Largerr shunt for power?

ebike11

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Hi guys..im using a Grin shunt with my CA which is connected to a sabvoton 72200 and qs205.
I believe Grin told me the shunt is good up to 100A.
Im putting more amps through it so would a larger shunt help at all or not much?
Would there be any power increase?
Plan on getting a 150A or 200A shunt.
Thanks
 
Which grin shunt? I have cooked off the standard external shunt used with the stand alone CA. Not sure if flaky andersons got it hotter than it should have been, or if it was just the shunt. Never put more than 40 amps of 72v through it. But I do believe they can and do age if you run enough power to make them warm.

You likely need a big shunt, for the stuff you like.
 
dogman dan said:
Which grin shunt? I have cooked off the standard external shunt used with the stand alone CA. Not sure if flaky andersons got it hotter than it should have been, or if it was just the shunt. Never put more than 40 amps of 72v through it. But I do believe they can and do age if you run enough power to make them warm.

You likely need a big shunt, for the stuff you like.

Im also using the external shunt since my controller doesnt have a CA connector. This one here

https://www.ebikes.ca/shop/electric-bicycle-parts/ca-accessories/shunts/shunt-ca3.html

Ive been running 100A through it..so far so good haha. But i wanna get a bigger one to be safe. I thought Grin said 100A but that is max. but im not sure if it mentioned the voltage
 
The Grin Shunt is a 50A shunt, that can handle 100A peaks. There is no voltage rating as shunt resistors can handle thousands of volts.

If you plan to really use the full power of that Q205, I would look for a shunt who's continuous power rating is the same as the Max pow you plan to pull. Peak power usually means under a second. Continuous power means they can handle that all day long. If you plan to run full power of your motor up a hill, you're going to pull max power from your motor far longer than the peak rating of a shunt was meant for, and should use continuous power ratings to size your shunt.
 
Drunkskunk said:
The Grin Shunt is a 50A shunt, that can handle 100A peaks. There is no voltage rating as shunt resistors can handle thousands of volts.

If you plan to really use the full power of that Q205, I would look for a shunt who's continuous power rating is the same as the Max pow you plan to pull. Peak power usually means under a second. Continuous power means they can handle that all day long. If you plan to run full power of your motor up a hill, you're going to pull max power from your motor far longer than the peak rating of a shunt was meant for, and should use continuous power ratings to size your shunt.

Ok thanks for those tips!
What would happen to a shunt if too much power is going through it with the shunt being a smaller size?

When you say look for a shunt in the motors power rangr..do you mean Continuous Amps? or watts?
My sabvoton can only 200A max.

Thanks!
 
ebike11 said:
Do larger shunts allow for more power? Increased top speed?

I think it is marginal, the loss or whatnot. The V=IR drop is not that much, and that is how shunts are designed.. to handle it ... and not put a bottleneck on the system.. so to speak,m I think. I read once y9ou can heat sink the small Grin shunt. That is the one I use, is the bottleneck of my system ( 12g 6" section vs 8 ga everywhere else) ... and is working fine in my setup. I got a 3.3Kw 50A contin 100A peak controller.. and it is fine but if I was going bigger I would want something better. I need one in the range of 300A also, ( well, two actually) and I want a nice modern looking one or something.... some kind of modular ones with good contact connects not those old fashioned ring terminals. But whatever. Dont let the shunt be a bottleneck, no heat rise. I have read about putting a heatsink on the back of a Grin modular shunt with thermal transfer paste after you shave off the black plastic on the flat side. To handle more current.. and I have a good low IR pack that the shunt doesn't notice. I dont have power or heat problems.

I have also thought about making a potted shunt with the same design and pinout as the smaller Grin shunt, but with a 250A ~ shunt... ie. one off clone Justins design. With larger shunt, and some black epoxy potting in a cut off milk jug base. Whoolah 250A shunt with potted weatherproofing and all the pinouts you need for the CA3 and the controller Th input. W/ large gauge main wires.

Some old cars also have free shunts in them, on the fenders, in junkyards.. and shunt trip breakers at industrial scrap yards... have shunts in them lol. Someone alsoonce just told me to use a small chunk of undersized wire you calculated the V=IR mV drop @ I.... based on the math and known variables only.
 
DogDipstick said:
ebike11 said:
Do larger shunts allow for more power? Increased top speed?

I think it is marginal, the loss or whatnot. The V=IR drop is not that much, and that is how shunts are designed.. to handle it ... and not put a bottleneck on the system.. so to speak,m I think. I read once y9ou can heat sink the small Grin shunt. That is the one I use, is the bottleneck of my system ( 12g 6" section vs 8 ga everywhere else) ... and is working fine in my setup. I got a 3.3Kw 50A contin 100A peak controller.. and it is fine but if I was going bigger I would want something better. I need one in the range of 300A also, ( well, two actually) and I want a nice modern looking one or something.... some kind of modular ones with good contact connects not those old fashioned ring terminals. But whatever. Dont let the shunt be a bottleneck, no heat rise. I have read about putting a heatsink on the back of a Grin modular shunt with thermal transfer paste after you shave off the black plastic on the flat side. To handle more current.. and I have a good low IR pack that the shunt doesn't notice. I dont have power or heat problems.

I have also thought about making a potted shunt with the same design and pinout as the smaller Grin shunt, but with a 250A ~ shunt... ie. one off clone Justins design. With larger shunt, and some black epoxy potting in a cut off milk jug base. Whoolah 250A shunt with potted weatherproofing and all the pinouts you need for the CA3 and the controller Th input. W/ large gauge main wires.

Some old cars also have free shunts in them, on the fenders, in junkyards.. and shunt trip breakers at industrial scrap yards... have shunts in them lol. Someone alsoonce just told me to use a small chunk of undersized wire you calculated the V=IR mV drop @ I.... based on the math and known variables only.

This shunt looks simple and cheap..it would be hidden anyway in the frame
https://a.aliexpress.com/_dVo9MMi
Is this the old style you talked about?
Also when it says 200A rating does it mean it will work properly for any Amps you draw from 0 to 200 or its only meant to be used for a powerful system which much be closer to the upper region of 200A?
Thanks!
 
While using a larger shunt will give a little bit more , Why not go for the max. Use a hall effect amp meter. They do not heat up and no resistance , because there isn't any break in the wire. Vvvvery little power draw and no heat at all. :mrgreen: :mrgreen:

Example https://www.ebay.com/itm/DC-5-120V-100A-Digital-Voltmeter-Current-Voltage-Amp-Meter-w-Hall-Effect-Sensor/264765296492?hash=item3da53dcf6c:g:Qm0AAOSwx09e6BsR

JimJr
 
ebike11 said:
Do larger shunts allow for more power? Increased top speed?

No. A shunt is one way to convert a current signal, using a known resistance, into a voltage signal, which can then be measured to compute the current flow. In high voltage AC applications, current transformers and voltage transformers are used to do the same. The cycle analyst or controller uses that information to set current limits. For the controller, changing the shunt resistance, without modifying the circuitry that receives the voltage signal, is just fooling the current limiting circuits of the controller into thinking less current is flowing, so the circuit allows more actual current to flow. For the shunt the CA uses for monitoring, you need to adjust the shunt resistance in the setup, in order to obtain an accurate current (and therefore power) readings, but won't affect performance. There would be no reason to change the CA shunt, unless you are flowing so much current past the rating, to render the voltage signal inaccurate (since it will heat up, and resistance with rise).
If they CA is using the same shunt signal as the controller, then modifying the shunt can fool the controller circuits to allow more current to flow, but you'd want to adjust the CA settings in order to get accurate readings. Is that your goal, or just to ensure the properly sized shunt for the CA?
 
Using a shunt bigger than the controller might get confused on the feedback since that shunt puts out between 75 to 100 millavolts
at 100 amps , the hall effect coil puts out 4 volts . Use a 10k potentiometer to adjust to the voltage needed.

The Hall effect transducer draws only what is needed for the circuit , very little power, A regular shunt at full capacity draws enough to almost to light a cigarette continuously at full load. A waste of battery capacity and heating up everything around it.

As for the controller using the input to control the amp output is doubtful , Its after the fact. Its much easier to do it before the
horse leaves the barn. the shunt is probably for reference for the display .

Most of the people designing these controllers doing it to get a end result and don't care about wasting energy, just cheap as
possible.


The resistance shunt is only suposed to used as refference for a short peroid of time , like two minuits because of thermal drift.

If the controller is not a issue , a larger shunt will allow more watts to pass thru , because less heat generated for resistance heat
rise

JimJr
 
E-HP said:
ebike11 said:
Do larger shunts allow for more power? Increased top speed?

No. A shunt is one way to convert a current signal, using a known resistance, into a voltage signal, which can then be measured to compute the current flow. In high voltage AC applications, current transformers and voltage transformers are used to do the same. The cycle analyst or controller uses that information to set current limits. For the controller, changing the shunt resistance, without modifying the circuitry that receives the voltage signal, is just fooling the current limiting circuits of the controller into thinking less current is flowing, so the circuit allows more actual current to flow. For the shunt the CA uses for monitoring, you need to adjust the shunt resistance in the setup, in order to obtain an accurate current (and therefore power) readings, but won't affect performance. There would be no reason to change the CA shunt, unless you are flowing so much current past the rating, to render the voltage signal inaccurate (since it will heat up, and resistance with rise).
If they CA is using the same shunt signal as the controller, then modifying the shunt can fool the controller circuits to allow more current to flow, but you'd want to adjust the CA settings in order to get accurate readings. Is that your goal, or just to ensure the properly sized shunt for the CA?

Hi! Im trying to find the proper shunt for my CA..between it and the controller. I have a qs205 and sabvoton that puts out 150A to 200A.
The Grin shunt is small and rated 50A continuous and 100A max. So I want to get a bigger one so there will be no issues.
Im thinking of the 200A one that i linked to. I wont be going over 200A
 
If your objective is to stuff stupid power through your system, the best thing is to eliminate components that add points of failure and don’t advance your objective. In this case, that’s the Cycle Analyst and its shunt. If you need a fuse, put in a fuse. Otherwise, use short runs of big wire and a minimum number of big connectors, and that’s all. Things like a throttle and a voltmeter and a GPS speedometer don’t stand in the path of current flow, so those are the things you should use while leaving the motor power circuit minimal and short.
 
jhaz6471 said:
Using a shunt bigger than the controller might get confused on the feedback since that shunt puts out between 75 to 100 millavolts
at 100 amps , the hall effect coil puts out 4 volts . Use a 10k potentiometer to adjust to the voltage needed.

The Hall effect transducer draws only what is needed for the circuit , very little power, A regular shunt at full capacity draws enough to almost to light a cigarette continuously at full load. A waste of battery capacity and heating up everything around it.

As for the controller using the input to control the amp output is doubtful , Its after the fact. Its much easier to do it before the
horse leaves the barn. the shunt is probably for reference for the display .

Most of the people designing these controllers doing it to get a end result and don't care about wasting energy, just cheap as
possible.


The resistance shunt is only suposed to used as refference for a short peroid of time , like two minuits because of thermal drift.

If the controller is not a issue , a larger shunt will allow more watts to pass thru , because less heat generated for resistance heat
rise

JimJr

H! Im not worried about cost or saving power. Actually i dont care about wasting power if it gives me more top speed. Thats my main goal so I want to eliminate any weak points or wiring that may bottleneck the power. The grin CA shunt is small but is good for most applications.
I have a sabviton unlocked to 200A so i thought I had to get a shunt rated at 200A
 
Balmorhea said:
If your objective is to stuff stupid power through your system, the best thing is to eliminate components that add points of failure and don’t advance your objective. In this case, that’s the Cycle Analyst and its shunt. If you need a fuse, put in a fuse. Otherwise, use short runs of big wire and a minimum number of big connectors, and that’s all. Things like a throttle and a voltmeter and a GPS speedometer don’t stand in the path of current flow, so those are the things you should use while leaving the motor power circuit minimal and short.

Thx for the reply...yes makes sense..but i really wanna have big power with the CA. It provides me with so many options and info. I love it.
Should i go thicker than 10awg?? Thats what i run at the moment
 
ebike11 said:
Hi! Im trying to find the proper shunt for my CA..between it and the controller. I have a qs205 and sabvoton that puts out 150A to 200A.
The Grin shunt is small and rated 50A continuous and 100A max. So I want to get a bigger one so there will be no issues.
Im thinking of the 200A one that i linked to. I wont be going over 200A
$15 on ebay. You just need to change the shunt resistance in the CA setup.
 
Try using : http://www.gtsparkplugs.com/WireSizeCalc.html To get the amps you want at the voltage you need . divide your voltage
by 12v and multiply the result with the number of amps the calculator give you. 72v at 150a would be 4.8 feet of total length of
circuit with a 10 gauge wire

The 200a shunt will do better, but is still a resister , a straight shot is = to max amps output. For wanting the amp meter the hall effect
will achieve that.

JimJr
 
jhaz6471 said:
Try using : http://www.gtsparkplugs.com/WireSizeCalc.html To get the amps you want at the voltage you need . divide your voltage
by 12v and multiply the result with the number of amps the calculator give you. 72v at 150a would be 4.8 feet of total length of
circuit with a 10 gauge wire

The 200a shunt will do better, but is still a resister , a straight shot is = to max amps output. For wanting the amp meter the hall effect
will achieve that.

JimJr

Thx for the info again..i will run 24s so 100V fully charged at 200A which is max.amps. i gotta connect multiple lipo packs together to get up to 100V so i cant estimate the wire length in a straight line.
Id like to bypass the shunt but i need it to wire the jst plug to because my controller does not support the JST of a CA
 
E-HP said:
ebike11 said:
Hi! Im trying to find the proper shunt for my CA..between it and the controller. I have a qs205 and sabvoton that puts out 150A to 200A.
The Grin shunt is small and rated 50A continuous and 100A max. So I want to get a bigger one so there will be no issues.
Im thinking of the 200A one that i linked to. I wont be going over 200A
$15 on ebay. You just need to change the shunt resistance in the CA setup.

I ordered that 200A shunt on aliexpress..i dont use ebay coz of high shipping to Asia
Yes i seen that i need to maybe change to Hi Mode in the settings for the CA to read the watts correctly
 
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