MMP Start Power

[Lauri]

I just ran first time the MMP with 1/10 touring stock 17.5. Have ran it before with 1/8 buggy. Everything worked nice. MMP with CHEAT was many tenths faster than the regular ESCs - very very nice. I think there will be many MMPs in the stock class after yesterday's race ;)

But my question for you is about the Start Power setting (low, medium, high). I searched the forum but didn't find an answer. Can you give me the "boring technical" explanaition about it? What does it actually change? How does it affect the performance? Lets say I have top notch battery, should I go with medium or high? Or how would I know if I can use high setting?

I tried all three settings. With "high" setting it did "kill the battery" after 3 minutes of 17.5T touring car running (just like warned). Brought the battery performance/voltage down. The same battery works very well with 5.5T modified touring car with Novak GTB.

Would it help if I run additional caps to save the battery and still use "medium" or "high" Start Power setting? MMP has very low capacity internal caps. Would few external 2700uF or 4700uF caps "help" the battery when running "medium" or "high" Start Power?

[BrianG]

This should do it: http://www.rc-monster.com/forum/show...06&postcount=3

[Lauri]

Thanks Brian, but I think there's more to it. I'm running sensored + CHEAT Touring Car 1:10 scale 5-minute runs. The car only _STARTS_ one time. I'd like to know better how and when the Start Power works.

It is also weird that 17.5T motor with "high" Start Power setting kills the battery but running 5.5T motor with regular touring car ESC works nice. 17.5T kills the battery voltage wise but only uses 1500mAh out of 4500mAh. 5.5T uses 3000mAh out of the same battery. I'm guessing the "killing" by "high" Start Power setting is done by the pulsing current that LiPo can't handle. I'd like to know if additional fast low impedence caps would help in this situation?

At the moment it is a mystery setting for me. I'd like to know more about it or if Patrick doesn't want to go too much into details just let us know when to use which setting. And when not to use.

I tought I had good enough LiPo and use low-power 17.5T 540-size motor ... but "high" setting was still too much.

Start Power --

Start power is the maximum amount of power that the STARTUP algorithm is allowed to apply to the motor PRIOR to detecting that the motor has started (or the position of the rotor.) The higher the start power, usually the quicker the startup algorithm can successfully start the motor, but the more power might be wasted (read "extra motor heat") in starting the motor.

Remember, these are sensorless motors and controllers- - prior to startup the controller doesn't know the position of the rotor, and must "tickle" the rotor to detect rotation and position of the rotor. The higher the power in the "tickle" the quicker rotor position can be detected.

[jhautz]

Its the cheat mode that probably killing your battery. You are advancing the timing on the motor with the cheat mode. That takes more juice and creates more motor heat. If you are burning through more with the MMP and CHEAT mode vs another conventional esc then try turning the cheat mode off on the MMP. That should get you back to the same run time (and speed) of the other esc. If you are close on run time you will need to balance the extra power with the amount of juice you are burning. Maybe you can find some middle ground with a milder cheat mode setting that will still get you little extra sped but not burn up too much more power.

Cheat mode will also draw a higher load on your battery becasue of the advanced timing so that would also explain the lower voltage you are seeing.

[BrianG]

There probably is more to it since that explanation was for sensorless operation. I think one of the Castle Guys are gonna have to explain how Start Power applies to sensored operation. And when they do, I can update that post.

[Lauri]

jhautz, you're guessing wrong. I have no problems with using CHEAT mode. I know what I'm doing and I've tried different settings. Everything is OK except I don't understand the Start Power setting. Please note that in the first post I compared 17.5T with MMP to 5.5T with Novak GTB - the latter one is about 3x overall power and battery holds nice. I have no problems with overall power, CHEAT or using too much timing. 17.5T 540-size motor is low power compared to what the ESC or my LiPo can cope with.

I just want to know more about the Start Power. When to use "medium" or "high" settings. And if Castle guys can tell us - what does it change and when exactly it makes a difference and how. What's the trick behind the Start Power ;) ?

I have stock 1/10 touring race coming up and don't have enough track-time to test different settings so I'm asking. Gotta get the gearing and CHEAT mode settings right with 3-4 runs. Not enough time to start testing the Start Power magic :)

[Pdelcast]

Originally Posted by Lauri

jhautz, you're guessing wrong. I have no problems with using CHEAT mode. I know what I'm doing and I've tried different settings. Everything is OK except I don't understand the Start Power setting. Please note that in the first post I compared 17.5T with MMP to 5.5T with Novak GTB - the latter one is about 3x overall power and battery holds nice. I have no problems with overall power, CHEAT or using too much timing. 17.5T 540-size motor is low power compared to what the ESC or my LiPo can cope with.

I just want to know more about the Start Power. When to use "medium" or "high" settings. And if Castle guys can tell us - what does it change and when exactly it makes a difference and how. What's the trick behind the Start Power ;) ?

I have stock 1/10 touring race coming up and don't have enough track-time to test different settings so I'm asking. Gotta get the gearing and CHEAT mode settings right with 3-4 runs. Not enough time to start testing the Start Power magic :)

In sensored mode, start power limits the amount of current allowed at startup -- startup is the first few times the motor turns. This allows the motor to develop some EMF before the throttle is allowed to ramp up quickly.

If you use a little throttle at the start, you probably won't notice any difference.

Where it really makes a difference is in drag racing -- high start power will allow a faster spool-up of the motor. BUT -- it's dangerous as it is more likely to damage a motor.

That help?

Patrick

[Lauri]

Well... I thought it affects things more.

I raced 1/10 touring 17.5T. With "easy" setting everything was ok and lap times consistant. It was a club-race day so every run was 5 minutes + 1 lap. Then I tried "hard" setting. 2 runs I noticed that lap times dropped after 3 minutes and few last laps were a lot slower. I just didn't get the speed ot of the car. You could visually see that acceleration on the main straight was slower.

You would think that maybe motor over heated or battery was empty but no. Motor was OK (70 Celsius max), ESC was cool, battery was cool. And still 2 runs and both runs the car just didn't have the kick after 3 minutes.

I think the battery died (didn't have the voltage!) for some reason and it was caused by the "HARD" Start Power. After charging the battery only 1500mAh went into 4500mAh. So battery was... dead by the voltage, not drained. I've ran the same battery with 1:10 modified 5.5T with great success and no problems before.

As I'm racing onroad I only ONCE start from standstill and then run-run-run consistently 11.4-12.0 laps for 5 minutes.

Do you think Start Power can affect in this case? I can't think of any other reason. After going back to "easy" I didn't get the problem any more. So it has to be Start Power or... or some mysterious other thing nobody could think of.

I'm guessing it has something to do with the pulsing current that LiPo can't handle. I would like to know if Start Power maybe somehow changes this? Would extra caps help? Or if the Start Power only affects the FIRST start then I could just leave it "easy" and that's it?

[Pdelcast]

Originally Posted by Lauri

Well... I thought it affects things more.

I raced 1/10 touring 17.5T. With "easy" setting everything was ok and lap times consistant. It was a club-race day so every run was 5 minutes + 1 lap. Then I tried "hard" setting. 2 runs I noticed that lap times dropped after 3 minutes and few last laps were a lot slower. I just didn't get the speed ot of the car. You could visually see that acceleration on the main straight was slower.

You would think that maybe motor over heated or battery was empty but no. Motor was OK (70 Celsius max), ESC was cool, battery was cool. And still 2 runs and both runs the car just didn't have the kick after 3 minutes.

I think the battery died (didn't have the voltage!) for some reason and it was caused by the "HARD" Start Power. After charging the battery only 1500mAh went into 4500mAh. So battery was... dead by the voltage, not drained. I've ran the same battery with 1:10 modified 5.5T with great success and no problems before.

As I'm racing onroad I only ONCE start from standstill and then run-run-run consistently 11.4-12.0 laps for 5 minutes.

Do you think Start Power can affect in this case? I can't think of any other reason. After going back to "easy" I didn't get the problem any more. So it has to be Start Power or... or some mysterious other thing nobody could think of.

I'm guessing it has something to do with the pulsing current that LiPo can't handle. I would like to know if Start Power maybe somehow changes this? Would extra caps help? Or if the Start Power only affects the FIRST start then I could just leave it "easy" and that's it?

It's hard to say -- there are so many variables. It's possible that you just had a bad battery.

Start power ONLY affects startup of the motor -- it doesn't do anything else after the motor is running.

[What's_nitro?]

Forgive me if I've missed it in your post somewhere, but which battery are you using? At 4500mAh even a 15C continuous battery should not have any trouble handling the burst current in a 1/10 TC. How many cycles are on the pack? Have you cycled it on the charger lately to see what usable capacity is left in it? If it's an older pack it might be at the end of it's usable life.

Adding caps might help you get a couple more good laps but if the battery is bad that's only a short-term fix.

[Lauri]

Guys, the battery is good ;) It isn't new but I've just a week ago ran it with 5.5T modified TC and no problems like that. 5.5T on the same car uses 3000mAh from it and 17.5T on the same car uses only 1500mAh from it. It is 4800mAh and 4500mAh is the real capacity (4.2V to 3.5V @ 5A discharge).

Ok. I will then try to figure out what was the case. Patrick, could you only state some RPM range the Start Power is active? For an example up to 0 to 1000rpm?

Maybe it has something to do with the capacitors. With 5.5T I run Novak GTB and have external low imp caps (4x2200uF 16V). With MMP I didn't use external caps and MMP has very small internal ones. Maybe the LiPo didn't handle the pulses (you all know the theory).

We'll see in a weeks time...

Usually I am few tenths slower than our fastest guys. Now the MMP gave me those few tenths back. So its a nice "unfair advantage" one can have when running stock classes ;) Our fast guys have regular TC ESCs which aren't fast for stock class.

[Pdelcast]

Originally Posted by Lauri

Ok. I will then try to figure out what was the case. Patrick, could you only state some RPM range the Start Power is active? For an example up to 0 to 1000rpm?

Well, that has a complex answer -- it's related to the Kv of the motor -- high RPM, low turn count motors will be in "start" mode longer than low RPM high turn motors ... But in any case, the controller will drop out of "start power" controlled mode (and ramp current faster) in under a few hundred RPM worst-case. In some cases (like on a 17.5 turn motor) the controller is out of controlled start power at around 100RPM.

Thanx!

Patrick

[SunnyHouTX]

Lauri, this may be a silly question, but what's your gearing at 17.5T and at 5.5T?

Edit: also, what are the temperatures of the batteries prior to each race? Are they consistent?

[nativepaul]

Originally Posted by SunnyHouTX

what are the temperatures of the batteries prior to each race? Are they consistent?

Good point, the weather has got cold recently.

[Lauri]

Thank you Patrick for the answers. I will try to do some tests and figure out what was causing this weird issue.

Guys, don't point out the obvious ;) I was geared ok. FYI 17.5T I was geared somewhat slow 4.45FDR. Most other guys went as much as 4.0FDR. I didn't go that fast because I used the CHEAT mode and needed to keep the temps down. I could have gone 4.2FDR without going over 80C but didn't want to risk it last time, it was borrowed motor. 5.5T was geared 6.8FDR and it was the maximum I could go without overheating the motor. I gear by laptimes and check motor temps. LiPo came from stock race I think around 30C and droped to room temp 20C before the next start. From modified 5.5T it comes a bit warmer, maybe 35-40C max and drops to room temp. But this topic was about the MMP and Start Power setting which I didn't understand ;)

I'm getting a new LiPo just to be sure. I will run them back-to-back to see if it makes a difference. I'll be adding a external cap to the MMP just to save the LiPo from the pulsing current. Don't really like tha fact that MMP has very small internal caps. This can't hurt anything.