Cycle Analyst PAS sensor with 72v system

chuyskywalker · Mar 7, 2021

I'm trying to make sure I've got the right understanding before I drop some cash.

I'm building up a 72v based bike and would like to add a PAS sensor. Right now, I'm happy to try out the "lower end" cadence sensor from Grin. Maybe in the future I'll consider a torque spindle, but I don't think I need that for now.

Reading up on things, however, the manual states:

PAS and torque sensors are only compatible with battery voltages lower than 52V nominal when the Cycle Analyst is providing power for the device. Connecting a PAS or torque sensor to the CA3 above 52V nominal voltage may cause damage.

From what I've gathered in other threads, I understand that the dc/dc into the CA just gets overworked pulling 72 (really, 84v) down to 10v and can cause it to fail. Pulling up the un/official guide shows that at 84, there's only 10ma and a PAS alone could potentially pull that -- no bueno.

In this other post, it's alluded that if you have a 12v system in place (I've got a 90v->12v dc/dc that can handle 26A for accessories), you can instead just power it directly, instead of from the CA.

So; should I buy the PAS above, I would need to remove the +10v pin from the connector and wire it into my 12v dc instead, right?

The device doesn't claim to accept 12v (instead 5-10v), so would I need to add another step down?

E-HP · Mar 7, 2021

Maybe I'm lucky, but I use the Grin (mini) PAS, and haven't had an issue. I'm running 20P, but I've run as high as 22P. Per the specs from King Meter, the sensor uses <10mA (<5mA idling).

http://www.king-meter.com/backend//KingMeter_upload/material/doc/2021-03-02/Mini%20Sensor%20II_User%20Manual_V1.0_20210115_1614647185669.pdf

chuyskywalker · Mar 7, 2021

E-HP said:
I'm running 20P, but I've run as high as 22P.

Do you mean 20S and 22S?

E-HP · Mar 7, 2021

chuyskywalker said:
E-HP said:

I'm running 20P, but I've run as high as 22P.

Click to expand...

Do you mean 20S and 22S?

Doh! Yup, 20S and 22S.

amberwolf · Mar 7, 2021

chuyskywalker said:
From what I've gathered in other threads, I understand that the dc/dc into the CA just gets overworked pulling 72 (really, 84v) down to 10v and can cause it to fail. Pulling up the un/official guide shows that at 84, there's only 10ma and a PAS alone could potentially pull that -- no bueno

Basically, yes.

In this other post, it's alluded that if you have a 12v system in place (I've got a 90v->12v dc/dc that can handle 26A for accessories), you can instead just power it directly, instead of from the CA.

So; should I buy the PAS above, I would need to remove the +10v pin from the connector and wire it into my 12v dc instead, right?

The device doesn't claim to accept 12v (instead 5-10v), so would I need to add another step down?

As long as the device takes 12v***, then you could just power the device from the DC-DC as have noted (by disconnecting the 10v pin first).

If it only takes 10v, then you have to downconvert that. Depending on the specific voltage drop, you may be able to just use several diodes (1n4001, etc) in series, around 0.7v drop on each one (depending on the current thru them, it may be less).

If the device will take 5v, then you can probably just run it off the CA's 5v like a throttle (which doesn't have quite the same limitations as the 10v does, though it still has only a limited current available; I don't recall how much). If not, you may be able to use the *controller's* 5v, which isn't powering a throttle, since the CA is doing that instead, depending on your wiring.

If the specific PAS sensor you're going to use is that Kingmeter one E-HP linked, then it is a 5v-only device per that PDF:

·Voltage: 4.5-5.5 V (DC)
·Quiescent current: < 5 mA
·Working current: < 10 mA

so the last option is your best one.

*** not all "12v" DC-DC's output 12v. Many are meant for automotive 12v, whcih means they output around 13.6v, up to 14.4v. So before you power anything meant for a max of 12v off of one, make sure it really is just 12.0V.

chuyskywalker · Mar 7, 2021

amberwolf said:
As long as the device takes 12v***, then you could just power the device from the DC-DC as have noted (by disconnecting the 10v pin first).

If it only takes 10v, then you have to down convert that. Depending on the specific voltage drop, you may be able to just use several diodes (1n4001, etc) in series, around 0.7v drop on each one (depending on the current thru them, it may be less).

...

If the specific PAS sensor you're going to use is that Kingmeter one E-HP linked, then it is a 5v-only device per that PDF:

·Voltage: 4.5-5.5 V (DC)
·Quiescent current: < 5 mA
·Working current: < 10 mA

Click to expand...

so the last option is your best one.

I'll email Grin and ask -- apparently they modify the one they sell to take a higher voltage so that it's inline with their torque sensor bearings, which all need 10v, apparently.

amberwolf said:
*** not all "12v" DC-DC's output 12v. Many are meant for automotive 12v, whcih means they output around 13.6v, up to 14.4v. So before you power anything meant for a max of 12v off of one, make sure it really is just 12.0V.

It's a true 12v -- comes out at 12.3v, but that's unloaded. I imagine I put some usage on it (lights, etc) it'll normalize to 12 just fine.

Santacruz · Mar 7, 2021

E-HP said:
Maybe I'm lucky, but I use the Grin (mini) PAS, and haven't had an issue. I'm running 20P, but I've run as high as 22P. Per the specs from King Meter, the sensor uses <10mA (<5mA idling).

http://www.king-meter.com/backend//KingMeter_upload/material/doc/2021-03-02/Mini%20Sensor%20II_User%20Manual_V1.0_20210115_1614647185669.pdf

I am doing the same.
I have the early CA3 (only 5v PAS) on a 52v battery with a generic Chinese PAS and have not had any trouble for some years. (Only PAS pick up needed replacing twice)
I am now running my new build at 92v (22s pack) with the later CA3 (10v PAS) and the Grin mini (24pole) PAS. So far after about a year, it is running perfect.
I am of course not powering anything else from the CA3 on either bike.

DogDipstick · Mar 8, 2021

Mine burnt after a year and in the bottom shell once winter set in. Blew up my CA.

I had every option hooked up and running though. Dial, data, buttons, ebrakes, ect. One day it just blinked out.

Grin sells a voltage regulator for this. IDK if anyone mentioned it yet. Tiny regulator.

https://ebikes.ca/miniature-5v-pas-regulator.html

E-HP · Mar 8, 2021

DogDipstick said:
Grin sells a voltage regulator for this. IDK if anyone mentioned it yet. Tiny regulator.

https://ebikes.ca/miniature-5v-pas-regulator.html

I'm not sure that would solve the issue since the input to the regulator is 10V from the CA. I think possibly the regulator allows a 5V PAS to work with with CA.

chuyskywalker · Mar 8, 2021

Santacruz said:
I am of course not powering anything else from the CA3 on either bike.

I assume you still have a few control accessories plugged in though? It looks like I'll just be on ebrakes, throttle, and 3way switch.

Haven't heard back from Grin yet, but seems like most folks find it to be working ok.

Santacruz · Mar 8, 2021

chuyskywalker said:
Santacruz said:

I am of course not powering anything else from the CA3 on either bike.

Click to expand...

Yes.
I have ebrake cut off and throttle connected.
Nothing else. (My 3 speeds are done by the three mode presets of the CA)
Power from external shunt.
My regen is separate throttle to controller (Sabvoton 96120)
Actually, this is the same settings on both my bikes.
The reason, doing it this way is that when you first switch either bike on, it starts in a (legal) mode setting.
Legal mode meaning the setting I have to be legal where I am.

chuyskywalker · Mar 10, 2021

Got the reply:

Grin Email Reply said:
All of our PAS/torque sensors are powered directly from the 10V bus on the Cycle Analyst's PAS plug which has limited current, especially at higher voltages.

It's okay to use any of our basic PAS sensor with 72V nominal batteries, but not torque sensors. If you are using a torque sensor with a 72V battery, you would want to use a DC/DC converter to step down the voltage.

So it pans out that the PAS sensors just draw so little that, even at the higher voltages, they squeeze under the line of acceptable.

E-HP · Mar 10, 2021

chuyskywalker said:
Got the reply:

Grin Email Reply said:

All of our PAS/torque sensors are powered directly from the 10V bus on the Cycle Analyst's PAS plug which has limited current, especially at higher voltages.

It's okay to use any of our basic PAS sensor with 72V nominal batteries, but not torque sensors. If you are using a torque sensor with a 72V battery, you would want to use a DC/DC converter to step down the voltage.

Click to expand...

So it pans out that the PAS sensors just draw so little that, even at the higher voltages, they squeeze under the line of acceptable.

I'm glad they replied. That's consistent with the official manual, but clears up to inconsistencies with other documentation/information that's out there.

Cycle Analyst PAS sensor with 72v system

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