MAC 8T on 16S lipo?

[srtgumbee]

HI all,

So I have worked out that a MAC 8T is needed for my goals of a commuter 40km/hr cruising most of the time, and 50km/hr + for short bursts so I can merge with 50km/hr traffic when needed (a couple of 500meter bursts at most). I will be using 26” wheels a 1.5” slick tyres. The commute is only 9km to work and 9km back, I have the option of charging at work and at home if needed. For this reason, I'm looking at using a small lipo pack (with high discharge rate) and I'm aware of the possible risks using lipo.

It seems a 12S pack might not quite get me upto 50km/hr and I need a higher voltage? Comments on this are welcome!

A 59.2V nominal 16S (4 x 4S 5000mah packs) is appealing as I can easily parallel up 2 x 8S packs for charging using a RC charger. Has anyone used the Mac 8T on such a voltage or higher? I would love to hear some comments regarding:

- Speed?
-Controller used? I'm looking at EM3ev 9fet high voltage controller, or should I be looking at the 12fet version and reducing the current in software.....eg 25 or 30amp limit as not to stress battery and/or motor
-Throttle response – Does it get twitchy at high voltages?
-Any other problems ?

Thanks Steve

 

[teslanv]

I've been advised by Paul (cellman) that I can run up to a 20S LiPo in his MAC 8T.

I'd get the 12FET IRFB4110 CONTROLLER, and derate it with the CA.

If you are only building a 5 Ah pack, I'd probably set the max current to 25A or 5C. 20C is possible on even the cheap packs, but they die much faster at higher discharge rates.

 

[deffx]

I use 15s 63v hot off the charger, been lucky so far, others have melted quickly, but I'm only 70kg, I also get kph to voltage pretty much, ie 50v=50kph on 26" hook works

Really cannot believe Paul recommends using 20s, 15s is roughly 500rpm any more is only going to be wasted too heat

I run a 12fet 45 amp peaks, yes the throttles twitchy, the Macs very torquey,

Let us know how you get on

 

[neptronix]

He really said that?
I ran a 8T on 72v/56A in a 26" wheel ( those amps are needed to hit top speed ) and it got ludicrously hot in a short period of time and melted the gears.
If you have a CAv3 and a temp sensor readout, you will see it get hot very fast on 20S, unless you're talking about 20S lifepo4... lol.

16S is a bit much for an 8T; you'll also overheat it, but that'll happen at a slower rate. I could get my MAC pretty hot on 15S over long rides at 35-39mph..

I've been advised by Paul (cellman) that I can run up to a 20S LiPo in his MAC 8T.

I'd get the 12FET IRFB4110 CONTROLLER, and derate it with the CA.

If you are only building a 5 Ah pack, I'd probably set the max current to 25A or 5C. 20C is possible on even the cheap packs, but they die much faster at higher discharge rates.

 

[recumbent]

I'm on my third ebike build in 10 years , and 14s lipo is the sweet spot for speed (50km/h) and not too much weight.
Remember, your riding a bike, 50 km/h is very fast for these frames.
Personally, I would not go over 1600 watts with a geared motor if you want it to last.

 

[dogman dan]

The higher the voltage, the twitchier the throttle will be, for sure.

16s sounds awkward, at least for stock controllers. I can see the appeal though, since two 8s chargers will do the whole thing at once, and it divides by 4. A few more mph is always appealing too.

I did a short ride on a fast wind mac, and I was very much unimpressed. I found a 20s setup on a slower wind dd motor much nicer to ride, very perky. The slowest dd motor cellman sells, with 20s is a very sweet ride. Though you may give it 3000w leaving the stop sign, it will cruise all day at 50 kph since that only will use about 1000w. With a 72v 40 amps controller, you will take off nice and quick, almost as fast as small motorcycles. You will blow away a fast mac with a 25 amps controller running 48v.

I am biased, I live where it's hilly, and the asphalt melts every summer. The motor needs all the help it can get to stay cool where I live. I have been preaching the slow dd motor on 72v for years now, and nobody listens. But a few that did have been really happy.

 

[teslanv]

I should note that my MAC 8T would be going on a 20" Wheel, so I am sure that makes a difference on Max. Voltage. Also I'm planning on pairing it with a Lyen Mini-monster 6FET 4110 Controller.

 

[wineboyrider]

AFAIK the mini monster won't run sensorless on the Mac motors, but it will run with sensors. It runs my high speed wind BMC fine.....

 

[teslanv]

AFAIK the mini monster won't run sensorless on the Mac motors, but it will run with sensors. It runs my high speed wind BMC fine.....

My Controller is the Sensored verison. Is the MAC 8T a Sensored Hub?

Lyen Does make a Sensorless Mini Monster as well...

 

[teklektik]

I've been advised by Paul (cellman) that I can run up to a 20S LiPo in his MAC 8T.

I should note that my MAC 8T would be going on a 20" Wheel, so I am sure that makes a difference on Max. Voltage. Also I'm planning on pairing it with a Lyen Mini-monster 6FET 4110 Controller.

20" vs 26"? Only telling part of the tale can be misleading - particularly for the uninitiated....

Here's a quick comparison of 8T on 20s with 20in vs 26in wheels from an experimental MAC simulator:


The 26in wheel case is dragging down about 3kW (40A limited by controller) while the 20in wheel is pulling about 2kW (26A). One of these motors can safely shed ~400W so the 20in case is definitely warm but the 26in is heading for a meltdown.

The 20" wheel casts Paul's statement in a bit different light....

 

[Observator]

Any chanse you want to share that simulator?

 

[neptronix]

I should note that my MAC 8T would be going on a 20" Wheel, so I am sure that makes a difference on Max. Voltage. Also I'm planning on pairing it with a Lyen Mini-monster 6FET 4110 Controller.

Oh, you should have mentioned that, it would have saved me a lot of typing :lol:

I'm gonna guess that a 20" wheel tops out at ~39mph on that voltage, and can't say how the continuous power will be. All i know is that the torque is going to be out of this world; like a Crystalyte HS35xx or larger in a 26" wheel.

I'm not sure if you'll bump into a problem from the resulting increase in eRPM, as the motor already has a super high eRPM. But if you don't have a problem, the worst case scenario is that you need to limit yourself to say, 35mph or so.

Genuinely curious to see someone try it.

 

[teklektik]

Any chanse you want to share that simulator?

Not really - it's a work in progress...
I can post stuff like the above where the results have a high confidence, but in its current form it could easily mislead as it wanders into less reliable areas of operation - which would be Bad.

The present plan is to at least post up some tabular results for common configurations and comparisons.
Thanks for the interest!

 

[dogman dan]

I tend to think and then write thinking 26" or 700c until told otherwise. Sorry, 20" wheel changes everything.

 

[teslanv]

Sorry for the initial misleading info. Looks like wheel size makes a big difference on the Mac 8T.

The Lyen Mini Monster Controller is rated for 20A to 25A Max Current, so I won't be putting much more than 2kw through the MAC with a 20S LiPo.

I'd be happy with 35 MPH on 20" wheels. It's going on a BMX frame, so I am anticipating a scary, fun ride, with plenty of head and body protection. - What I am not sure about is torque off of the line. It an 8T going to wheelie bad with a 20" Wheel? - Would I be better off with a 6T (Lower torque, higher top speed)

 

[Observator]

Not really - it's a work in progress...
I can post stuff like the above where the results have a high confidence, but in its current form it could easily mislead as it wanders into less reliable areas of operation - which would be Bad.

The present plan is to at least post up some tabular results for common configurations and comparisons.
Thanks for the interest!

That's understandable, how about a request?

System A: 26" wheel, 12s Lipo, Limited to 35A
System B: 24" wheel, 12s Lipo, Limited to 35A
System C: 24" wheel, 18s Lipo, Limited to 25A

Sorry about the hijacking!

 

[neptronix]

Any motor changes when you put it in a smaller wheel than the 26" it was typically designed for. Torque goes up, top speed goes down.

Dude, 20" on a short wheelbased BMX bike is going to be a total wheelie machine unless you limit the amps significantly.

35mph on a bmx is going to be a very hairy ride either ways. Small wheels, no suspension, short wheelbase... twitchy as hell.
I don't recommend it in the slightest.

You also probably have 115mm dropouts. That's a problem.

In fact, with a 20" wheel, since the wheel size is so small, you could use a lesser motor and NOT have a wheelie machine, but something that is more easily controllable up to 30mph. Think about some smaller geared motors on high voltage.

 

[teslanv]

Any motor changes when you put it in a smaller wheel than the 26" it was typically designed for. Torque goes up, top speed goes down.

Dude, 20" on a short wheelbased BMX bike is going to be a total wheelie machine unless you limit the amps significantly.

35mph on a bmx is going to be a very hairy ride either ways. Small wheels, no suspension, short wheelbase... twitchy as hell.
I don't recommend it in the slightest.

You also probably have 115mm dropouts. That's a problem.

In fact, with a 20" wheel, since the wheel size is so small, you could use a lesser motor and NOT have a wheelie machine, but something that is more easily controllable up to 30mph. Think about some smaller geared motors on high voltage.

I think I have the Drop-out dilemma figured out. I can get a front wheel kit and swap out the side plate for one with a thread for my Rear Sprocket and add some spacers at the shaft. - Should net about 115mm to match my drop-outs. - Worst case is I forcibly widen my drop-outs to match the motor/shaft.

As for torque - That's what I am note sure about. I can experiment with Battery Voltage - Maybe scale it back to 16S or lower if I can't keep the front wheel down with 20S, and also limit the amps. - I am assuming there will be a bit of trial and error with this build to get something usable... That's part of the fun, isn't it???

 

[wineboyrider]

Teslanv wrote:My Controller is the Sensored verison. Is the MAC 8T a Sensored Hub?

Lyen Does make a Sensorless Mini Monster as well...

The Lyen 6 fet mini monster will run sensored as it has hall wires and/or sensorless with many motors, but it has more timing issues and is designed to run best on the bafang mini motors, but honestly it runs my Direct Drive yescomusa motor great with hall sensors, but roughly when run sensorless..

 

[neptronix]

Don't run anything other than an EB3 sensored controller on the MAC.

This is the most difficult hub motor for any controller to ever encounter. Before the EB3 came out, us folks using the EB2 or lesser controllers had all kinds of problems.

 

[teslanv]

So it sounds like this Lyen controller is a No-Go on the MAC 8T???

Below is the specification:
Model: EC-064110-LYEN EDITION
Start immediate controller
Chipset: XCKJ8B116A (same chipset being used as in the 18 FET controller)
Circuit board version: EB206-A-3
6 x genuine IRFB 4110 MOSFET N-CH 100V

 

[neptronix]

EB2 on a higher than average RPM wheel with the most difficult to drive hub motor? no way, it'll run like crap!

 

[teslanv]

EB2 on a higher than average RPM wheel with the most difficult to drive hub motor? no way, it'll run like crap!

Thanks for the head up.

Guess I'll save the Mini Monster for the Wife's 26" DD Hub...

 

[spinningmagnets]

If you haven't ordered it yet, the "upgraded" MAC has thinner laminations, so it will have fewer eddy-current losses due to higher motor-RPMs.

The upgraded unit is worth the extra price for the temp sensor alone. A fried motor costs a lot more than a temp sensor and thinner lams...

 

[teklektik]

If you haven't ordered it yet, the "upgraded" MAC has thinner laminations, so it will have fewer eddy-current losses due to higher motor-RPMs.

+1
Absolutely - this is a 'must' for this high rpm setup.