MGM article on voltage under braking & lipo quality

[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

[othello]

The eagletree micropower logger does record positive amps (not negative) with an increase in battery voltage while braking.



Latest log recorded yesterday with 8s2p A123 while making speed passes. Notice the amp spikes (20-25A) while the green rpm curve is falling. I never recorded amp spikes as high as described in that article.

Basicly they say use an 8s ESC when running with 6s lipo and keep resistance as low as possible (connectors, batterys, cables ...) to minimize voltage spikes while braking.

[florianz]

good find; but honestly, what I can't understand is that these expensive esc's are not free of trouble. I have one of these cheapo-plane esc's, modded with some bigger caps. never cogged, no matter how bad the abuse is, it works.
so when I see people spending 200,- for just a controller, which burns after 2 weeks, I wonder if that stuff is worth the money...

they say, expensive must be betta!!! sure??

Myself, I don't care as I could not spend that money for the controller...

[Sammus]

Originally Posted by florianz

good find; but honestly, what I can't understand is that these expensive esc's are not free of trouble. I have one of these cheapo-plane esc's, modded with some bigger caps. never cogged, no matter how bad the abuse is, it works.
so when I see people spending 200,- for just a controller, which burns after 2 weeks, I wonder if that stuff is worth the money...

they say, expensive must be betta!!! sure??

Myself, I don't care as I could not spend that money for the controller...

hey if you cant tell the difference good for you. I tried a million different cheapo chinese air escs before buying a monster. I can't stand the motor startup algorithm used in air escs. it's optimised for a propellor driven vehicle and isn't made to stop and start like cars often do *shudders* ill never go near another air esc.

[zeropointbug]

air esc in a surface R/C = crap

[Sammus]

Originally Posted by zeropointbug

air esc in a surface R/C = crap

a more concise version of the point I was making above

[florianz]

Originally Posted by zeropointbug

air esc in a surface R/C = crap

well, I know that there is no such thing like a proper break in these things. why? dammn, the're made for planes... comments like that= crap.

thats why I will get myself a proper car esc. there are some new ones coming out right now here in germany, and when they have proven to be good, I will get one.

BUT:
the reliability and the cogging-free throttle is - at least at the one I have - just great, nothing less. So I wonder, why can't other esc's of big brands be at least the same reliable? I've payed about 40,- euro and only water was able to kill them, indestructable stuff.

That is something I can't understand, and that was the point of my post.

florian

[starscream]

I've always pushed the voltage limits of my ESC's but never had issues probably because I've always used mechanical brakes on my MT's and 1/8th scales. I've used up to 15% motor brakes, to get some front braking power, but thats about it.

[zeropointbug]

I am running 6s on the Quark (the Quark has issues with 6s), and I use only 45% brakes MAX, the EPA is set to 45%, and I usually use only 1/2 of the full 45%.

The way I brake, is usually a small amount when at speed, then I gradually depress the brakes more when it slows down, to keep the same braking action. I have never really used hard brakes ever, it's just too hard on things, drivetrain, motor (heat), and esc obviously....

[zeropointbug]

There needs to be an "at the wheel" disc brake kit for these large vehicles. Like what FG Models uses on their 1/5 scale beauties... a brake servo that depresses an oil cylinder with 4 oil brake lines going to smaller discs at each wheel. This would take all the stress away from the drivetrain, and would also give a much better braking feel.

[Nixpus]

I have a question for the pro's

In general the wireing should be as short as possible, the solder job as good as possible & the connectors should be of good quality... that much I know.

But... if I should choose between long wires from battery to ESC or from ESC to motor - which would be best? Id guess option 2 is better since the voltage drop is then on the "non battry side" of the ESC?