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View Full Version : GP1100's and a brushless 400


ccarey75
07-16-2006, 09:48 PM
I have a brushless 400-size (Warp4 2-turn) motor in my micro RS4 and i've had a pretty interesting time of it trying to make it run properly.

motor: Warp4 2-turn BL (400 size)
esc: Mamba-25
cells: 9x GP100
pinion: 24T (largest i have so far tried) / 20T (current)

It all looks sweet but I was buggered if i could get it to run right. A friend of mine (adamc) got it going initially and it seemed to run more-or-less ok but it was a bit glitchy and tended to stutter at low-rpm. Stuttering at high (max) rpm was less pronounced but still prevalent.

Many people have kindly offered advice as to what the issue was likely to be (most pointed to either the esc or the cells being unable to supply enough current). The ESC gets pretty damn hot and very quickly so we considered overheating / overgearing might be the issue. The last possibility was a faulty receiver but by the time i got around to testing this I had my answer.

I was a little reluctant (from a sheer cost perspective) to replace either component until I was sure what the deal was so I started conducting a few tests with the equipment I had available. I'm sure there are more scientific ways of going about this but here's what I found.

All the tests below were conducted with the car stationary (wheels free spinning). Each run lasted 10 seconds (on the netball courts where we run the car is out of sight in less time than that anyway)

HEAT
- a 10 second run at max throttle puts the ESC at 60 degrees C (according to my infra-red thermometer). From what information i've been able to find online that's close to the maximum operating temp for the unit but should be safe. This test was done running the 24T pinion and the wheels spinning freely so it will probably get somewhat hotter under real load (but some air flow may compensate a bit).

VOLTAGE DROP
- measuring the voltage drop at max-rpm was a bit of a surprise. A fully charged pack hot off the charger sits at around 11.8V. At full throttle this drops to around 7.5V. I had thought the GP1100's would stand up a little better than this. It's possible that the pack is faulty but I don't know how to test this beyond measuring each cell voltage (all around 1.3V give or take 0.02V).

Either way the ESC has the cutoff set at 5V - that is it shuts down if the voltage dips below 5V. I know I can disable this setting but it seemed irrelevant if the voltage was above that anyway.

CURRENT
- All the equipment to effectively measure this seemed very expensive (ie more expensive than just buying all new components and hoping for the best). I finally settled on a kit clamp-meter from Jaycar which I'm quite happy with for $30.

This is where it got interesting for me - I had a 3S (11.1V) 1800 LiPo pack hanging around so I figured i'd use this as a comparison against the GP1100 pack.

The best measurement I could get from the GP1100 pack was around 15A. I say "the best measurement" because the stuttering caused the current to fluctuate fairly wildly making it difficult to get an accurate reading. The meter was effectively measuring a series of short bursts rather than a continuous figure.

By comparison the LiPo pack managed a steady 27A. Interestingly enough the stuttering was completely eliminated! The thing is as sooth as silk through the whole throttle range.

RPM was a fair bit higher with the LiPo (measured with one of those venom speed meter gadgets) so I assume voltage drop wasn't as extreme but I didn't get a reading on it (time was getting away from me by this stage)

CONCLUSION
I'm going to replace the battery pack and see how that goes - having had such a nice result from the LiPo I'm leaning toward just ditching the NiMH cells altogether but the chassis is nicely cut out for them so I will continue to agonise over that for a while.

There exists the possibility that the GP1100 pack is just dead and that's why it's not working properly. I've read a bunch of reports of people managing very high current draws out of these cells (and the IB1300 equivalents).

If anyone's got some advice on how I can test for this definitively I'm all ears!

-CC

alfred
07-16-2006, 10:05 PM
I really think its the cells.....there not supplying enough current or amps to the motor....try going to bigger cells.....and welcome to the boards man.....:D

ccarey75
07-16-2006, 10:32 PM
Thanks, alfred - this thread is actually a follow-up from this one posted by adamc (same car)

original thread (http://www.yourmicro.com/forums/showthread.php?s=&threadid=17885)

I originally ruled out the cells as the issue on the basis that Roleof seems to have no trouble getting high current out of them with his ESC but certainly they do seem to be MY problem for whatever reason.

Adam tried his SC1700's (sub-c) and still had a bit of a glitch happening but that was before we tried upgrading the firmware on the mamba etc. I haven't tried sub-c's since (that would be an interesting test)

Do you happen to know of a reliable test for determining whether a pack is dead? I think that's the last piece of mind I need to give up and go LiPo :)

alfred
07-16-2006, 10:34 PM
what kind of charger do you have.....you can check out the charge rate and voltage on the charger read out....cells do go bad if the load on them is just too high......and i think the motor Roelof uses is a 300bl motor.......but then again could be wrong. At what amps and mv are you charging the batts at. Usually a dead pack will hold a charge for a short time or not at all......the best way for me to test this is too run it in your model, and see how long or short the runtimes are. And as for the glitching problem what radio gear are you using....Am or Fm.....try changing out the crystal to a different freq and see if that helps.

ccarey75
07-16-2006, 10:58 PM
I have a "Swallow Advance" charger - I usually set the charge rate to 2C (2.2A - not sure about voltage but it's automatically sensed by the device i think) which I'm lead to believe is fine for those cells. They don't even get warm when charged at that current.

Runtime *was* ok a few weeks ago but i snapped one of the battery bars off in a crash and in repairing it i may have buggered a cell (runtime seems a lot shorter now so if that's a good indicator as you suggest then it would seem to fit)

glitchy symptoms pre-date damage to the pack though.

As I mentioned in the post I haven't messed around with the radio gear as yet (beyond ensuring that the antenna and signal cables are well away from the power source and the motor) since the thing doesn't glitch *at all* with a LiPo power source. (for reference, though it's a 27MHz AM radio).

alfred
07-16-2006, 11:03 PM
You should charge GP's at 1,1.5, and 2amps, you should never really go over 2 though......and i use 40mv for a 6cell pack.......you might want to try another battery pack and see where that takes you......I know lipos are expensive but you should try to get your system up and running on nimh batts first....since you now know that its the battery causing your problem, ask your buddy Adam to loan you a batt and see if that helps.

ccarey75
07-16-2006, 11:09 PM
So you reckon it's worth the investment on alternate NiMH batts? I haven't been able to find a definitive answer to "can the GP1100 supply 30A continuous"...

Perhaps the IB1300 is a better bet?

adamc
07-16-2006, 11:11 PM
Hi Alfred,

We've tried the pack from my sleeper in the car already :(

havent tried with the cp1700 pack since the firmware change though.

Chris, gimme the 9 cell pack when i see you next and i'll try it in DA's sleeper, that'll tell us if the pack is toast. gotta get a pinion for it 1st tho ;)

mount up the back end of the sleeper to your x3 and see how it goes too.

From what Chris told me about the testing between the 2 and my experiences with the car, it sounds like he's had major difference with the lipo pack in there. It came out of a heli that had similar spec / sized motor and esc combo.

Soooo, I guess the easiest way to get it going properly is to find a 3s lipo that can supply enough current (similar spec to the heli one) that will fit the sleeper chassis best.

alfred
07-16-2006, 11:12 PM
The gp's are a high current cell.....they can do 30amps but not continuously.....;) you might want to go with a couple of sub c cells.....they might just do the trick to get your ride on the road with no problems.

ccarey75
07-16-2006, 11:17 PM
I'll run a quick test tonight and see what the voltage drop on the lipo pack is under load. I'll try the SC1700 pack as well and see if it makes any difference with the current firmware. As for the current GP1100 pack I fear it may be time to sent it to Jeebers :p

Adam - IOU one 24T pinion - (unless you happen to have time to comb that entire netball court with a metal detector for the one that got thrown at 30,000 rpm (i'd start looking in adjacent suburbs)

i'll send it up with the pack sometime this week and u can have a play with it

alfred
07-16-2006, 11:20 PM
did you by any chance put a flat spot on the pinion shaft......lol.

adamc
07-16-2006, 11:26 PM
yeah :) spent about 30 mins with the dremel, it was such a nice motor i didnt want to be the one to ruin it.

adamc
07-16-2006, 11:28 PM
The car didnt have a shell at that stage so the pinion is lost to us forever :(

Hey chris, upload a couple of pics here with its pants on and off. I'm sure it will get a good reception

alfred
07-16-2006, 11:28 PM
And you might also want to put a small heatsink on the esc.....heat and electronics dont mix.....in fact they hate each other..lol....And adam why did it take you so long to put a flat spot on the shaft...lol.....And do the both of you have aim.....if not you should download it at aim.com this makes it easier and faster to talk about rc problems......

adamc
07-16-2006, 11:31 PM
my nerves arent what they used to be ;)

jk. i spent ages putting the car together, i wanted it to be the best mrs4 i'd built. It still might be.

adamc
07-16-2006, 11:33 PM
I have MSN messenger on this pc (work) but all outbound connections are blocked from here except http and https

alfred
07-16-2006, 11:39 PM
Then if your like me you need to stay away from the coffee, lol.:D

ccarey75
07-17-2006, 07:42 AM
I did some more measurements tonight with the other packs (again all tests are wheels-in-the-air). This time I extended the run times to 20 seconds - mostly so I could see what the cells did over a period of high load.

Overall the GP1100's fared ok (better than last time although I can't explain why). The SC1700's were fine and dandy (although not enough cells to be fun) and the LiPo caused a very small thermonuclear meltdown inside the ESC.

I need a higher current ESC I think... Anyone heard anything good about the bigger Mamba escs?

GP1100 x 9
- voltage fully charged (unloaded) : 12.12V
- voltage @ full throttle (20 sec) : 9.6V
- unloaded voltage after 20 sec run : 11.63V
- ESC temp after 20 sec run : 60C
- current draw @ full throttle: 20A
- est. speed (from venom meter) 85 km/h
- glitch? : not as bad as when i did the first set of measurements for some reason but still present. Only difference this time is that the pack was seperated from the car so the electronics were a good 3 inches away.

SC1700 x 6
- voltage fully charged (unloaded) : 7.74V
- voltage @ full throttle (20 sec) : 7.02V
- unloaded voltage after 20 sec run : 7.46V
- ESC temp after 20 sec run : 33C
- current draw @ full throttle: 15A
- est. speed (from venom meter) 62 km/h
- glitch? : no

3S Lipo 1800MAh
- voltage fully charged (unloaded) : 12.46V
- voltage @ full throttle (20 sec) : 11V
- unloaded voltage after 20 sec run : 12.23V
- ESC temp after 20 sec run : 98C
- current draw @ full throttle: ??A
- est. speed (from venom meter) ??km/h
- glitch? : not unless you count a meltdown


I ran into some trouble with the LiPo pack this time - because i was testing over 20 sec rather than 10 sec (like the last set). I wasn't monitoring the ESC temp during the run - just measuring it after so this last test was cut short after I smelled smoke (and the ESC insulation started visibly smouldering). It would seem that 10 seconds was about the maximum amount of time the ESC would tolerate the load from the lipo/400 combo.... Talk about finding out the hard way.

The temp reading was taken a little late too - allow for about 20 seconds cool-down (and a lot of swearing) before I had the presence of mind to point the temp gun at it.

I pulled the power immediately at that point so I didn't get a chance to do a current reading or check the RPM from the venom meter. Since the VSM is basically an RPM guage with a multiplier on it, though I calculate the measurement at around 97km/h (8km/h per volt as consistent with the other two measurements).

At that point I unplugged everything and set it aside to cool down -- fingers crossed it still works (I'm working up the courage to try it again).

soooo..... i have no idea why the 1100 pack ran nicer today since nothing else about the car has changed. I've got it on a discharge cycle as I type this to see what the cell voltages are when discharged... maybe that will tell me something?

The run with the LiPo pack was a frightening thing to behold. Smoke aside, all 4 wheels were ballooning to about 150% of their usual diameter with the high rpm and the noise was pretty amazing. I think next time I'd prefer not to be holding it in my hand - I had visions of trying to explain to a surgeon why there was a 20T pinion embedded 3 inches into my face.

alfred
07-17-2006, 06:14 PM
Glad to see that no damage was done.....How new are the Gp's by the way......did you at least cycle them 5 times before you used it.

ccarey75
07-17-2006, 07:09 PM
we never cycled the batteries - I only read about this practice a week ago actually... The cells themselves are probably the best part of a year old but they've only been used on a track (say) 5 times? (this is a testament to how little time we get to play with toys these days!)

alfred
07-17-2006, 07:49 PM
Just remember that when the batts come from cold storage like yours....you should always charge them back up and discharge them again....repeat the cycle a few more times and you will notice the battery pack will be brand new again.:D And when the you know the battery pack will not be used you should always charge them up fully.

adamc
07-17-2006, 07:50 PM
:( toasty esc. if its ok. cheapest option would be to put a mamba motor in there now.

Sounds like if we want to run the rcer motor, we'd need to put a new esc and lipo in there :(

Quark 33a ESC (http://www.quarkbrushless.com/)

Might be worth an enquiry about this little esc if the mamba is toast

alfred
07-17-2006, 07:54 PM
that esc should handle the 400 bl motor since its rated for 33amps........its suppose to be guaranteed not to cog as well.....i know some users on Half eight that have that combo....and i hear nothing but praise....must be that good.:D

ccarey75
07-17-2006, 09:54 PM
i was briefly contemplating the Mamba Max.. rated to 100A and will take a 540.

I'm a bit reluctant to give up on the Mamba purely cos I have the programming cable (and it's that cool).

pricey though - what are the quark ones worth?

alfred
07-17-2006, 09:59 PM
you can still use it....just put it in a different model.....dont know where you can find one.......but im sure other members will also help out as well.;)

Roelof
07-19-2006, 11:52 AM
22 amp with the car in the air is a lot !

Take a look at the Graupner Genius models, nice small ESC's.
But you are sure the motor is OK, not one of the coils is damaged ?

I am running a BK-Warrior 7020 on my Lehner 1020 motor and the pushed/matched GP1100 cells can handle it easy running it with 30+ amps up to 100+ km/h

ccarey75
07-31-2006, 02:57 AM
How would I check for a damaged motor coil? You're the second person to suggest that as a possibility... It does *feel* a little stiff to turn but without something to compare against it's a bit hard to tell what's normal.

I sent the (now destroyed) Mamba esc back to Castle for repair...

How did your GP1100's fare as far as voltage drop goes? At around a 20A draw mine got pounded down to less than 1V per cell on a fresh set.

alfred
07-31-2006, 06:49 AM
My only suggestion would be to send the motor in for repair.....the motor shaft should spin freely by hand....and if you say it will not do that then something in the inside of the motor has gone bad.

Roelof
07-31-2006, 10:34 AM
If you have a digital resistance meter (most digital V/A meter has it) you can meassure the resistance between 2 wires. There are 3 different meassurements possible and compare them. All 3 should be the same.

I did not meassure the voltage drop of my cells but did choose for the pushed/matched ones because they have a higher voltage and a lower resistance so a lower voltage drop an a high rating current

ccarey
08-01-2006, 07:03 AM
Just tried measuring resistance... i don't know if it's my meter but i found it difficult to get a reading. Looked like all 3 combinations of 2 wires had around 0.1 ohms resistance (i say "looked like" as the measurement would drop off to zero after a couple of seconds)

I took a quick look online and that figure seems to be about right

(link) (http://www.aircraft-world.com/prod_datasheets/rcer/bl4-15.htm)

Sounds like i just need a beefier ESC to make this thing work. I might get the Mamba repaired and sell it I think.

alfred
08-01-2006, 11:51 AM
Have you looked at the Quark ESC......I hear nothing but good things about it.:D

ccarey75
08-01-2006, 06:19 PM
hehe - look like i already had a login here... my brain is going to mush

I looked at the Quark - the only thing that gives me pause is that i haven't seen anyone running anything really hot off it.

Roleof's BK Warrior thing seems to be pretty effective... shame they're so pricey! Better start saving :)

Silver Supra
08-01-2006, 10:04 PM
Friends over at XMODRC/Atomicmods all say the Quark 33 is perfect for the really hot BL motors. Outperforms the Mamba by a long shot. Definately worth the extra dough from the Mamba 25.

Roelof
08-02-2006, 12:12 AM
The BK Warrior is a very good ESC but it is to large to fit nicely.

Take a look to the Graupner Genious series, they have a nice size and people have good experiences with them.