as long as you know the new resistance value (it's easy to test), you'll be alright.
 
If you cut it off, you might affect the current distribution in the actual resistance elements slightly. Like danielrlee pointed out, as long as you don't remove any between the sensing wire connections and the resistance elements, it should work fine.

Something like pictured below should be OK. You would need to figure out how to attach your wires though.

 
Thank you!

The initial thought process is to solder the main battery negative lead along one of the faces of the shunt...
 
Ham said:
Thank you!

The initial thought process is to solder the main battery negative lead along one of the faces of the shunt...

That's probably what I would do. It will take a LOT of heat to solder on that thing though. Use a really big iron.
I would avoid using a torch as you might get it hot enough to melt the solder that holds the resistance elements into the block. You should probably clamp it so the heated part faces up so it won't tend to fall apart if those connections melt.

Another approach would be to drill holes on the opposite side from the sensing wire screws and use a bolted connection.
 
Food for thought for sure, I have been using a 200w iron for most things so i will give it a go before going the bolted route.

Great heads up about the bars falling out!
 
Ham said:
Thank you!

The initial thought process is to solder the main battery negative lead along one of the faces of the shunt...

Why wouldn't you bolt to it?
 
Chalo said:
Ham said:
Thank you!

The initial thought process is to solder the main battery negative lead along one of the faces of the shunt...

Why wouldn't you bolt to it?

Just for tidiness I guess...plus I have spent a long time practicing and kind of enjoy it now :) Plus I have everything I need to solder and no high rated eye clamp thingies!
 
Ham said:
Chalo said:
Ham said:
Thank you!

The initial thought process is to solder the main battery negative lead along one of the faces of the shunt...

Why wouldn't you bolt to it?

Just for tidiness I guess...plus I have spent a long time practicing and kind of enjoy it now :) Plus I have everything I need to solder and no high rated eye clamp thingies!

I have done a lot of soldering, and I never enjoy soldering to something massive. You'll wick solder up into your wire and make it stiff. Maybe try spreading the strands out a bit, just above the section you want to solder, and dabbing some liquid paper into it as an anti-flux.

Me, I'd use a ring terminal every time.
 
Thank you. I'll have a look around and see if I can find any rated high enough.
 
Back
Top