Cycle Analyst abnormal readings

ebike11

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Moderator edit: This post and it's siblings were moved to the new thread ebike11 started about this problem, to give context and already existing info and troubleshooting steps to readers of the new thread.

Hi
Is anyone using a fardriver with external shunt and cycle analyst?
My power readings are all messed up and all over the place.

The CA read the power output fine with my older Sabvoton controller

Very strange...only swapped out the controllers. Shunt and CA werent touched
 
Based on that, it means the fardriver current is actually what you see from the CA, and any "messed up"-ness is something about the fardriver itself, which would mean it is not behaving the same as previous working controllers, either.

The only other typical possibility is if the current draw from the FD is so much higher than what the shunt you're using could handle that it the voltage across it is higher than the CA can correctly read.




ebike11 said:
Is anyone using a fardriver with external shunt and cycle analyst?
My power readings are all messed up and all over the place.

The CA read the power output fine with my older Sabvoton controller

Very strange...only swapped out the controllers. Shunt and CA werent touched
 
amberwolf said:
Based on that, it means the fardriver current is actually what you see from the CA, and any "messed up"-ness is something about the fardriver itself, which would mean it is not behaving the same as previous working controllers, either.

The only other typical possibility is if the current draw from the FD is so much higher than what the shunt you're using could handle that it the voltage across it is higher than the CA can correctly read.




ebike11 said:
Is anyone using a fardriver with external shunt and cycle analyst?
My power readings are all messed up and all over the place.

The CA read the power output fine with my older Sabvoton controller

Very strange...only swapped out the controllers. Shunt and CA werent touched

Hi thx for the reply
Actually the battery voltage reads perfectly fine on the CA. Its the current, Ah etc that are fluctuating super high numbers
 
j bjork said:
Current flow is read as a voltage drop over the shunt..
What Amberwolf says is if the current is too high for the shunt, the voltage (drop) reading will be too high.
It has nothing to do with what the voltage in the system are.

Hmmm but my battery amps are set at 210A and phase Amps at 450...similiar to what the settings were on my sabvoton.
 
ebike11 said:
Actually the battery voltage reads perfectly fine on the CA. Its the current, Ah etc that are fluctuating super high numbers
The voltage I referred to is the voltage the current generates across the shunt, which is what the CA is actually reading (it cant' directly read current).


But regardless, if the numbers fluctuate and the connections are all good, and it all works with anohter controller, then the new controller is actually drawing the currents you are seeing--the data is real.

If you know for certain that it is not real, then there is something wrong with the shunt settings in the CA, or connections to the shunt, etc., or as noted the current thru the shunt is so high it is beyond what the CA is able to read for that size shunt and you'd need a bigger one (or rather, one with a higher millivolt-per-amp spec).
 
ebike11 said:
Hmmm but my battery amps are set at 210A and phase Amps at 450...similiar to what the settings were on my sabvoton.
Doesn't matter what they are set to. Those are just settings and may not be obeyed strictly, depending on controller design and firmware design and robustness, and hardware design and build quality within the controller itself.

What matters is what they actually are. That's what the CA / shunt (or any other ammeter) is for, to test this and show you the reality. If the CA readings were valid previously, then they should be valid for this controller, too.
 
amberwolf said:
ebike11 said:
Actually the battery voltage reads perfectly fine on the CA. Its the current, Ah etc that are fluctuating super high numbers
The voltage I referred to is the voltage the current generates across the shunt, which is what the CA is actually reading (it cant' directly read current).


But regardless, if the numbers fluctuate and the connections are all good, and it all works with anohter controller, then the new controller is actually drawing the currents you are seeing--the data is real.

If you know for certain that it is not real, then there is something wrong with the shunt settings in the CA, or connections to the shunt, etc., or as noted the current thru the shunt is so high it is beyond what the CA is able to read for that size shunt and you'd need a bigger one (or rather, one with a higher millivolt-per-amp spec).

Ok i see.
I will also check my shunt connections along the negative power wire. Its an external shunt with the JST wired to it for the CA.
Im assuming the shunt has to facing a certain way when the JST wires are hooked up to it?? One end towrds controller and the other to the battery

Fyi..CA is reading 54kw standing still and only bike is powered on :)
 
ebike11 said:
I will also check my shunt connections along the negative power wire.
If there was a connection problem on the actual power wire, the system would not be operating correctly, and you'd have trouble with the motor spinning or driving the bike correctly.

If that is not happening, there wouldn't be a problem with the connection.

If it is happening, then you should also be telling us about those symptoms (and any others besides the suspected-incorrect readings in the CA).


Its an external shunt with the JST wired to it for the CA.
Im assuming the shunt has to facing a certain way when the JST wires are hooked up to it?? One end towrds controller and the other to the battery
The shunt itself isn't directional. but the thin (blue/white) wires from it to the CA do have an order. However, if you did not change this order when connecting the new controller, and did not unbolt the shunt completely (leaving the battery end connected to the battery cabling), then it cannot have changed so current direction will still be correct and so would the readings.

If you disconnected the shunt then you must make sure you reconnect it to the system the same way it was when it was working.


Fyi..CA is reading 54kw standing still and only bike is powered on :)

That usually means you need to "zero" the shunt current reading in the CA; it's in the advanced or shunt menus someplace. This tells the CA what the zero current reading should be.

If this problem keeps happening it means there is a connection problem between the CA and the shunt on those thin wires, so the voltage it reads between them is incorrect, so it displays the wrong current.
 
amberwolf said:
ebike11 said:
I will also check my shunt connections along the negative power wire.
If there was a connection problem on the actual power wire, the system would not be operating correctly, and you'd have trouble with the motor spinning or driving the bike correctly.

If that is not happening, there wouldn't be a problem with the connection.

If it is happening, then you should also be telling us about those symptoms (and any others besides the suspected-incorrect readings in the CA).


Its an external shunt with the JST wired to it for the CA.
Im assuming the shunt has to facing a certain way when the JST wires are hooked up to it?? One end towrds controller and the other to the battery
The shunt itself isn't directional. but the thin (blue/white) wires from it to the CA do have an order. However, if you did not change this order when connecting the new controller, and did not unbolt the shunt completely (leaving the battery end connected to the battery cabling), then it cannot have changed so current direction will still be correct and so would the readings.

If you disconnected the shunt then you must make sure you reconnect it to the system the same way it was when it was working.


Fyi..CA is reading 54kw standing still and only bike is powered on :)

That usually means you need to "zero" the shunt current reading in the CA; it's in the advanced or shunt menus someplace. This tells the CA what the zero current reading should be.

If this problem keeps happening it means there is a connection problem between the CA and the shunt on those thin wires, so the voltage it reads between them is incorrect, so it displays the wrong current.

Thanks again for your advice!
Yes previously when I was using my Sabvoton and installed the large external shunt, I had entered 0.375mOhm.
I set that number in the CA menu..one of the last screen in the Setup menu
Should I leave it at 0.375 or set it to Zero??
Thanks!
 
ebike11 said:
Yes previously when I was using my Sabvoton and installed the large external shunt, I had entered 0.375mOhm.
I set that number in the CA menu..one of the last screen in the Setup menu
Should I leave it at 0.375 or set it to Zero??
If the shunt settings and value are already correct, you don't change them.

(if they're not correct and haven't been changed from the previous controller then the readings you got with the previous controller would also not be correct).

You only need zero the shunt current reading when no current is actually flowing. You'll need to check the CA manual for the appropriate menu to find this in for your CA version; I don't know which one it would be for yours.
 
amberwolf said:
ebike11 said:
Yes previously when I was using my Sabvoton and installed the large external shunt, I had entered 0.375mOhm.
I set that number in the CA menu..one of the last screen in the Setup menu
Should I leave it at 0.375 or set it to Zero??
If the shunt settings and value are already correct, you don't change them.

(if they're not correct and haven't been changed from the previous controller then the readings you got with the previous controller would also not be correct).

You only need zero the shunt current reading when no current is actually flowing. You'll need to check the CA manual for the appropriate menu to find this in for your CA version; I don't know which one it would be for yours.

Ok thanks..ill double check all of my wiring this weekend
 
Hi everyone

I was hoping to get a rough idea of how big of an external shunt i need for my fardriver?
Its a pretty big controller.
The factory said its max. battery amps are 1350A but continuous is about half, so around 700A if what they are saying is accurate.
At the moment I plan on running 250~400A

I have a 200A 75mV shunt that was connected to my sabvoton previously and the cycle analyst read fine.

But with this controller connected to the same shunt, the readings and all over the place and the numbers are high. Just turning on the bike displays 54kw and 600Ah haha
Im think its because the shunt is too small. I will also double check the wire connections.

Would I need to match the continuous battery amps equal to the shunt? 700A 75mV?

Thanks!!
 
Why not just read the Wikipedia page for Ohm's law? Everything related to this specific issue, and much more, will become obvious.
 
Comrade said:
Why not just read the Wikipedia page for Ohm's law? Everything related to this specific issue, and much more, will become obvious.

Its a bit over my head regarding ohms:((
 
ebike11 said:
Would I need to match the continuous battery amps equal to the shunt? 700A 75mV?
Yes, if you plan to run continuous at that level (are you hauling a trailer?). Above the rating, the shunt will heat up, which will raise the resistance, and provide erroneous high readings. If you're only doing it for short bursts, then you don't need one that big and expensive, so 200A might be sufficient, but it sounds like you're already above that continuous.
 
E-HP said:
ebike11 said:
Would I need to match the continuous battery amps equal to the shunt? 700A 75mV?
Yes, if you plan to run continuous at that level (are you hauling a trailer?). Above the rating, the shunt will heat up, which will raise the resistance, and provide erroneous high readings. If you're only doing it for short bursts, then you don't need one that big and expensive, so 200A might be sufficient, but it sounds like you're already above that continuous.

Ok thanks
Would i get erroneous high readings if the shunt was too large for the actual control output or would i ger erroneous readings when only the shunt is too small?
 
ebike11 said:
E-HP said:
ebike11 said:
Would I need to match the continuous battery amps equal to the shunt? 700A 75mV?
Yes, if you plan to run continuous at that level (are you hauling a trailer?). Above the rating, the shunt will heat up, which will raise the resistance, and provide erroneous high readings. If you're only doing it for short bursts, then you don't need one that big and expensive, so 200A might be sufficient, but it sounds like you're already above that continuous.

Ok thanks
Would i get erroneous high readings if the shunt was too large for the actual control output or would i ger erroneous readings when only the shunt is too small?
Only too small will have the heat issue that will skew the reading. Those high amp shunts get pretty huge and expensive.

I'm using the 100A version of this one, which is about 1/3 the size of the other 100A shunt I have. Looks like they make a 500A version, and pretty cheap. Probably the same size as mine, but with more parallel shunt elements:
https://www.amazon.com/dp/B08477W6Q9?ref=ppx_yo2ov_dt_b_product_details&th=1
 
Why even use a shunt? You have a Cycle Analyst with a configurable shunt resistance. Just tap the power wire between the battery and the controller at each end and calibrate.
 
Comrade said:
Why even use a shunt? You have a Cycle Analyst with a configurable shunt resistance. Just tap the power wire between the battery and the controller at each end and calibrate.

I need to hook my CA like this
 

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You can do this to achieve the same result. You don't need to buy a shunt. You have less connections. You have less weight. You have less voltage drop.

Shunts in the standard 75mv (or 100mv, or 50mv) ranges are designed for dumb devices that work only with one specific range. They are not configurable, unlike the Cycle Analyst.

shunt.jpg
 
Comrade said:
You can do this to achieve the same result. You don't need to buy a shunt. You have less connections. You have less weight. You have less voltage drop.

Shunts in the standard 75mv (or 100mv, or 50mv) ranges are designed for dumb devices that work only with one specific range. They are not configurable, unlike the Cycle Analyst.

shunt.jpg

Oh very interesting....i didnt know about this way because its not in the CA manuals

There is an ohm setting on the CA display settings..i think the last screen or near the last
 
ebike11 said:
Comrade said:
You can do this to achieve the same result. You don't need to buy a shunt. You have less connections. You have less weight. You have less voltage drop.

Shunts in the standard 75mv (or 100mv, or 50mv) ranges are designed for dumb devices that work only with one specific range. They are not configurable, unlike the Cycle Analyst.

shunt.jpg

Oh very interesting....i didnt know about this way because its not in the CA manuals

There is an ohm setting on the CA display settings..i think the last screen or near the last

All you need is something else to calibrate with, either to measure the actual current or resistance. So just go buy an inline meter, or a clamp on meter for calibrating your wire/shunt. If you go the resistance route, since 1000ft of #10 is about 1 ohm for example, for testing resistance, you only need to get about 1000ft of it, measure the resistance, and divide by 1000 for an accurate milli-ohms per foot of whatever conductor your are using. If you have a really good meter than can measure small resistances accurately, maybe you can just use 500 ft. Or you can use a shunt that's already calibrated.
 
I would just measure the length of the wire accurately and that should be good enough. Certainly more accurate than other cheap calibration methods that you can come up with. Resistance of wire of a certain gauge at DC is not a mystery. Theoretical numbers put men on the moon. Theoretical figures for your gauge will be plenty accurate.

I've measured how many feet of wire are left on a big spool just by measuring resistance of a known gauge. It's a very accurate method.
 
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