Newb Asks: Do we have to use regen?

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Gregski
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Newb Asks: Do we have to use regen?

Post by Gregski »

so a friend of mine asked where does the energy go if we don't have regen setup? and I want to echo his question and ask do we have to configure regen in our VCU? the Lexus GS450h in my case, I know there is an entire thread or two dedicated to that animal so I want to keep this question as generic as possible, assuming we don't care about rage, and we want to keep things as simple as possible, can we do so with an AC motor and Inverter and the extra electrons will just fall out on to the street when coasting or coming to a stop, or do we risk making black smoke
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Re: Newb Asks: Do we have to use regen?

Post by arber333 »

Gregski wrote: Fri Jun 17, 2022 3:13 am so a friend of mine asked where does the energy go if we don't have regen setup? and I want to echo his question and ask do we have to configure regen in our VCU? the Lexus GS450h in my case, I know there is an entire thread or two dedicated to that animal so I want to keep this question as generic as possible, assuming we don't care about rage, and we want to keep things as simple as possible, can we do so with an AC motor and Inverter and the extra electrons will just fall out on to the street when coasting or coming to a stop, or do we risk making black smoke
Regen comes naturally to AC motors, inverter just shifts to a different quadrant of operation for regen. BLDC motors are even easier since they have fixed magnetic flux. One could just connect a diode bridge to BLDC motor and we would have a generator. But to disconnect regen you would have to provide magnetic flux to counter magnets.

To remove regen in ACIM code openinverter you would use a BMS pin and set its value to -1.
Maybe with BLDC code it is the same effect?
You should also try using 5V pot to reduce value of second throttle manualy. I use this to reduce regen in winter so my wheels dont block...
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Re: Newb Asks: Do we have to use regen?

Post by johu »

In more general terms regen makes the car nicer to drive in inner city traffic or hilly terrain. Why heat up your friction brakes and why have to touch another pedal in the first place when you can just regenerate the energy instead?

Like arber said, regen doesn't add any hardware complexity it is purely a software feature.
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Re: Newb Asks: Do we have to use regen?

Post by remy_martian »

When you have a full battery, regen is totally non-functional. If you don't want regen, have the BMS tell the inverter the battery is full (I believe that's simply tying off to 5V on a VCU pin).

How is not having regen "keeping it as simple as possible"? You had compression braking and downshifts down hills with your ICE...now you'll be doing the soapbox derby, freewheeling, and heat soaking the brakes to where they'll completely fade and "fail" just as you come to the curve at the bottom of the hill.
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Re: Newb Asks: Do we have to use regen?

Post by Gregski »

johu wrote: Fri Jun 17, 2022 8:05 amIn more general terms regen makes the car nicer to drive in inner city traffic or hilly terrain. Why heat up your friction brakes and why have to touch another pedal in the first place when you can just regenerate the energy instead?

Like arber said, regen doesn't add any hardware complexity it is purely a software feature.
thank you and yes I get all that, and I come at this from the point of view of old school hot rodders who have no programming skills, I am trying to present a conversion that is as simple as possible, yet one you can build on and add features to, so in other words Phase 1 would be a driving vehicle without regen
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Re: Newb Asks: Do we have to use regen?

Post by mjc506 »

If you don't/won't regen, then the inverter doesn't draw power from the motor and dump it into the batteries, so the motor produces no retarding force, so the vehicle just keeps rolling unless you apply some other method of slowing down (friction brakes, rolling friction, drag, parachute, lithobraking...)

Thing is, if you have a three phase motor, you need no extra hardware to do regen, so most controllers (including OpenInverter) will have it by default. If you're instead controlling an OEM automotive controller over CAN or similar, you might be sending torque requests, so in that instance you won't regen unless you start sending negative torque requests (while moving in the positive direction).

You probably do want a little regen at least with your foot off the accelerator, and it does make sense to request more regen when you're actually braking.
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Re: Newb Asks: Do we have to use regen?

Post by Gregski »

again thank you all for your explanations, and help, I get what you are saying in terms of no additional hardware needed, and the benefits of helping the vehicle slow down using the motor as opposed to solely relying on the brakes, etc. and yes the truck will use regen in the long run, I guess what I am asking is would it cause any harm in running my truck without it, can I brake or blow up any electronic components, the inverter for instance?

again looking out for super newbs (good mechanics not so good programmers) I am trying to do a proof of concept saying hey just install Damien's VCU and off you go, it's enough to propel you down the road type of thing

forgive me for sounding so dense I honestly struggle with this concept especially since I have zero electronics background
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Re: Newb Asks: Do we have to use regen?

Post by arber333 »

That gs450h is really an ATX so it has internal clutch to disconnect power transfer. If you have no software provision for regen then i bet you would still get like 30% regen due to constant magnetics. It just wouldnt be really efficient.
If you wouldnt want that you could disengage clutch and thus brake torque transfer...
Edit: best way to test that theory would be to connect a 12V light bulb to 2 phases and rotate the motor by hand.
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Re: Newb Asks: Do we have to use regen?

Post by mjc506 »

About the only way to kill a Toyota/Lexus inverter is to disconnect the battery while moving - without the battery to dump energy to, any regen at all* will result in the bus voltage going sky high (that energy has got to go somewhere) and potentially hurting the bus capacitor and/or the IGBTs. That said, Damien's tried his best and still failed to really kill one :)

*even without requesting negative torque, it would be possible to get 'unwanted'/uncontrolled regen if the back emf from the motor is higher than the battery voltage. This can only happen well into field weakening (without field weakening, the battery can't push any more voltage into the motor) so high speeds.

So no, no harm will come to your electrics simply from a lack of regen. Test, test, test away! :)
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Re: Newb Asks: Do we have to use regen?

Post by Gregski »

alright once again I prove to be one big idiot, why, cause regen is not in any of the following Damien software versions:

gs450h_v2.ino
gs450h_v3.ino
gs450h_v4.ino
gs450h_v5.ino
gs450h_v6.ino
gs450h_v7.ino

however it does come in the gs450h_v3_user software version that is pre loaded on the VCU when you buy it

so forgot all I said, I was under the impression that I was going to have to roll my own regen code because it was a couple weeks since I looked at it in Arduino and I just forgot that the gs450h_v3_user is a special super duper release for morons like me
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