Wiring Diagram for 2WD and a Single CA V3 with remote Shunt

[teslanv]

I have come up with what I believe is the perfect way to set up a two wheel drive system and to control and monitor it with a single Cycle Analyst V3.

The attached PDF file was made with AutoCAD and individual layers can be turned on and off in the PDF, so you can isolate particular wiring runs for easier viewing.

We used this same set-up on the Fat Cargo bike we did recently, as well as another 2WD Fat Bike we built for a customer recently. Both systems have been proven a joy to ride.

http://endless-sphere.com/forums/viewtopic.php?f=6&t=70299
http://endless-sphere.com/forums/viewtopic.php?f=31&t=66184&start=125#p1048277

For motors and controllers, we used MXUS 3000W DD Hub motors for the rears, and smaller MXUS 1000W DD Hub motors for the front, and Infineon (a.k.a. Xie Chang) programmable controllers, however the motor and controller choice is not critical. Geared Hubs could be used, as could "non-programmable" controllers like the Greentime controllers and even many stock controllers that come with cheap hub motor kits, so long as they have a CA connector properly installed, and the controller for the rear motor is sized and able to output roughly 60%-70% of the total system power.



View attachment WCEC 2WD Wiring Diamgram.pdf

 

[teklektik]

Very nice presentation. The layering is a really neat feature.

However, I would not recommend tying the ebrake ground to the controllers for the same reasons that the throttle grounds are omitted. The ebrakes should pick up their ground exclusively from the CA.

This post urged me to complete a post on a simplified version of the 2WD and control wiring on my Yuba build that has been sitting in draft for a while now. An interesting feature is the single 3-speed switch that works in either 1WD or 2WD mode. The two operating modes are very workable for gear motors, but may not be the best feature for powerful DD builds like yours. Anyhow, it seemed also getting the 2WD gear motor stuff up would be good - thanks for the kick in the butt to get that finished up!

 

[teslanv]

Will regen braking work without having the ebrakes ground connected independently to each controller? It was my understanding that regen would not work through the CA alone.

 

[teklektik]

Ya - two different things. You need the ebrake signal to both the CA and controllers, but the grounds are not necessary. The controllers and CA share a single common ground reference back at the external shunt which provides a valid reference for the the throttle and ebrake signals to all three. This is just an extension of the recommended ebrake wiring in the V3 Guide for ebrakes (case 2 on page 33). That approach is the same idea is shown for the throttle wiring for external shunt hook-up in "4.2.1.4 Installation with Cycle Analyst Molded External Shunt Module (Normal Mode)" on page 18. In both cases the matching ground wire for the throttle or ebrake are omitted. The 2WD case just parallels connections in those diagrams.

These secondary grounds are in parallel with the common ground back at the shunt, but because of wiring and other resistances, heavy controller current draw can result in unwanted incidental DC current flowing through these secondary grounds along with controller motor noise. If we just omit them, everything is referenced to the common ground and works fine without the unwanted stuff occurring. The noise stays in each controller and the CA can provide a clean throttle voltage to both. In a nutshell, we want the controllers to get all their ground power needs satisfied via the main power lead instead of though secondary ground connections routed through the CA or each other.

Really liking your 2WD builds - wish I wasn't a continent away

• EDIT - I just noticed that you are running the shunt breakout cable ground to the rear controller. Missed that. This also can/should be eliminated so the hookup looks the same as you have for the front controller which is as described in the Guide. Same reasoning as above.

 

[teslanv]

Interesting. So for the speed sense wire, just the Yellow wire from the shunt BO cable needs to connect to one of the controller's CA Connectors (Yelllow/terminal 5), then.

So what is the purpose of the ground at the break-out cable of the remote shunt? Seems like it is completely unneccesary in all cases...

 

[teklektik]

Yep - you can just run the green wire to the two controllers and the yellow to the rear. Electrically, the black breakout wire isn't that useful.

It appears from 2WD threads on ES that the controller noise issue is particularly important for high powered motors. Some have noticed ratty operation, etc under high load. In these cases the grounding issues appear more important and there have been discussions about throttle isolation to minimize controller ground interactions. For low power operation the problem may not be as acute or even manifest, but doing whatever is possible to keep the controller and CA grounds from interaction seems prudent. As you can see in your own builds, the front motor runs fine with no throttle ground from the breakout cable.

If you take a look at the main wiring diagram in my thread referenced above, you can see the ground hookups inside the external shunt that go directly to the CA and controllers. The CA throttle/ebrake grounds are thus connected via the CA-DP cable to the controller Vbatt(-) connections at that single point.

At the end of the day, if you're not having problems there's no reason to change anything, but for a fresh build there's no advantage to making the connections and simply omitting them may minimize chances of issues.

 

[teslanv]

OK. I updated the Wiring Diagram above to eliminate the Ebrake Ground connection. I mixed it up a bit by adding a stand-alone speed sensor from the Break-out cable of the Remote Shunt for the purpose of eliminating the need for CA connectors on BOTH controllers. (Also found a viable use for that Ground in the BO cable of the shunt :wink: )

So there you go. It's a beautiful thing if you ask me.

 

[teklektik]

Nice.
Clever use of the wheel pickup connection

If I was going to nitpick, I would recommend removing the comments regarding %Amp limiting settings on the controllers since those are really frame/drive related and not electrical per se. 2WD design/setup has many aspects and this document is addressing electrical - not traction - details.

• For instance, I run an equal 50/50 power split without issue because of frame geometry and lower power-to-weight ratio (longer and heavier frame and reduced motor power) and also because it allows me to expect very specific power/heat/etc split between the motors for purposes of CA control. Since the controller limit settings have no effect when cruising and only affect acceleration and hill-climbing, your settings would be unnecessarily limiting for my bike with smaller motors and only 3.3kW total. I instead chose to use throttle ramping to address the issue of wheel spin. So - here we see two different strategies to address traction issues that are distinct from the wiring - your wiring would work on my bike, but your controller setting solution would be sub-optimal.

That whole power apportionment business is frankly worthy of longer discussion and IMHO a wiring document is not the place to present a single traction solution that may be inappropriate for many builds. If your document was restricted to describing your builds the detail would be accurate and useful, but for a GP wiring solution those details do not seem to belong - if you see what I mean...

Anyhow - just a thought about what is a minor part of a very spiffy document...

 

[teslanv]

The 50A Continuous/100A Max is based on the specs of the Grin remote shunt.

I have a design in mind for higher current systems as well, which would replace the Grin remote shunt with a 0.5 milliOhm external Shunt, and breaking out the CA Output cable directly to the two controllers throttle inputs and speed sensor.

At lower power levels I can see how having equal power to both wheels would be ideal. However at the power levels I have built with 2WD, invariably the rear motor produces enough torque to lift or at least lighten the front of the bike, so that were equal power applied to the front motor, it would spin out easily. The reduced power to the front motor is intended to mitigate spin-out of the front tire.

 

[teklektik]

The 50A Continuous/100A Max is based on the specs of the Grin remote shunt.

At lower power levels I can see how having equal power to both wheels would be ideal. However at the power levels I have built with 2WD, invariably the rear motor produces enough torque to lift or at least lighten the front of the bike, so that were equal power applied to the front motor, it would spin out easily. The reduced power to the front motor is intended to mitigate spin-out of the front tire.

I am referring to the specification for % power split. I fully understand your strategy - my point was that it is a specific traction solution not related to either a general traction solution or to electrical wiring. I was getting to the intent of the document as a general wiring guide vs documentation for your particular builds or builds of particular power. A matter of content not content correctness. In other words, if I was to pick up this wiring guide and use it to build a less powerful bike, the traction solution would very likely be inappropriate. Omitting that detail improves the generality - a case of less is more.

Anyhow - don't want to beat this small matter to death - just clarify the viewpoint since we seemed to be talking at cross-purposes...