Regen Advice please.

[Gow864]

I have a Lyen 184110 controller. It has the "R12" mod. I'm running 24s life 87.6 fully charged. What should I set the regen level to? there are three options 55V,60V,75V any help on this would be great.

Gow.

[mvly]

If Lyen told you to set your Shunt to 1 miliOhms, then set it to 75V and you should be able to regen with 24s. Just make sure you set Regen Power to the lowest because it can really damage the FETs if you set it to anything higher than that. If you don't know what I am talking about, it's best to not set it and double check with Lyen for more help.

[John in CR]

If Lyen told you to set your Shunt to 1 miliOhms, then set it to 75V and you should be able to regen with 24s. Just make sure you set Regen Power to the lowest because it can really damage the FETs if you set it to anything higher than that. If you don't know what I am talking about, it's best to not set it and double check with Lyen for more help.

Why would it damage fets? The regen current limit is pretty low, and always lower than our forward current limits. Sure start with low, because a light regen is great for keeping speed under control going down hills without heating up and wasting your mechanical brakes. In flat land riding, gentle regen takes more getting accustomed to when you engage. The force of regen varies significantly by motor with speed winds having less force.

I have 2 ends of the spectrum in my regen settings. My cargo bike has extremely soft regen with it set on high, so soft that I modded the shunt just to increase regen force. On my SuperV, the controller has 12 shunt wires and the shunt resistance is so low that even with regen set to Low, I get over 70A of regen current, and when you hit the brake you better be ready, because it has very strong braking force.

It's your batteries that need to be able to handle regen. OTOH, if you're already running your controller near it's limits, then regen is work, so it's a good idea to get a feel for how stressed your controller before activating regen by seeing how hot it gets. Then compare that to how hot it gets using regen.

Also, I don't know if Lyen fixed his programmer, but regen has low. medium, and high. It's not Off/Low/High like the programming version I got from him has.

If you don't do much moderate throttle cruising, and regen force is mild with your motor, then I'd also suggest trying throttle activated regen. That's what I have on my cargo bike, and everyone who's tried it loves it. There's something appealing about the simplicity of twist to go, and let off to slow down. It is problematic trying to cruise at about 1/3rd speed though with the regen sporadically going off and on. OTOH I've gone entire rides without touching my brakes and there's something liberating in that simplicity.

John

[Jeremy Harris]

Why would it damage fets?

A fully charged 24S pack will be slightly over 100 V, so if you regen on a full pack there's a risk that the voltage will go over the max of 100 V for the FETs. Add in the inevitable supply ripple and spikes, and the risk of blowing 100 V FETs increases quite significantly

[John in CR]

It's not lipo, it's LiFePo4 and 87V fresh off the charger in the OP, so he'd have to start down a pretty big hill with a fresh charge to run into a voltage issue.

Am I correct in my understanding, that the fets don't really care which direction the current is flowing, since they're essentially a switch. Maybe the non-matching hi/low count controllers like 9 or 15fets might care if the roles hi/low are reversed during regen, but otherwise he should be fine, shouldn't he?

Why would it damage fets?

A fully charged 24S pack will be slightly over 100 V, so if you regen on a full pack there's a risk that the voltage will go over the max of 100 V for the FETs. Add in the inevitable supply ripple and spikes, and the risk of blowing 100 V FETs increases quite significantly

[Gow864]

Thanks for the replies guys, but i'm still confused. Ed Lyen has told me to multiply the regen voltage by 1.33 to get the actual regen voltage. So, if I program the regen voltage to 60V (60*1.33=79.8V) does that mean that it will regen to 79.8V or above 79.8V. what happens if it program it to 75V (75*1.33=99.7V)

Thanks again,
Gow.