Anybody have the I/O spec for CA-DP Cycle Analyst

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Hello,

ebikes.ca has the info listed in an image on their site:

http://www.ebikes.ca/drainbrain/CA_taps_20A.jpg

Good luck,

Paul.

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no the Vbat is just like the description says. it is the total voltage of the battery. it is not scaled in any way.

Isense is the voltage across the 0.001ohm current sense resistor built into the larger controllers. the smaller controllers use a 0.0019ohm value. the voltage would range from 0 the the max determined by the current limit. for the 40A controller using a 0.001ohm shunt that would be 0.04V and on the smaller 20A controller it would be 0.038V

rick

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Hi Wayne, the accuracy of the resistive shunt current sensing is quite good in most EV applications. However, in cases where it is used with a power supply that has large switching noise then this seems to get coupled to the output in the form of a DC offset, so if the CA is used for instance for monitoring a small charge current going into the battery pack from a cheap charger, then the amp-hour accumulation isn't always that accurate. I haven't tested it yet but I've been wanting to see if simply using a shielded twisted pair lead for the the current sense leads solves this or not.

The actual input range for the differential sense leads across the shunt is +- 220mV, and the common mode can't exceed about 400mV from ground (low side current sensing only). The speedometer signal has an internal pull-up to 5V as well as a diode on the lead, so you can use it either with a magnetic reed switch, or a toggling signal that is 0-5V, 0-12V, or even 0-100V if you felt like it.

Justin

wrobinson0413 said:

Thanks Rick for the info. Sounds pretty straight forward to hook up. I wonder how accurate the Cycle analyst can be using the raw current sense like that. I have had experience with some high performance servo controllers that use resistive shunts, and their current sense is fairly sensitive to the length of the differential pair coming off the shunts. The amount of noise that can be coupled into the lines gets larger the further away you get away from the shunts, especially with the bridge running. I suppose I will just have to try it out.

Cheers
Wayne

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Hi Wayne, in the analog Crystalyte controllers the main capacitors are on the mosfet side of the shunt, whereas on most other controllers that I've opened up the capacitor is on the battery bus, before the shunt. For pulse-by-pulse current limiting it needs to be wired up in the latter manner. As far as the CycleAnalyst goes, it doesn't matter one way or another, since the low voltage signal across the shunt is filtered to remove PWM noise (RC ~ 2mS) anyways before the amplifier stage.

Justin

wrobinson0413 said:

Since I have not taken apart any ebike controllers recently, maybe you can tell me if they are placing the shunts behind the caps, ie. between the mosfet source pins and the negative side of the caps, or whether they are placed after between the negative lead and capacitor/source pins. I realize that this is a little off topic, but it would help me understand what portions of the current that the Cycle Analyst actually it looking at when hooked up to a controller instead of the standard method with the external shunt looking at battery current.

Thanks
Wayne

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wrobinson0413 said:

Hi Justin

Just a couple of more questions regarding the current sense. So with the digital controllers, they are using the standard brushless DC bridge configuration with sense resistors.

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Well, just one sense resistor that is shared by all 3 half bridges.

From your description of the pulse by pulse current limiting, I would gather that these controllers are not close loop current controlled, but rather controlled by peak current limiting .

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No, the controllers generally have average current limiting, (so the battery rather than the armature current). Surprisingly few have actual peak current limiting.

Is this being used to give feed back on the motor current only or is it being used to infer the battery current.

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Average current across shunt equals the battery current.

But, maybe I am not understanding the function of the Cycle Analyst. Is it not just a monitoring system to datalog and display battery stats, with a shutdown feature for when the battery is discharged

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Correct, it is mostly a display/monitoring system, but it does have a single 0-5V analog output line that can be used to regulate a controller (usually via the throttle signal) in order to scale back the controller power when current, speed, or low voltage limits are exceeded.

Justin

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wrobinson0413 said:

One other detail that you might know is what sort of switching scheme is being used by the BLDC ebike controllers. Are they using complementary magnitude with center aligned or edge aligned PWM?

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Neither generally. The techniques you are referring to apply when you have all three (or at least 2) phases doing PWM, as required for sinusoidal drive waveforms. While there are sinusoidal BLDC setups, pretty much every single ebike controller uses a trapezoidal drive, where one phase is held tied to a bus, another phase does PWM, and the 3rd phase is in a high impedance state.

By the way, did you start you trip off ok? I hope that you have your rain gear, because Ontario has been seeing record rain falls. Maybe we will have some dryer weather for you when you pass through(^^).

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I am off, midway through BC now, and am hoping you can fix the weather over there in ON before I arrive OK

Justin

justin_le said:

wrobinson0413 said:

One other detail that you might know is what sort of switching scheme is being used by the BLDC ebike controllers. Are they using complementary magnitude with center aligned or edge aligned PWM?

Click to expand...

Neither generally. The techniques you are referring to apply when you have all three (or at least 2) phases doing PWM, as required for sinusoidal drive waveforms. While there are sinusoidal BLDC setups, pretty much every single ebike controller uses a trapezoidal drive, where one phase is held tied to a bus, another phase does PWM, and the 3rd phase is in a high impedance state.
Justin

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This is what I thought most ebike controllers did for their switching scheme. I do wonder though if the new regen controllers like golden motor's use a more advanced method? Maybe you know, Justin, since you seem very knowledgeable both about ebike controllers and PWM technical stuff.

BTW, what does your own new bike controller use for it's switching scheme, Justin? I'm sure it must be something better than the standard ebike controllers, specially if you pack so much power into such a small box! Maybe it uses the more advanced scheme Wayne suggested, using offset complementary switching of the phases or some such thing? And faster switching times, I'm sure. You can also keep your secrets if you wish, Justin, I don't mean to pry...

My last controller ended up using center-mode PWM, using complementary duty cycles on the switched phases (as Wayne was suggesting), which I found worked great.

BTW, good luck on your trip, Justin - You are an inspiration to me for sure! Techs that travel off the beaten path are not too common (non-existant?) where I live! I hope to cross your path when you hit the east coast...

Patrick

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justin_le said:

Neither generally. The techniques you are referring to apply when you have all three (or at least 2) phases doing PWM, as required for sinusoidal drive waveforms. While there are sinusoidal BLDC setups, pretty much every single ebike controller uses a trapezoidal drive, where one phase is held tied to a bus, another phase does PWM, and the 3rd phase is in a high impedance state.

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This is what I thought most ebike controllers did for their switching scheme. I do wonder though if the new regen controllers like golden motor's use a more advanced method? Maybe you know, Justin, since you seem very knowledgeable both about ebike controllers and PWM technical stuff.

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The only brushless ebike controller I have seen that wasn't a standard 3 phase 6-step BLDC trapezoidal drive scheme is the TidalForce, and that was quite a different beast unto itself for many reasons.

BTW, what does your own new bike controller use for it's switching scheme, Justin? I'm sure it must be something better than the standard ebike controllers, specially if you pack so much power into such a small box! Maybe it uses the more advanced scheme Wayne suggested, using offset complementary switching of the phases or some such thing?

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No to all of the above, actually. The only thing you would notice if you went to a sinusoidal drive on an ebike hub motor is slightly less power. There really isn't any benefit to that scheme unless you are powering a precision servo motor in an application that requires minimal torque ripple. In that case you also use a motor that is wound to produce a sinusoidal back-emf waveform. I haven't seen any hub motors that are sinusoidally wound.

And a center-aligned PWM mode means that you have at least two channels doing PWM, which means twice the switching losses as the conventional 6-step drive technique where there is only one phase at any given time that is switching.

Part of the reason Crystalyte and other ebike controllers are unnecessarily large is because they don't do any motor current limiting. So the '20 amp' Crystalyte controller when powering a low resistance motor from a stall might have 50-60 amps flowing through the mosfets and the motor leads, and so this is what they needs to be designed to handle without frying. If they independently regulated the motor current as well as the battery current, then these smaller controllers could easily be made into 30 or 40 amp motor controllers without risk of blowing up.

BTW, good luck on your trip, Justin - You are an inspiration to me for sure! Techs that travel off the beaten path are not too common (non-existant?) where I live! I hope to cross your path when you hit the east coast...
Patrick

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Me too! I'm still a ways from getting to that part of Canada but we'll stay in touch.

Justin

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Does anyone know the specifications of the resettable polyfuse for the + connector to the cycle analyst?

Thanks!

Johnbear said:

Does anyone know the specifications of the resettable polyfuse for the + connector to the cycle analyst?

Thanks!

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Hi John, it only needs to handle 10mA, but up to the blocking voltage of your battery pack. The ones I've been using are surplus 1.3Amp 60V units. You could use a regular fuse too, or none at all. It's only there in case you accidentally short out the battery pack via the V+ and Gnd leads to the CA unit, say either while probing around with metal tools or in the event of an accident that cuts and severs the CA leads, shorting them together in the process.

Justin