MGM article on voltage under braking & lipo quality

Good article, at least for me. See attachment.

[BrianG]

Good find! The results make sense and reflects what I have found in some personal tests. The solution to use an ESC with at least 1s-2s higher rating than the voltage used is something that I currently do, and has worked well. Actually, it is a good practive with anything electronic for greater lifespan.

But I guess it depends on the manufacturer too; do they rate their ESC voltage/current close to the max component rating to increase sales, or do they rate their ESCs with some "headroom" already built in? I would assume that the more expensive ESCs fall into the latter category, while cheaper ESCs fall in the former category.

Option b, using a controlled shunt device, is what the MMM uses. However, this is not a perfect solution because if they are overworked and fail (fail open), the user most likely will never know since its presence isn't obvious during operation.

[Nixpus]

Super informative! Much appreciated

"sneaks off to order better connectors and shorten his cables".

Now that we are at it... where do you get super connecotrs at a reasonable price?

Originally Posted by Nixpus

Super informative! Much appreciated

"sneaks off to order better connectors and shorten his cables".

Now that we are at it... where do you get super connecotrs at a reasonable price?

They even say I shouldn't use Deans!

Well, what now? Those super-connectors got super-prices...

What I don't understand is that at the bottom of page 5 they recommend 6s2p packs to lower the inner resistance.

I just looked up the inner resistance of the hyperion g3 35c packs:
3s4200: 4milliohm
6s2200: 14milliohm

Wouldn't two 3s packs in series have a lower resistance than two 6s packs in parallel(6s2p)?

[BrianG]

Actually, they wouldn't. Two 3s4200 packs in series yields 8 mohm (4 mohm + 4 mohm), while two 6s2200 packs in parallel yields 7 mohm (14 mohm || 14 mohm).

[crazyjr]

If i am reading that right, Then you should figure 1/3 over the working voltage you plan to run. I did see something similar in my eagletree runs, not in voltage but in amps. One or two runs showed 200+amp spikes where it was braking, this was on a 9XL fegaio. I thought it was a glitch and deleted it, wish i had kept it to show, those runs were showing 120 to 140 amp spikes on acceleration on a V2 micro eagletree. I never seen those spikes witth my Neu though, Is it possible that the quality of the motor has an effect?

[BrianG]

Maybe, but I would tend to think that the Neu is more efficient so less power is needed for the same performance? Also, Neus, being 4 pole slotted, has more torque.

Weird though that a manufacturer is saying you can't use their esc's at the max rated voltage if you're running motor brakes. Have there been any problems with mgm esc's that anyone knows of?

[zeropointbug]

Well, before I got these G3 35C 4200 packs, I have been using a 7s1p, and 7s2p A123 packs in my revo running a 1512/3D/F on a Quark.... and when I modified the Quark last week I noticed that the internal caps leads were blown/melted right off the board! Only the externally soldered on caps were doing something!

After I did the cap bank mod, I for surely found the brakes to be different, the motor sounded different under braking (think the buzzing noise).

So now with this Quark mod, and some very low resistance packs (G3/35C), it should be golden now.

I never actually looked at the whole article, were they talking about ESC destruction and/or battery damage? I am assuming the former.


BrianG, I am wondering if I should make another larger cap bank on the Quark in a reciever box (asthetics) with the 'no-spark mod? It can't hurt right, lower the system resistance further, can only be good for everything I would think.

[crazyjr]

Originally Posted by drkdgglr

Weird though that a manufacturer is saying you can't use their esc's at the max rated voltage if you're running motor brakes. Have there been any problems with mgm esc's that anyone knows of?

It's possible that this is a recent discovery, or one that was known but not proven till recently. Like i said i thought mine was a glitch

BrianG, I forgot i also switched to a quark esc as well. Is it possible that the quark has the same gate like thing as the castle monster?

[zeropointbug]

Originally Posted by drkdgglr

Weird though that a manufacturer is saying you can't use their esc's at the max rated voltage if you're running motor brakes. Have there been any problems with mgm esc's that anyone knows of?

MGM seems to be weird that way... they sell you a overpriced product, and then they make articles and disclaimers about their product.

[zeropointbug]

crazyjr, I believe the eagletree doesn't read/record negative currents, I think it must have been either a glitch or just a current peak.

[BrianG]

Originally Posted by zeropointbug

...BrianG, I am wondering if I should make another larger cap bank on the Quark in a reciever box (asthetics) with the 'no-spark mod? It can't hurt right, lower the system resistance further, can only be good for everything I would think.

Electrically, I'm sure any bit helps. But realistically, you run into placement/mounting issues. Also, if the caps are soldered somehow to the ESC, the weight of bus bars and the caps themselves would place considerable stress on the PCB. And, at some point, you get very little return for the work/expense. If you already have twenty 500uF caps (10,000uF), adding 4 more to get 12,000uF isn't helping a whole heck of a lot.

Originally Posted by crazyjr

...BrianG, I forgot i also switched to a quark esc as well. Is it possible that the quark has the same gate like thing as the castle monster?

I'm not sure, but I don't remember seeing a TVS device on the Quark. Of course, I never looked specifically. The ones I've seen are roughly the size and shape of a typical FET that you'd find on an ESC (square/rectangular and flat), and it has two leads.

Originally Posted by zeropointbug

crazyjr, I believe the eagletree doesn't read/record negative currents, I think it must have been either a glitch or just a current peak.

It might not record currents below zero (has anyone even tried setting the graph low point to a negative number?), but there should be a voltage peak that may be at or above the battery voltage.

[zeropointbug]

I've got 6 caps on the Quark as it is, mounted very sturdily and safely. I was thinking about putting 10 cap bank in a receiver box wired up to the Quark with short wires. But, like you said, probably not necessary... as 2 caps has held up this long, and the 6 cap bank made such a difference.

http://www.rc-monster.com/forum/show...uark+regenesis