Help with defeating LVC on odd controller

Hi All,

As in my signature, I have a TurboAnt N1 48 volt bike. I want to defeat the LVC on the bike's controller because it's supposed to cutoff at 40v +/- 1volt, but it's shutting me off at 43.7 volts as measured with my FLUKE DMM. I have been trying to get TurboAnt to send me a new controller, but with the language barrier, and possibly their willful ignorance they have not. The battery its self has a very smart BMS and agrees that the battery still has plenty to give. Yes, the bike doesn't have nearly as much oomph at these lower voltages, and yes I know it's better not to run a battery down too low. However, at 43.7 volts the controller is being way to overprotective and there are occasional times when I need the extra range to limp home after a long ride. Normally it wouldn't matter, but sometimes I need the extra juice sitting in the battery.

The controller is odd and I cannot find reference to it anywhere. I de-potted it and removed the large capacitor so that I could see what is going on in there. Unfortunately, it's not obvious to me what parts are for sure the LVC based on what I can see so far. I have some suspicions though, and I have only de-potted half of the unit so far because it's my understanding that the LVC circuit is usually located close to the positive input directly from the batter. Below are photos (red wire is positive and green is negative):













I suspect the pair of resistors marked 2R0 or the pair marked 103 to have control over the LVC. These resistors are located near a couple transistors and the IC's which may be the voltage comparator circuit.

Any input or suggestions on figuring out how to lower or defeat the LVC would be greatly appreciated. Is there another controller that is similar to this one? I can't find anything that resembles it anywhere.

Thank you!

Also, part of my engineering firm's business is doing SMD repair on obsolete projector boards PCB's. I am very confident doing SMD rework and have all the correct tools for it including preheat bench, hot air rework, temperature monitoring...

There's a "few" threads around here about LVC mods on various controllers. Some of them have the final solution used, though most didn't even come back after intial post. This one is probably the best one, with good pics.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=23745

This is another one
https://endless-sphere.com/forums/viewtopic.php?t=85964#p1399161

a thread with some analysis and math
https://endless-sphere.com/forums/viewtopic.php?f=2&t=90019

A related thread but for HVC
https://endless-sphere.com/forums/viewtopic.php?f=2&t=23745


As a note, on most controllers, the LVC stuff is typically right next to the MCU, or very nearby, since the MCU controls everything and is what responds to the LVC; the actual level is usually programmed into it, and then tuned (or adjusted) by a voltage divider of some type, sometimes with protection (op-amp, or just passive parts) between it and the MCU (sometimes not, which is one reason why a commonly-done experiment of overvolting a controller without knowing how it's designed sometimes results in "dead" controller on first connection). Some controllers don't use the MCU to monitor the voltage with an analog input, and just use a digital pin for it, and for those it probably uses a comparator (like LM339, etc) and voltage dividers on the inputs of that.


If the linked thread isn't helpful, there *could* be info in one of these others; I haven't looked at them anytime recently so don't recall which (if any) might:
https://endless-sphere.com/forums/search.php?keywords=LVC&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

We found the lvc resistor circuit for the hksunwin title the same $14.99, I played around with it a bit like soldering in a resistor pot to change the lvc while riding, then checking the value. Search the thread.

Your battery may be sagging to the cutoff value under load, but then floating back up when you stop to measure it. If that's the case, going easier on it as it becomes depleted may squeeze out some more range.

amberwolf said:

There's a "few" threads around here about LVC mods on various controllers. Some of them have the final solution used, though most didn't even come back after intial post. This one is probably the best one, with good pics.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=23745

This is another one
https://endless-sphere.com/forums/viewtopic.php?t=85964#p1399161

a thread with some analysis and math
https://endless-sphere.com/forums/viewtopic.php?f=2&t=90019

A related thread but for HVC
https://endless-sphere.com/forums/viewtopic.php?f=2&t=23745


As a note, on most controllers, the LVC stuff is typically right next to the MCU, or very nearby, since the MCU controls everything and is what responds to the LVC; the actual level is usually programmed into it, and then tuned (or adjusted) by a voltage divider of some type, sometimes with protection (op-amp, or just passive parts) between it and the MCU (sometimes not, which is one reason why a commonly-done experiment of overvolting a controller without knowing how it's designed sometimes results in "dead" controller on first connection). Some controllers don't use the MCU to monitor the voltage with an analog input, and just use a digital pin for it, and for those it probably uses a comparator (like LM339, etc) and voltage dividers on the inputs of that.


If the linked thread isn't helpful, there *could* be info in one of these others; I haven't looked at them anytime recently so don't recall which (if any) might:
https://endless-sphere.com/forums/search.php?keywords=LVC&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

Click to expand...

Wonderful post. Thank you for the information. This will take me some time to read through and I am busy today... I may have to procrastinate on my other real work :wink:

calab said:

We found the lvc resistor circuit for the hksunwin title the same $14.99, I played around with it a bit like soldering in a resistor pot to change the lvc while riding, then checking the value. Search the thread.

Click to expand...

There is a lot in that thread. I was hoping mine would also be more obvious. I may depot the entire board so that I can see everything on it. My controller must be used in other applications as well and I would love to get the part number off the PCB.

I ASSume you meant this thread?
https://endless-sphere.com/forums/viewtopic.php?f=2&t=71128&hilit=lvc+hksunwin

Chalo said:

Your battery may be sagging to the cutoff value under load, but then floating back up when you stop to measure it. If that's the case, going easier on it as it becomes depleted may squeeze out some more range.

Click to expand...

It does. And does come back after a bit to then drive again. When the controller cuts the battery, it flashes "error 26" on the LCD over and over until the battery voltage becomes acceptable to the controller again. If I stay at PA2 which I set to about 10 MPH it will run for a bit longer several times, but the battery cannot sag below 43.5 volts or it cuts out again.

Have you tried finding a user manual for your display. Some displays have parameters for adjusting LVC up/down buy a volt or two. Even if you succeed, I doubt you will find much benefit. Maybe two extra miles of range.

In mucking around with my various batteries, and trying to run them flat to assess capacity, I only have one that actually will go down to 3V/cell I have voltage meters on the bike, or built-in to the displays to see the voltage as I ride,. Most of them are at thin ice at 3.3V/cell. I can ride gingerly on assist level 1, drawing about 90 watts, around 3amps, but anything that exceeds that will trigger enough voltage sag to trip the BMS, Out of over a dozen battery packs, I only have one that will go down to 3V/cell, but some of my others have nothing left at 3.5V/cell.

I have a battery capacity tester. Haven't done any stidies, but I casually note that under 3.4V, the machine only measures about 5-10% additional maH available on most cells. That's not much WH, if you compute it on a typical battery,

docw009 said:

Have you tried finding a user manual for your display. Some displays have parameters for adjusting LVC up/down buy a volt or two. Even if you succeed, I doubt you will find much benefit. Maybe two extra miles of range.

In mucking around with my various batteries, and trying to run them flat to assess capacity, I only have one that actually will go down to 3V/cell I have voltage meters on the bike, or built-in to the displays to see the voltage as I ride,. Most of them are at thin ice at 3.3V/cell. I can ride gingerly on assist level 1, drawing about 90 watts, around 3amps, but anything that exceeds that will trigger enough voltage sag to trip the BMS, Out of over a dozen battery packs, I only have one that will go down to 3V/cell, but some of my others have nothing left at 3.5V/cell.

I have a battery capacity tester. Haven't done any stidies, but I casually note that under 3.4V, the machine only measures about 5-10% additional maH available on most cells. That's not much WH, if you compute it on a typical battery,

Click to expand...

Yup, I've been all through the display manual and made many adjustments. LVC is not in there and I think it's simply pre-set in the controller.

When the LVC engages the first time, once it clears I can ride on PA2 at about 10 MPH for quite a while and the battery still provides a decent amount of punch for a supposed dead battery. I can even run at maximum pedal assist and with my help can go 25 MPH for a bit without engaging the LVC again. On PA2 if I am peddling, my power usage is between 15-90 watts, but at cursing speed if I help it's typically 15-25 watts.

I think this battery can add quite a few more miles if I remove the stupidity of the controller