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Variable Regen

Well beyond my abilities to modify

After yesterday’s ride where I found I could visually watch my bike capturing energy as I rode downhill today I searched for how much electricity is captured by Zero motorcycles using regen. That is when I came upon this site page. Somewhere on this site or in my review for WebBikeWorld I mentioned that I hoped Zero would provide a left hand lever that would allow the rider to determine how much regen to use at any given time. Well guess what?! This genius has done that very thing on his own Zero SR back in 2015! If you click on the photo below it will take you to his YouTube video where he explains how he has accomplished this feat, which is way beyond my ability since I’m a dunce when it comes to electronics.

Clicking on the photo will take you to his YouTube video.

Here is what he has discussed on the page. I have copied it here since the actual page has MANY broken links or errors.

How to make a powerful regen lever for your Zero
« on: February 08, 2015, 03:04:39 AM »
I recently set up a custom regen lever on a Zero SR using a ZX14 clutch lever joined to a pressure transducer and wired into the footbrake function of the Zero’s Sevcon controller (see photo at the end of this post).

The result has been a very smooth and powerful regenerative brake which can push high currents of over 140A or 15kW back into the battery. The regen brake can lock the back wheel at speeds under 50kph on dry roads matching the performance of the stock rear brake with much better feel than a foot brake.

How does this compare to the regen you can get using the Zero’s Eco, Sport and Custom modes?

As you all know, the 3 performance modes each offer different levels of regen for neutral throttle and for when you first start pulling on the front brake lever (“an on/off style brake switch”). To more accurately assess the regen available in each mode you can use the amps and kWatts figures provided by the Zero phone app (or Sevcon controller software) –  see photo at the end of this post.

To give you an idea of the relative regen power, here are the stock settings for the maximum possible in Custom mode (according to the Sevcon controller). These are for a 2014 Zero SR, and they might be a little different for your year/model.

– Max battery charge rate = 40A
– Custom regen % on neutral throttle = 10% (shown as 100% in the Zero app)
– Custom regen % on (front) brake switch = 10% (shown as 100% in the Zero app)

For comparison, a separate regen lever would allow you to increase the maximum regen substantially. To achieve the power described above the following settings have been applied:
– Max battery charge rate = 150A
– Regen % on neutral throttle = 0%
– Regen % on (front) brake switch = 0%
– Regen % on footbrake = 60%
– Removed the max regen limit of 4,500rpm (which is 75% of your max motor speed of 6,000 rpm and normally means that regen doesn’t work above 120kph/75mph on SR, S and DS models).

For those looking at setting up a separate regen lever, changes need to be made in the Sevcon controller and Main Bike Board. Here are the details:
– In the MBB, the maximum regen limit should be increased (from 4500rpm) to the maximum motor rpm – usually 6000rpm.
– In the Sevcon the maximum battery charge current can be increased from 40A to 91A.
– To go higher than 91A, in the Sevcon controller the RPDO 1 setting which controls the Maximum Charge limit can be removed and in its place a dummy (16-bit) entry placed. The maximum battery charge current can now be increased beyond 91A (the MBB limit).
– In the Sevcon under Torque Control there is a braking torque limit of 72Nm. You shouldn’t need to adjust the limit as 60% (used above) of that limit is plenty of power.
– There is also a brake feathering option in the Sevcon which reduces the available regen at lower speeds (to prevent the rear wheel going into reverse). To have regen bring the bike to a foot down stop, setting the feather start to 1000rpm (about 27kph) and ending at 0rpm with an ending regen torque of 0Nm works well. A higher feather start rpm may be better if you use strong regen.
– Lastly, you need to determine whether you want the throttle or regen lever to take priority when both are pulled. I like the throttle to take priority but like most settings here there is no right or wrong, it’s what you like best for your riding.

For wet riding, lower torque settings are more appropriate and can be readily set using the three Sevcon profiles (modes) in a similar manner to what you can achieve with the Zero app in custom mode.

For road riding – this high power, well modulated brake allows you to balance front and rear brakes better and even has an in-built mechanism to safely handle rear wheel locks (not as good as ABS but keeps any wheel locks very brief). The only downside I have found with this regen setup is that on the track where you’re either on the throttle or on the brakes, it doesn’t give the motor any respite and results in higher motor temperatures. In normal street riding this wouldn’t be an issue for everything but the most spirited canyon riding.

For anyone who may be interested in adding a regen lever to their bike a friend of mine is selling the levers that offer a similar set up to mine @

Of course, you’ll still need to wire the cable from the lever into the Sevcon and make the changes in the Sevcon controller via an IXXAT CAN-USB adapter.

Based on some of the feedback for 2016 models, having a left hand regen lever would be a good aftermarket option that could be readily added to any Zero. Include a parameter in the Zero app to control its regen/braking force and I think there could be quite a few takers for this upgrade.

Interested to hear your thoughts and any questions on regen braking for your Zero.
– Is a left hand hand brake the best way to implement  regen brake?
– Is this something Zero should be considering as standard or optional for future bikes?
– What about a bidirectional throttle like in the Vectrix scooters?

I’m very pleased to have located this information. To know that in Custom Mode my bike only uses 10% regen when I’ve set it to 100% in the Zero app makes sense to me based on feel compared to my Sur Ron and the Cake Kalk&. I’m still hoping that Zero gets back to me ‘officially‘ on the actual stats on how much regen actually occurs in Sport, Eco and Custom modes.

Thanks so much to callmeburton for posting this information!

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