MGM Low Voltage Cut Off - Owners READ
 

I have been posting my problem with my MGM 22418 in the thread http://www.rc-monster.com/forum/showthread.php?t=10124

I started this thread because I think it will get more people to comment who
have had a similar issue. My 22418 has the cutoff problem that many have reported. I am using a Flightpower Evo25 6s 5000mah 25c lipo, so my batteries shouldn't be the issue.

I know that all MGM owners don't seem to have this problem, but there seems to be plenty who do. If we can all pool our thoughts together we may be able to get it solved.

I sent the email copied below to MGM tonight


Greetings,

I am having trouble with my new MGM 22418 – 3. It seems that there are many others who are experiencing this similar issue.

My setup:

22418
Neu 1521/1Y
Flightpower EVO25 6S 5000mah 25c
HPI Savage

When I have the controller set to race mode everything works well. I don’t want to use this mode due to the loss of protection to both my Lipo and the overload protection. When I use reduce RPM mode the performance is poor, and I am pretty sure that the controller is reducing RPM even when the battery is full. When I use cut off mode the cut off is initiated anytime I go past roughly half throttle. My Lipo is a very high quality lipo with 125 amp continuous, 175 amp climb outs, 250 amp max burst capability.

I have attached a word document with screen shots from each of these settings. They were taken with the lipo fully charged and the truck being held off the ground. I also set the acceleration to 2.99, the slowest setting. Even when the truck is held off of the ground these symptoms persist.

Please notice the MAX PEAK CURRENT [A] reading for the 3 settings:

Race Mode – 260.55 [A]
Cut Off – 1679.1 [A]
Reduce RPM – 1515.05 [A]

It seems like there is something wrong with the calibration. In Race Mode the max peak current seems reasonable at 260.55 amps. In the other 2 modes the reading is over 1515 amps, which seems unrealistic.

Please let me know what I can do to remedy the situation. I have run auto tune several times and tested all of my connections. Let me know if you need any other information.

Thank you,

Shon Barrett

I have attached the screen shots from my tests. Note that I have the MGM set to the softest acceleration mode and also note the Max Peak Current differences.

It seems that my problem may be much more severe than others are having, but we all may be having the same problem. So far I feel like this is a calibration problem based on the amp draw shown while in reduce RPM mode and cut off mode. If this calibration is set wrong then why couldn't the voltage cut off be set wrong as well? They could be related.

I think that they should make the voltage cut off adjustable, or solve these issues that many of us are having. At $400 this is a considerable investment. If you have similar problems post here and send an email to MGM @ mgm@mgm-compro.cz

If they see that many of us are having this problem maybe they can adjust the software.

Cheers,

Shon

The attachment was missing a screen shot...

If the pictures don't show click on the blank area and the should appear.

Also, I check the voltage of the pack immediately after the tests and my bluepoint meter showed 24.44 volts. It is a very accurate meter. The readings at shutoff show a little over 23 volts. Just something to ponder. I know the cells start to recover immediately.

I realy hope that MGM will take care of use and take this message in consideration. I've a 16018 that i've bought from Mike at RCM who did the same thing too, and yes, for a +/- $400.00 controller it's very frustrating.
I'am sure that MGM can do something for it or Mike at RCM can place little pressure at MGM to solve this problems.

For me, i wait to buy an MMM and my MGM will stay sitting here, maybe to drop on a little 1/10 project latter.

A $400.00 controller, with 160A of capacity, and about just good to drop in a little 1/10 low amps conversion:whistle:

Hey guys, why not use this and set the controller in race mode??
For $25.00, this unit can almost solve the LVC problem of the MGM controller:neutral:

http://www.rc-monster.com/proddetail...rod=lisavercar

I have the 16024, which now runs reasonably well, after 4 motors and 3 batteries trying to sort it out. 20c batteries are the problem, 25c seems to work ok for me (still not for others). I still had to disable the quirky reverse on the thing, because I couldn't stand it. You would certainly think for a nearly $400 controller it would do all things right.

I will certainly upgrade to a MMM when they are out. I too thought about dropping this MGM in a light on road project @ 8s and keep the amps low.

That would lead me to believe that the LVC on this is too sensitive and is responding to the very brief dips in voltage during high current bursts. MGM ought to add a little delay to the LVC circuit/algorithm.

Does the MGM have an option to increase punch control? That would pull less current from the battery, which would keep the voltage from dipping to the LVC threshold as easily.

No option for the punc control, but we can adjust the time to reach 100% of the full trottle. But somes guys here had try to adjust it but not solve the problem.

I have never tested mine with the cutoff selected, so I set cutoff to on this morn and will see what mine does and I have my accel set to .012 also so it should do it if its going to...I have just reg maxamps 2s and 3s 8000mah in series...I will report back little later today when I get a chance to run it ...

same problem on 16018, at least before it cooked. it blew out the bec first, and still ran with an RX pack or UBEC, and then a couple of fets burnt out. It still runs, sort of.

I had the same cutoff problems, as well as some strange behavior from reverse/brake.

Speaking of cooking controllers yesterday I noticed that all the screws that hold the heat sinks in place on my 16018 had started to back out allowing the heat sinks to move around. Luckily I noticed before having them fall off which would not be good for the FET's.

As for the LVC problems I am convinced that if MGM just used a hard cutoff value instead of their variable calculated nonsense we would not be having these problems. The other quirky issues (low speed braking, freewheel not consistant, etc) are bad enough considering the price of these controllers.

On the upside since these problems are all programming issues there is hope that they can be resolved through software updates...preferably before feeling the need to by another controller to replace it.

It has accel setting from .13 to 3.0 sec (basically same as punch control on MM). Higher settings help, but then you have no wheely action and lame acceleration.

Even with my setting set to 2.9 I still have a problem. I think that for some batteries may be the whole issue. You need good lipos to run the types of setups we are running, I accept that. But for most I think the problem has to do with either the LVC being way too sensitive or a factory setting is off. If my batteries were breaking a sweat that would be one thing, but they are not even getting warm. My problem is so bad it does it even when the truck isn't on the ground. Under a light load such as this there is not much strain put on the batteries.

The idea of running an external lipo cutoff or a warning system is a good one, and I am looking into that, but I still think it is ridiculous that we should have to resort to that to get the performance we paid for. Plus we lose the overload protection that truly is a good feature to have.

Those who have had problems try this and let us know what happens. Set the truck to race mode with a full pack and run it for a few minutes. Does your performance increase? Log the data on the computer and compare your Max Amps and your Max RPM.

For me just holding the truck off of the ground and making this comparision I can tell a huge difference. The reduce RPM mode and especially the cutoff mode interfere and cause my performance to be mediocre. As I said on the cutoff setting it won't even go past partial throttle.

You dont have to loose the over current protection if you just set it to NiMH mode rather than race mode. That disables the internal LVC but not the over current protection. Then you could run the external LVC.

I had sucess with running mine with a slower spool timing, but I do agree it takes some of the fun out of the powerfull setup when you need to dail it down just to keep the oversensative LVC in check.

The external LVC that was linked to below works great by the way. Its no frills and no nonsense. It just works. I use it on a BK 12020 controller and its works perfectly. When the voltage dips below 3.0v/cell it just cuts off. When it comes back above 3.0v it turns back on. So when you hit your limit the truck just kinda starts to stutter a full throttle and you know your pack is about ready to dump but it still lets you drive it back in.

I actually like that solution. Could be a winner.

EDIT: One thing I just remebered... dont plug a half dead pack into that external LVC. It does seem to have a hard time sensing the number of cells in your pack if its not close to full when you plug it in. It might sense a 4s pack instead of your partially charged 5s pack. Could cause a problem if your not carefull.

NiMH mode doesn't have a cutoff? If so this could be the best solution for now.

I have never tried mt LVC on my 16018 either. I bounce back and forth between 2 4600 7-cell packs and 2 orion 4800 packs, so I just use NiMh mode. In all honesty its easy to know when to stop running a set of lipo's. Performance drops quickly and it will start to slow down. As long as you take notice in performance/speed loss, you'll know its time to pull her in. We use to do this all the time running Novak and LRP speedo's in 1/10th, pre-LVC days.

I ordered the Li-Saver, hopefully this fixes the problem. Still I would like to see a software fix for the LVC.

Anyone else using this method?

Maybe I don't understand the problem. In Lipo cutoff mode under full acceleration the esc cuts out? My 160/18 does that in reduce RPM mode not in Cutoff mode, IIRC

Thats a new one for me, but just more evidence that the current LVC system for the MGM's needs to be updated

Tne only bad part of te solution being new software is that in order to update a MGM it needs to be sent back to them. Its not like the Mamba where you can just download and install your own software update.

BashOn sorry I got that backwards. I just checked. It does not cutoff with reduce RPM but does with the hard cutoff.:oops:

It should be doable with the PC software, USBcom and cc_02 cable, there is an option in the controller software. If only they would give us the updates for download.:no:

Ya, they definitely could do it, it’s a question of them wanting to. I would require them updating the PC software to allow it.

I've just order a trusty Mamba max, anyway, i only run on 4s and the main reason why i had buy a MGM it was the fact that MM oculd not run the Neu motor but now, with the software upgrade on the MM, i'am sure that it's a way better solution than the MGM. And when the MMM will be disponible, i'll order one too.
My MGM will stay sitting on the shelve for a will, and maybe drop in a 1/10 conversion latter.

Too bad for a $$$ 300.00 contoller..

Two thumbs up MGM:whistle:

Son of a !@$#%#@!^!!!!!

Glad I got that off my chest...

I just went to take my Savage out. Setup the controller to reduce RPM, 6s Lipo (my lipo savaer won't be in for a few days) and Auto Tune. First attempt had to run home and get some pliers because the slipper was just spinning. Tightened slipper, hooked up battery, put on body and set her down. Pulled the throttle a bit and I hear a nice sizzling sound and poof, there is something coming out....

Stop the truck, pull the lid, cut the power. I plugged it back up to my laptop to see if it would connect (I have no idea why it mattered) and it did, settings were there and still correct.

My MGM is toast! I am so frustrated!! I guess I'll have to ship it off and maybe get it back by the end of summer.

It is so strange because literally nothing changed except I tightened the slipper. When it fried I was just softly starting it, not the usual throttle induced wheelie.
:bad:

That sucks BashOn sorry to hear that..... my mgm is still going, only gripes are the dang brakes engaging when I let off throttle making it flip at times on lid in street :(... I was testing the lipo on cutoff setting and mine never seemed to make batts dip below like it has with others causing studdering lvc problems etc, I am running maxamps 2s and 3s 8000mah in series and I had my accel at .012 too ....

Seems the software/firmware in the MGMs are a bit dodgy. Will check out my new build tonite and report back findings if any. *Fingers Crossed*

Would 'reduce RPM' be a temporary fix for this issue instead of using 'cut-off'?

For some the Reduce RPM setting is a solution. For me the reduce RPM setting reduced the RPMs even with a full pack. I had good punch, but little top end power. On cut off it would do just that and cut off on anything over around 1/3 throttle. Race mode seemed to give full power, though I never actually got to drive the truck in this mode. I only tested race mode while holding the truck off the ground. In race mode I got about 3000 more peak rpm versus the other modes.

Went for an initial run about 2 hours ago and got the same symptoms as you. The Motor will stop accelerating and cut out at about 1/2 throttle if i jab the throttle fast, I need to slowly accelerate for it not to cut off power. This is with using the flightpower 25C 5000mah battery so I dunt think quoality of battery packs should come into play.

seems like the cut-off algorithm is super sensitive or wrongly calibrated?

Yup, we had the same problem. Maybe MGM had a bad batch, even though we actually have different models.

I assume you were on cut off mode? Did you try reduce RPM?

Yup, on cut-off mode. Didnt try the Reduce RPM mode yet, will try it tomorrow.

I dunt know if MGM will actually do something about it, but wats the workaround to this issue? An external LVC and set the MGM to race-mode?

An external LVC and set the MGM to NiMh-mode, then you still have the over current protection

Found a nice LVC : http://www.dimensionengineering.com/CellShield.htm

Whatch out, your LVC don't work for car use:

Good catch. I guess Mike's Li-Saver is the best for our use. :)

MGM Recognizes and Solves the Problem!!!!
 

I'll save myself some typing and just paste the email I received tonight.

Dear Mr. Barret,

we tested this motor/controller/battery combination and we find this problem.
When avarage current (no peak current) go over the 105% of nominal current (current fuse start activate), can caused this mistake and controller save absurd value (and can cut off motor also).
Please, send controller back to us, we update new SW version (from Feb. 13) to controller, without this problem. This new version has one advatage also - SW is possible update via www, your PC and USBCOM+ module, no necessary send to factory for next newest version.

Best regards,
Grisa Dvorsky
----- Original Message -----
From: Shon
To: mgm@mgm-compro.cz
Sent: Tuesday, February 12, 2008 5:11 AM
Subject: 22418 LVC

Greetings,

I am having trouble with my new MGM 22418 – 3. It seems that there are many others who are experiencing this similar issue.

My setup:

22418
Neu 1521/1Y
Flightpower EVO25 6S 5000mah 25c
HPI Savage

When I have the controller set to race mode everything works well. I don’t want to use this mode due to the loss of protection to both my Lipo and the overload protection. When I use reduce RPM mode the performance is poor, and I am pretty sure that the controller is reducing RPM even when the battery is full. When I use cut off mode the cut off is initiated anytime I go past roughly half throttle. My Lipo is a very high quality lipo with 125 amp continuous, 175 amp climb outs, 250 amp max burst capability.

I have attached a word document with screen shots from each of these settings. They were taken with the lipo fully charged and the truck being held off the ground. I also set the acceleration to 2.99, the slowest setting. Even when the truck is held off of the ground these symptoms persist.

Please notice the MAX PEAK CURRENT [A] reading for the 3 settings:

Race Mode – 260.55 [A]
Cut Off – 1679.1 [A]
Reduce RPM – 1515.05 [A]

It seems like there is something wrong with the calibration. In Race Mode the max peak current seems reasonable at 260.55 amps. In the other 2 modes the reading is over 1515 amps, which seems unrealistic.

Please let me know what I can do to remedy the situation. I have run auto tune several times and tested all of my connections. Let me know if you need any other information.

Thank you,

Shon Barrett


So there it is. The new software fixes the cut off problem I have been having, probably everyone else's as well. Also after you get the update you will be able to update the software from your own computer. Its like they read this thread and raced to get this solved (I know its a fluke but still....).

Mine is on its way there.

I replied and let her know about my controller frying the other night. Hopefully they will take care of it.

Seriously I feel like celebrating!:rofl:

w00t! Sent them an email to see how I can return it to base for the software upgrade.

Typically, How long will the downtime be?

Thanks Shon!

I have no idea how long it will take, but they told me to declare a value of $15 or less on the customs form to expedite getting it through customs.

Just got a reply from them about the upgrading of my controller. Apparently once they receive the controller, it will only take a day or two to turnaround.