Can someone explain how LVC works with regen?

[EdwardNY]

I can not really find any information about how LVC works with regen.

I know that in order to use regen you need to keep the LVC close to your battery voltage. But why is this?

What is this range? Is there a optimal LVC setting?

I want to run regen on an 18s lipo setup. I am thinking about setting regen at 3.5 volts per cell of 63volts. Is this OK or may this limit how much regen I could get and I should use a different and better voltage?

This is why I need to understand how the LVC works with regen.

Thanks for anyone who can help me out here and explain this.

 

[Kirk]

What cell chemistry are you using?

 

[biohazardman]

LVC is to turn off your controller when the batteries get to low to prevent damage to them. Regen voltage should be set near your batteries fully charged voltage so it can recharge your batteries to that voltage. Many batteries will not accept much regen amperage so, regen should be matched closely to charging amperage to prevent damage to batts or controller. I constantly blew the same diodes in my GM controller some years back and later found that my batteries would not take the current of regen so the weakest link, controller diodes, would blow out.

 

[EdwardNY]

What cell chemistry are you using?

I'm using turnigy lipo 5000 mah 6s battery packs.

 

[EdwardNY]

LVC is to turn off your controller when the batteries get to low to prevent damage to them. Regen voltage should be set near your batteries fully charged voltage so it can recharge your batteries to that voltage. Many batteries will not accept much regen amperage so, regen should be matched closely to charging amperage to prevent damage to batts or controller. I constantly blew the same diodes in my GM controller some years back and later found that my batteries would not take the current of regen so the weakest link, controller diodes, would blow out.

I do not understand. There is a voltage for regen on the controller, different than the LVC? So you need to set two different voltages?

I do understand that LVC will turn off the controller, but how does it work in coordination with regen? Why could I not just set my LVC to say 42volts and have my controller work with regen at 12s, 18s, and 24s?

I honestly still do not understand how this all works.

 

[biohazardman]

LIPO operating voltages, 4.2 high side to 3.0V low, is this what you are using? edit A 42V LVC on the pack sizes you mention would shut off early on the first and damage or destroy the other two taking the cells past their low voltage limits of 3V for the LIPO batts. This is important!! Battery info here http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=19956 Lots of reading to do here on the sphere to help if you want to learn.

 

[wesnewell]

Most standard controllers are setup for sla battery voltages. And while LVC cuts off the motor, it also controls the use of regen braking. If enabled, regen braking should work with 18S lipo on a 72V controller. However if you go even to 19s, it won't work if the 19s pack is fully charged. IIRC regen started working again when the voltage dropped to ~75-78V when I was testing with a 19s pack. I've been running 24s for a while now and had to adjust LVC up to get regen working again. I set my LVC for ~88V and regen works even with a full charge of 100.8V. How you change LVC depends on the controller you have. And yes, 3.5V per cell is about perfect for rc lipo. With sag, that should keep cell voltage to ~ 3.65v per cell resting voltage.

 

[biohazardman]

My controller was older and had no regen braking option so listen to wesnewel on this one if you have something more modern.

 

[wesnewell]

There are a lot of controllers that have regen braking options. They just don't come configured with it enabled. None of mine came with it, but both had it. Just had to enable it. On one it was a simple jumper. On another it was just adding the wires.

 

[biohazardman]

I had a five year old GM regen controller. When the wires were connected it was regen when you let off of the throttle. Probly a mod to the board would have done the braking thing but it kept burning diodes and I got tired of fixing it so I just disconnected it. All my newer controllers come with it but I went with a geared motor so no longer in need cuz motors freewheel.

 

[NeilP]

I do not understand. There is a voltage for regen on the controller, different than the LVC? So you need to set two different voltages?

Yes, both regen and LVC voltages need to be set separately from with the software

I do understand that LVC will turn off the controller, but how does it work in coordination with regen?

It doesn't. It just uses the same internal components to measure them

Why could I not just set my LVC to say 42volts and have my controller work with regen at 12s, 18s, and 24s?

Set the LVC to whatever you want it won't affect the regen. that is set by the HVC setting

LVC sets (as you correctly said) the point where the controller shuts down when a certain low voltage cut off point is reached

Regen (HVC0 is the voltage that the controller is allowed to push back across the battery. With no Regen enabled, the setting is irrelevant.
So for 12s I would set the regen HVC voltage to about 50 volts. giving a cell voltage of 4.18.
You could probably go higher, and this will push more current back in to the battery and give better regen braking when the pack is fully charged...but the risk is that if you were to leave the house, with a fully charged battery, then instantly go down a very steep hill, usign regen brakign all the way, then you run the risk of overvolting the pack.

I actually have my regen voltage for a 20s pack set to 86 volts, which is effectively 4.3 volt per cell. But that does not mean that my pack get charged to 86 volts when using re gen, because it is drawing current, so the voltage is lower. Even from a fully charged pack with regen, it does not go over.

I may just know why you have got confused though. You often need to modify the controller with a resistor mod, to get it to allow regen voltages over a certain voltage..something like 60 volts. This involves changing a resistor on the board, which fools the MCU to thinking it is at a different voltage.
So since you have changed the resistor...you now hav a ratio between old resistor value and new resistor value. When you program the controller, you must use this ratio and multiply the voltage you want, by this ratio, to calculate what figure to put in the sofware.
THis is where the confusion may have arisen, since this resistor detects both LVC and HVC...so if you do the regen mod, you must alter the input LVC figure as well as the HVC figure.

 

[wesnewell]

Can't program my controllers. Once over 18s, regen doesn't work and default LVC is still ~62V. I changed the resistor value from 1200 to 800 and now LVC is at ~88V and regen works all the way to 100V. So in affect I've changed LVC via hardware. No software mods needed.

 

[NeilP]

What is the name of the resistor that needs changing Wes? can't remember..is it the R33 mod or am I thinking of a different mod?

If we can give a bname to it and the OP posts his controller type, he can search the forum for info on the mod..maybe in the Wiki already.

So if by any chance the Op is in the same boat and can not program either, then it is easy enough to do the mod, with a switch ..to have switch-able resistance for this resistor..so you can have different LVC/HVC at a flick of a switch



edit..saved the OP the trouble..it is the R12 mod


Google Advance search is your friend. use it instead of the site search..and specify the ES forum as the site to search

http://www.google.ca/advanced_search

put http://endless-sphere.com/forums/ in the site section of the search page

R12 search results

 

[wesnewell]

I know about the R12 mod, but I don't have that kind of controller. There is no resistor number on the board. See LVC Mod in first post here.
http://endless-sphere.com/forums/viewtopic.php?f=2&t=29469

 

[NeilP]

So now we wait for the OP to come back to us..

Note to EdwardNY... when you do post, try and include as much info as possible in the first post..stuff like controller make, motor/battery type ..what ever is relevant to the question. As you have probably noticed, many different controllers..so the answer is dependant on that. We are all happy to help, but make it less liek getting blood out of stone for us..give the info first, helps to get you an answer much quicker and makes it easier for us to help, and also excludes lots of helpful suggestions that are irrelevant to your particular issue.

 

[EdwardNY]

Thanks for all the responses from everybody.

I actually am in the process of ordering a controller. I was thinking about purchasing a 15fet greentime controller.

When choosing my controller options I noticed that there is a LVC setting and this setting had something to do with the regen. But now I know how this setting works with the HVC setting.

Since I needed to choose the LVC I wanted to know what was the best voltage to order the controller with.

I wanted to also know the optimal setting because I figured the LVC had some kind of effect on what later I learned was HVC.

What I am still unsure about is how the HVC works with regen? Like when you brake with regen, does it limit the voltage that is being pushed into the batteries? Or does the HVC just makes sure the voltage on the batteries does not get charged above a certain level?

What I was thinking is that in order to charge the batteries using regen, the higher the voltage the better benefit you will get with regen. So if the HVC is set too low it will not allow full voltage into the batteries.

On the other hand, HVC may just limit how much you charge the batteries. This would mean that if your batteries would never get charged more than 4.2 volts per cell, but could take a charging voltage of higher than 4.2 volts per cell.

Hope you understand what I am asking here and if anyone could comment on how exactly the regen charge voltage works.

 

[NeilP]

Now you have hiven us full information it is easier to answer.
I personally know nothing about these Greentime controllers and what board they use, so everything I have said so far MAY have been a total waste of your and my time. This is why it is important tomgive all facts when posting a question, it saves the rest of us having to drag the info out of you.

So to HVC question. Thought Inbad explained that earlier , but remember this is in relation to Infinieon based boards like Keywin, Lyen and Cell Man sell. It maybe different on Greentime boards.

HVC does not limit voltage to cells as I said earlier If you set HVC to 44 volts for a 10s pack and went down a very long hill with regen active all the way itvwould charge the whole pack to 44 volts 4.4 v per cell

HVC controls voltage sent to pack. So if you have HVC set to 40 volts and a pack that is at 41 bolts then you will get no regen braking till the pack voltage gets below the HVC

I always set mh HVC higher than pack voltage, to give regen even with fully charged battery. I charge to 4.15 per cell and regen is set to about 4.5 so 90 volts. Just have to be a bit carefull not to brake hard for the first few moments of riding.

So no idea if greentimrlev boards are Invineon based or if anyone here yet has modified them as is possible with others