LVC Cutoff Module - Where to buy? ... and why they are needed.

[roachslayer]

I've got a cheap chinese ESC that claims to support lipo but doesn't have LVC (naturally). I need to add a Low Voltage Cutoff module.

I looked around, I only found a couple of options, mainly sitting in the $20 range (which is more than 2x the cost of my ESC), and even then the voltage is not selectable.

Anyone know where to get an LVC module?

They seem to be rare because generally LVC is handled by the ESC (a good/proper ESC). I need this for 1/24 scale crawlers (maybe 20A max) and unfortunately quality ESCs are nearly impossible to find in small packages (because most 1/24 are RTR with lame proprietary all-in-one ESC/Rx). Hobbywing QuicRun has a 25A ESC, almost awesome, but they totally handicapped it by not providing a programmable brake (i.e. shut it the heck off, and give me instant reverse - sheesh).

I'm tempted to make a tiny, simple LVC module myself, being an electronics nerd, but would really rather spend a few dollars on something already made. Needs to support 1,2,3s options (adjustable low voltage, 3.2 - 3.7v/cell).

Seriously, if I can't find it, I'll make it... and if I make one I will make many, so let me know if interested.

 

[mikemcE]

Buy a lipo alarm ..... about $5.00


Hang up and Drive

 

[QuesoDelDiablo]

I've never seen an external cut-off but I use these low volt alarms on esc's that don't have lvc. They're loud and the the alarm voltage is adjustable.


RC Lipo Battery Low Voltage Alarm 1S-8S Buzzer Indicator Checker Tester LED | eBay

 

[JatoTheRipper]

For just a little bit more you could have gotten a decent ESC with a built in LVC. But since you have this ESC, listen to mikemcE and QuesoDelDiablo. I buy 5 to 10 of those LiPo LVAs at a time. They are cheap and, while I've never had one burn out, I do lose them. I keep one in my toolbox and one in my trailing backpack. This gives you an easy check to see which batteries are charged and which need to be charged should you forget.

 

[EeePee]

Supports a lipo? Ha. So can an ear of corn or my Honda or my tongue. Voltage is voltage, the dumb electronics don't know the difference where it comes from. The gang of us ran controllers without a LVC for years. You'll know when to stop. Lipos are like, okay I'm done, right now.

 

[roachslayer]

Supports a lipo? Ha. So can an ear of corn or my Honda or my tongue. Voltage is voltage, the dumb electronics don't know the difference where it comes from. The gang of us ran controllers without a LVC for years. You'll know when to stop. Lipos are like, okay I'm done, right now.

When a product states it supports a 2s lipo, it means 1 of 2 things: 1) can handle an input of 7.4v (well, 8.4v really), AND/OR it means 2) it is designed to PROPERLY handle the Lipo chemistry, which we all know cannot handle a drop below ~3.2v per cell. Clearly the chinese lack the latter here, and I'm not at all surprised nor did I expect to be amazed.

For just a little bit more you could have gotten a decent ESC with a built in LVC. But since you have this ESC, listen to mikemcE and QuesoDelDiablo. I buy 5 to 10 of those LiPo LVAs at a time. They are cheap and, while I've never had one burn out, I do lose them. I keep one in my toolbox and one in my trailing backpack. This gives you an easy check to see which batteries are charged and which need to be charged should you forget.

You might note from my OP above that I DID look into a better ESC, all I found was Hobbywing 1625 which has LVC, but lacks proper brake config. I'm new to micro crawlers, and admit freely I probably missed some awesome product out there, unawares. Suggestions welcomed.

As for Alarm vs Cutoff, I am determined to have cutoff. I want younger kids to play, and they are likely to keep pushing and ignoring the alarm. Furthermore, the alarms that I am familiar (with 2 buzzers and digital display) with are too BIG for a 1/24, all things considering, once the other gear is packed into place!

 

[mikemcE]

Novak made one, long discontinued. The issue is you don't want what is out there in the right price range. Im sure that a BR mini would work and has the lvc and brake.... just not under $20.


Hang up and Drive

 

[Prime]

They are cheap and, while I've never had one burn out, I do lose them. I keep one in my toolbox and one in my trailing backpack.

If there is a good spot on the chassis to attach the alarm I like to zip tie them into the vehicle that uses it. That way it is always in the car and is ready to go. "thumbsup"

 

[TacoCrawler]

I need use an external LVC alarm for my RC ESC's that don't have an internal LVC.

It was like $ 4.00 stmd on ebay.
Think my purchase was from a chinese ebay vendor.
I don't think I had to wait to long for it's arrival.

The lower cost alarms do not display voltage... but has both a loud audible and LED visual warning.
The LVC was originally checked using a voltmeter to ascertain the LVC point.
Once verified... I've never needed to check that again nor have concern.

Mine will work for both 2s and 3s LiPo's and auto determines the proper LVC.
The LVC has a predetermined cut off voltage dependent on whether a 2s or 3s LiPo is plugged in.

I generally don't adhere it to anything because I need it to be mobile
and utilize it in multiple RC's that have older non LVC ESC's.
Never had failure caused by vibration or flopping around some.
But if I did attach it to the chassis... I'd use velcro for quick removal.

If plugged into the balance plug improperly it will not become damaged, it just don't work.

Here are a few pictures of that installed on my RedCat Everest16 converted to become an 1/6 scale quad.

This is a 2s LiPo so only two green LED's light up. For a 3s use, all three green LED's will light up.
When the LVC kicks in... the opposing LED's will light up red to give visual warning.

I usually listen for the audible and unplug it asap.
That can be heard even at quite a distance.



The lower LED are not lit up and is just light reflection.
They will light up red when the LVC approaches its LVC.

One should also notice that one prong is not utilized when using 2s.











I will only upgrade the ESC to one having an LVC if the original ESC dies.

 

[roachslayer]

@TacoCrawler, nice pics, thanks for sharing your setup. But hey... you have a parasite on your quad :ror:

Again, I'm determined to have a "bolt-on" cutoff, not just alarm. It so happens I have a couple of those exact modules on their way from China. So my options are:

1. Yank the buzzer off that module and wire in a relay or MOSFET - power the rig from the relay/FET, and if LV triggers the "alarm", it kills power to the vehicle (instead of buzzing).
2. Make my own circuit.

I'm opting for #2. I've already designed the circuit. The thing is, I want it to be smart. It can't just cut off when a cell is below 3.2v, because the voltage goes up immediately when throttle is off and resting. So my circuit adds hysteresis, such that it will not turn immediately back on unless the voltage does indeed rise back up to a specified value (such as 3.8v or whatever). This is a lot like many ESCs today behave. The only difference is... I can add this to any legacy/non-lipo (or lame duck Chinese) ESC.

I'm just waiting on a couple of ICs and resistors and will have a nifty, tiny little module to add to the little 1/24 rig.

 

[Hydrocarbon92]

I've never seen an external cut-off but I use these low volt alarms on esc's that don't have lvc. They're loud and the the alarm voltage is adjustable.

I've actually been considering making one, mostly personal use for my 100A+ boat. I'm going to be offering 4WS controllers based on the Arduino microcontroller, and it wouldn't be a difficult transition.

All I'd have to do is have it read voltages at the balance plug then at LVC apply a divider (dual rates) to the signal. My 4WS controller already is coded to do the same to the rear servo, and a throttle signal [after the receiver] is functionally identical to a steering signal. I also have programming modes coded & non-volatile memory working, so I'd just have to do the voltage divider circuitry. Its resolution could be as fine as 0.013v for 3S and 0.026v for 6S. I could even implement an LCD and MicroSD datalogging if I was to go crazy.

I just have a lot of other projects to finish first...

 

[Hydrocarbon92]

Here's a really quick & dirty idea for a LVC module, use the buzzer output on a cheap warning module to activate a relay. This link below cuts the battery power on a low-amp circuit. What I'd change is connect the buzzer output wires to a relay that would break the ESC signal wire (white or orange). As long as your ESC will drop to neutral when the signal wire is pulled out of the receiver, it would work. The down side is those cheap modules don't read voltage accurately, so you'd have to test what setting cuts it at the voltage you want.

Make a Battery Protection Circuit (low Voltage Cut-off) - All

I'll look into this as a short-cut to the convoluted module I mentioned in my earlier post.