Investigation ...6s1p or 4s2p, neu, cc neu...

[Pdelcast]

Originally Posted by phatmonk

Is the CC 2200 a copy of the older Neu 1515 series with a better purpose built case designed for surface use/1/8 trucks?

It's a Neu 1515 built under license from Steve Neu. Neutronics gets a royalty from every Castle/Neu motor sold.

We changed the case to seal it against dust/dirt/sand/etc.

[MrMin]

Originally Posted by Pdelcast

It's a Neu 1515 built under license from Steve Neu. Neutronics gets a royalty from every Castle/Neu motor sold.

We changed the case to seal it against dust/dirt/sand/etc.

and thats why almost nothing else can compare to it. It's very interesting how much detail went into its design and quality build.

[Pdelcast]

Originally Posted by MrMin

Three cheers for Patrick!

I'm impressed at the level of detail. You wont find any other esc and bl motor manufacturer giving this level of info and care to their obsessed customers. Simply amazing. Oh...I might be asking for more info... let me just swallow this first.

The material plays a role in the eddy current losses - It should be non conductive ferrous/magnetic type material and the higher the switching freq the higher the eddy currents... I need to look up the equations from years back...

At the moment gut feel looks like: BL Motor Efficiency losses accountable by
80% resistive (wire), 7% eddy current, 7% magnetic saturation, (rest on other losses such as variable load/good&bad gearing/)...??

Open to suggestions...

I'm pretty sure this will not be linear. I'm gonna see if we can work out the math so we can do an accurate simulation plot & material swap/switchout compensation test... Maybe I'll get bored before I finish this project..lets see.

The thinner the lamination material, and the less electrically conductive, the lower the eddy current loss at a given frequency.

We are using .2mm thick laminations -- very thin electrical steel.

The electrical grade is the M19 rating -- that is watts loss per pound on a standard scaled system. M19 is the best commonly available thin electrical silicon steel.

Most brushless motors sold for the hobby use .35mm M30 electrical steel, which is very cheap (about 1/4 the price of .2mm M19) and commonly available in China, but is a poor choice for brushless motors IMHO.

[jzemaxx]

Anybody do the calculations for this. I need to see if I can ditch my 5S parallel setup in favor of series 2 X3S (6S) and still get close to the same runtimes. 30-45min A-mains suck..lol

[MrMin]

Theme switch - quickly - Zippy batteries. I've kind of been obsessed about the fact that I've been reading zippies are tricky and not good etc...
I've been doing some basic calc....momentum.. 540 joules(thats 540 watts!) need to be dissipated over 1 second during braking.
The batt can handle about 1C, thats about 4-7 amps..maybe a little more. But we will see almost 100 amps...for 1 second..thats a long time in components lifetimes..

My idea is to cross 3 nice big zeners (with current limits)and 2 tvs diodes - I know its kind of overkill! on a tiny board which is between my batts and ESC (I have a loud maxpro buzzer there anyway - it reminds me when its time to put the batts to sleep). I've already done a spice circuit sim 3 times and it seems like it will work..

I'll give a list of components(I've got to source 3 x 5W(continuous) zeners and 2x1500W(burst) TVS diodes and a couple of current limit resistors..) and test the voltage etc... its all about "clamping".. When I've completed the "MrMin load dumper" or if you prefer "MrMin esc protector". BTW: Seems like caps will not help a lot, maybe with the ripple current and smoothing a bit.

BTW: A more elegant version would be active clamping/load dumping with IC's & power fets, but I'll see how well this works first...

What patrick said about the huge load is real. We got to keep the voltage below the 30v to protect the FETS.

Patrick, what do you think? I've done the spice sim and it works out..

This is part of this little investigation anyway...

[Pdelcast]

Originally Posted by MrMin

Theme switch - quickly - Zippy batteries. I've kind of been obsessed about the fact that I've been reading zippies are tricky and not good etc...
I've been doing some basic calc....momentum.. 540 joules(thats 540 watts!) need to be dissipated over 1 second during braking.
The batt can handle about 1C, thats about 4-7 amps..maybe a little more. But we will see almost 100 amps...for 1 second..thats a long time in components lifetimes..

My idea is to cross 3 nice big zeners (with current limits)and 2 tvs diodes - I know its kind of overkill! on a tiny board which is between my batts and ESC (I have a loud maxpro buzzer there anyway - it reminds me when its time to put the batts to sleep). I've already done a spice circuit sim 3 times and it seems like it will work..

I'll give a list of components(I've got to source 3 x 5W(continuous) zeners and 2x1500W(burst) TVS diodes and a couple of current limit resistors..) and test the voltage etc... its all about "clamping".. When I've completed the "MrMin load dumper" or if you prefer "MrMin esc protector". BTW: Seems like caps will not help a lot, maybe with the ripple current and smoothing a bit.

BTW: A more elegant version would be active clamping/load dumping with IC's & power fets, but I'll see how well this works first...

What patrick said about the huge load is real. We got to keep the voltage below the 30v to protect the FETS.

Patrick, what do you think? I've done the spice sim and it works out..

This is part of this little investigation anyway...

Lots of things that don't work look good in Spice....


Think about it this way -- A TVS is a large die zener diode. But until you have nearly the same die area in TVS as you do in FETs, then the TVS is just going to fail...

Remember that a FET can act as a zener diode -- they have what is called an "avalanche" rating. They can take a very large amount of energy -- but in an application like the MMM, it is usually not efficient to use TVS devices to protect the main FETs. In this type of application, the main FETs will still fail if you try to push everything too hard. You simply can't dissipate the energy in any kind of silicon device (within reason) -- you need to put it back into the battery...

I could spend the whole night discussing why -- but I probably won't convince you. I've spent 15 years designing motor controls, and still haven't seen a TVS be useful for anything other than protecting sensitive components like microprocessors. They simply can't dissipate enough energy to be useful in any other way -- and in fact typically can't take anywhere near as much excess energy as the main FETs themselves.

[MrMin]

What I mean is 4 power zeners(6 amps constant) in parrallel to draw power like a clamping device during the load dump. The TVS cannot dissipate the power.

[shaunjohnson]

i'm learning lots

(prolly already covered) but if i use a higher voltage battery (6s) then the current dump should go back into it easyer right?
as then the charge voltage can go up hence then the dump amps would come down...relative to the braking power.

it'd be nice to be able to have some way to get hold of this dumping power and like said before...let it slowly go back into the batt or get used by the ESC...
after braking usually follows a take-off, so then more power is used.
so why cant the current dump be shoved into a cap and then any exess into the battery?
cause that way the main high current dump should hit the cap, once the main first part is gone the rest of the current should be able to be sucked up by the battery correct?

shaun

[MrMin]

Either way the 540watts must be "eaten" when braking..in one second. I dont think 4s or 6s plays a big role in this. It is more to do with the internal resistance of the batteries and that affects voltage stability under load. Basically it is a matter of good or bad batteries.
parallel(4S): Internal resistance will be less if in parallel, so theoretically a parallel setup will help with braking, but more current has to flow, so more heat.
series(6s): Internal resistance will be more, but current flow less for same power. Braking will be worse, but with good batts it will be ok.

Band-aids -(With better batts you need not worry about this):
CAPS: You're going to need a 1-2 farad cap. to absorb that kind of energy 50v..That will be as big as your car!! or bigger. and very expensive. And then the voltage will probably be over 30v and goodbye to FET.
CLAMPING DIODES: TVS diodes are there for short bursts.. Power zeners will dissipate a few amps over longer periods of time, switch off rather slowly.. My hopes were on this method as its cheap. In order to sink the excess reverse current. I still think it has some merit.(sorry patrick!).
ACTIVE CLAMPING: Use a linear IC(based on comparitors) to clamp the excess load through a external power mosfet. There are some nice ones on the market to do this. I believe this will be the luxury solution, but more expensive than above solution.

It would be nice to store the energy than to throw it away, but what to do with it and where to store it?

Still - the mmm and your truck will last longer if you drive sensibly by being easy on the 100% gas and 100% brake... (You can set your xmitter to help you as well.)
For those that want to push it 120%, be prepared to buy more parts. (batts and drivetrain)


Remember that a loose connection or a battery disconnect during operation will be FATAL to your mmm.

I'm only thinking out aloud here, so dont go and do things and blame me for it.

[shaunjohnson]

yeah we never drive our trucks like mad men.
we run 6s because of the running temps are kept low.
lose connection is a good one to watch out for yes!!
would it be worth running dual deans?
shaun

[MrMin]

Well if you had two connectors then maybe it would help a *tiny*, *tiny* bit, but redundancy is always better..in case..you flip your batteries out while you are running... ..then..it might well be time to say farewell to your esc.

Back to 4s 6s etc...

I measured each cell in a 5s battery(junk test battery) and got 20,30,20,25,21mOhms... per cell. This means the total resistance is about 0.12 Ohms... Not good.
A good 5s battery will be about 0.055 total. Of course they are all in series.
A good pack will be:
6s=3s x 2= (3x (0.033 x 3) Ohms) + (3x (0.033 x 3) Ohms) = 0.198 Ohms
4s=(4x (0.033 x 4) Ohms) in parrallel = 0.0165 Ohms
This means that 4s should be able to eat more current. (that is if the chemistry can handle it)...But if you offset it against the losses due to low voltage high current&resistance in the wire then you probably can say it is about the same.

When you brake you are dissipating 550joules if 5kg car travelling 40mph. It looks like 180Amps(for 6s, for 4s=even more!) across the battery at FULL brake. This is really a lot - poor battery, because battery is used to 1C, thats 10 amps max ouch.. But then when you accellerate from zero at full power you will draw 180 Amps burst++...

A lot has to do with gearing in the end... How much strain you put on the esc and when....

I've just got both 4s2p and 6s1p(2x3s) setups.

[Pdelcast]

Originally Posted by MrMin

I'm only thinking out aloud here, so dont go and do things and blame me for it.

They blame me for thinking out loud all the time.