Kinetic/Ballistic Systems

[BrianG]

Originally Posted by NovakTwo

In the arena of car racing for which we have designed controllers, both brush and sensored brushless, I have never seen, (or read about on forums), any interest in current rating specs.

If anything, about the only spec racers have ever been particularly interested in is on resistance. I'm just speculating here, but maybe these current rating specs have been valued and emphasized more in controllers for air models or non sensored controllers. Especially a few years ago, when European/Asian esc mfgs started re-purposing their airplane controllers for surface vehicles.

Personally, I would be just as content if we deleted all these numbers in our esc spec chart. If the rated/braking current numbers were once meaningful, they no longer are. Years ago, when we began listing only the MOSFET stats, it was because our engineers could never figure out how other companies' garbage ratings were measured; so we selected this alternative method.

Well, the majority of people probably don't care about the current spec as long as it works without overheating when geared reasonably in the vehicle it was meant. And trying to rate them to match other companies' overzealous methods is just bring you down to their level.

[nitrostarter]

Originally Posted by NovakTwo

In the arena of car racing for which we have designed controllers, both brush and sensored brushless, I have never seen, (or read about on forums), any interest in current rating specs.

If anything, about the only spec racers have ever been particularly interested in is on resistance. I'm just speculating here, but maybe these current rating specs have been valued and emphasized more in controllers for air models or non sensored controllers. Especially a few years ago, when European/Asian esc mfgs started re-purposing their airplane controllers for surface vehicles

I can agree here. I just got into the world of Sensored 1/10th scale systems. The first question I was asked was about the resistance on the controller...

[lutach]

I have an idea. I'll make some phone calls and send some e-mails. It will be good if everything I have in mind works out.

Edit: Two e-mails sent and I'll wait for a reply, but will also make 2 phone calls tomorrow.

Do Li-Fe cells really need a voltage cut off?

[JThiessen]

Not from my experience. You will notice the drop in power - its significant. When you do, its time to shut down. If you keep running them after that, then yes, you can possibly damage a cell.

[JERRY2KONE]

Originally Posted by Erevocanuck

Do Li-Fe cells really need a voltage cut off?

According to all of the info provided by manufacturers a low voltage cut off is not required for LiFe cells. Like Thiessen stated when the LiFe cells are done there is a sharp drop in power and you will know it is time to stop and recharge. From what I have seen there is no real danger with the LiFe cells, and the power provided seems to be very similar or close to the same level as the LIpo cells without worry of catostrophic failure or fire due to over heating the cells.

Seems like a good laternative choice in my opinion over the Lipo technology, but how well they actually stand up against LIpo in performance is yet to be discovered or reported. Some feedback from those who have used them would be nice so we can weigh in on comparison.

[JThiessen]

I used 2S2P A123's in my Revo prior to going Lipo. In the same truck, the performance of the A123's was good - not as good as Lipo, but still a signifcant improvment over Nimh. Just off the top of my head, I would get 15-20 minutes of run time, compared to 20-30 on my lipos. And they charge so fast - 20 minutes or so.....I'd be just rotating packs off my charger and running them. Disadvantage is size - I tried setting them up as 3S2P but they were absolutely huge.

[Unsullied_Spy]

From what I've seen, LiFe cells drop off worse than a NiMH pack. When it's done, you know it.

[snellemin]

Yup when the A123 dump, it's basically empty. As of late I've vented a couple of my A123's from pulling an overdose of amps in my crt.5. It has a funny smell, but there are no fires and whatnot. When they are overheated at around 160F, they lose some capacity. I'm sure lifecycle goes down quite a bit.

I have one 3s1p pack now in the crt.5 that overheated quite a few time. Once cell voltage is lower than the rest. But I still get 1800mah out before the pack loses its marbles. And under max throttle it still puts out 7.3V(nomadio telemetry).

I asked that question because on the novak web site it said something to that effect

Another feature that can be fine tuned via Novak’s new PC interface is the adjustable Voltage Cut-Off parameter. This feature allows drivers to select a cut-off voltage value among a predetermined range of values for 2S Li-Po and Li-Fe battery packs. This voltage cut-off flexibility can improve a vehicle’s performance, while still protecting a driver’s battery investment.

-thats what it says on the link form this thread

[himalaya]

540A current spec came from the FET's spec @25°C trans.temp. 180Ax3=540A.

The 180A is listed in IR's IRF6691 datasheet, which was employed in earlier batches of Novak's GTB ESC, but later GTB switched to STK850 which did not mention this spec in its datasheet but Novak continued using it.

It's good Novak didn't quote this spec in red circle, they can improve the ESC performance to 260*3= 780A ESC simply by this.


I have to agree with lutach, a 90A rating for this small ESC would make Novak look more realistic and of a down-to-earth flavor, at least to those who know what the ratings are talking about.

[NovakTwo]

We took a vote at Novak and are dropping all of those "current" specs.

They are meaningless, confusing and unnecessary.

[JERRY2KONE]

Originally Posted by NovakTwo

We took a vote at Novak and are dropping all of those "current" specs.

They are meaningless, confusing and unnecessary.

I would believe that the trick is not to just drop all of your spec info, but to give us something that we can all rely on for accurate comparison. One of the main reasons we all come to forums like RCM is so that we can get the straight skinny from people who really do know what all of this info means. We are sure that alot of the companies use info that is not only somewhat untrue, but also very confusing. If you guys cannot really tell us what the truth is then how can anyone expect us to know what the truth is?

It would be nice if the major players in this could put your heads together and come up with one standard for everyone to go by, which would make things much simpler for the rest of us. Kind of like when all of the auto manufacturers came together and came up with OBD11 for computer analysis in trouble shooting codes, which is now a world wide system. I know that nothing like this is ever simple, but nothing changes if no one steps up and tries to make things better. With all of this goofy ESC info out there how can anyone figure things out?

[NovakTwo]

I don't want to repeat myself, but we adopted the soon-to-be-deleted transistor current info years ago when other makers of (probably) brush controllers were making ridiculous claims for their escs current handling.

Expecting all mfgs to adopt esc current rating standards would probably be expecting too much... Maybe where speed control current ratings are concerned there is no "truth", only "it depends".

We will continue to rate our controllers by the motor wind limit and number of cells; anything exceeding that range could damage the electronics.

[lutach]

Originally Posted by NovakTwo

I don't want to repeat myself, but we adopted the soon-to-be-deleted transistor current info years ago when other makers of (probably) brush controllers were making ridiculous claims for their escs current handling.

Expecting all mfgs to adopt esc current rating standards would probably be expecting too much... Maybe where speed control current ratings are concerned there is no "truth", only "it depends".

We will continue to rate our controllers by the motor wind limit and number of cells; anything exceeding that range could damage the electronics.

Didn't Novak just follow the same claims? We need data to back up such claims or at least the correct rating. Look at Castle and Tekin, they don't rate like you do. For example, the Tekin R1/RS ESC is rated for 104A when using the Ta 25C 26A rating and 76A when using the Ta 85C 19A rating of the On Semi NTMFS4833N. Now if I use he Tc 25C 191A rating the ESC would be a 764A and the Tc 85C 138A rating it would a 552A, but here is where things get interesting. The NTMFS4833N has a Pulse current of 288A which would give you a 1152A rating. How did I get those numbers you ask? Simple, the R1/RS uses 8 MOSFETs per phase, but I only multiplied the AMP number by 4 due to the H bridge design of a brushless ESC. Now the R1/RS has a total of 24 MOSFETs. If it's possible to get the part number for the MOSFET you use in your Kinetic ESC, we could come up with a better rating for it. Will it be less then the 540A rating yes, but I would respect the true rating more then the 540A out of the blue rating.

BTW, we are still waiting for an explanation on how Novak came up with the 540A rating.