Advice needed on voltage to run a MAC 6T

[Ch00paKabrA]

I really did do my research, I promise. The only problem is that now I am more confused than ever. I am currently in possession of a MAC 6T that I intended to lace into a motorcycle rim and run it at 72 volts 40a. My goal is to be able to reach 35 to 40 mph for short periods of time and cruise around 25 to 30 mph. After reading a bunch of threads, one in particular about running a MAC 6T at 72v, the general consensus is that it is lunacy.

I have also read threads where it is stated that MACs run great at 60v. So are the additional 12 volts a MAC killer or does it have more to do with the amps.

I have controllers and a charger in my possession and 200 Samsung 18650 25R batteries ordered (not sure when they will show up). I can configure them into any voltage so what is my best option? Can I run this thing at 72 volts? The controllers are one 20a max controller and one 40a max controller.

Any input would be greatly appreciated. If I wasted money on the charger and the controllers, so be it. They weren't very expensive anyway. I just don't want to melt the motor.

Another option is to put the MAC on my beater and run it at 36 or 48 volts. I could then use a different motor on the higher speed bike.

Let me elaborate a little on the uses of the two different bikes. I have one that I frequently pull a bike trailer around that I use for going to the beach (1 mile away) and grocery stores, etc. Just really bumming around. I have a MW Motors 36v 250w rear hub motor that I ran on 72v 10a and didn't have any problems, but it is a torque wind. It only does 16 mph in a 26 in wheel (equivalent) at 36v. After reading all of the warnings though, I switched it back to 36 volts. On 72 volts, it would do over 20 mph. I could just put the MAC on this bike but I am not sure how well it would handle a trailer since it is a speed wind.

The MAC is slated for a Giant DH Comp and I have a family member that lives around 20 miles away. It is flat here with very few hills. The only reason I wanted the higher speed is because there are highway entrances and exits that I must cross and the cars are generally doing around 40 mph or so and it is a bit hectic trying to get by them. I want to be able to burst up to around 40 to get through these danger zones and then slow it back down. Also since she lives 20 miles away, I didn't want to take an hour to get there.

200 25R batteries 20S 10P would have given me 72v (82v actually) 25ah. I figured that would be sufficient and I can recharge while I am there.

I hope that is enough info as to my intended use and expectations.

So here is the deal. I set a budget for the 2 bikes of $5,000.00 I am completely done with the "beater" and that came in at around $1,300.00. I have everything for the Giant DH Comp in my possession except the batteries but they are paid for and I am into it for approximately $2,200.00. Therefore, if I am going to stay in budget, I only have about another $1,500.00 to spend on any changes to the plan. I like the fact that I am under budget and would like to keep it that way if I can. I was going to buy a really nice brand new fork for it If I can come up with a way to meet my needs with what I have spent so far or just needing a new controller and charger.

Thank you in advance for your help.
'Cal

 

[motomech]

I'm no expert on Mac's, but this is from Paul at EM3ev:

The 500W Mac motor is recommended for use at 36V or 48V with recommended controller limit of 25-30A but this is really dependent upon the application and the motor winding that is used. We do recommend our Infineon EB3 controllers to ensure plug and play connections with good functionality. The slower wound motors such as 12 or 10T will work well with the 6 fet, but the 9 fet is recommended for the 8T and possibly the 12 fet for the high speed 6 T if they are used with wheels larger than 20

Specification:

6 turn high speed motor - 400rpm loaded at 36V.

As a guideline you can expect approximately the following real world speeds for the above windings on 12S LiFePO4 battery pack (approximately 38V under load) in a 26" rim on the flat, no pedaling with a rider plus bike weight of approximately 130kg total (286pounds):

6T - 45kph (28mph)

There is no equivalent to the 6T on the Ebike CA simulator, but I would think that 60 V would supply enough speed(for me anyhow).

Paul's advice on the relationship of motor winds and type of controller is sage, the 6T will eat up the Amps. You could adjust\limit them with a Cycle Analyst.

 

[Architectonic]

48v is more than enough for a 6T. Chances are you will damage the clutch mechanism over time running 72v (the gears are strong, but the rest, well... depends on how you treat it and how many miles you do).

 

[dogman dan]

I haven't personally gone out and fried mac motors. But yeah, I do think its lunacy.

You could lower amps enough to make 72v a more reasonable wattage, but then you'd just get a slow to accelerate bike, just when you need it fast.

You will be better off to run 48v, but enough amps to get across those roads in a brisk fashion.

When you do fry the mac, replace it with a dd motor. It will last longer on 72v.

 

[ebike11]

I also have a MAC but an 8T
I am using a 72v battery and with em3ev 9fet controller
I know its overvolting it but Id like to have to power there now and then, not for running 72v for a
long period of time.
It stutters BADLY mid throttle but smoothes out when finally WOT
I do have a CA v3 so Im gonna try an mess around with the settings

Its strange because my previous Bafang 8fun code 12 never stuttered on 72V
so before purchasing the MAC I assumed it wouldnt stutter either
since its a more expensive well built rear motor...strange

Im sure your 6T will stutter too
My controller is 30A

 

[Ch00paKabrA]

I also have a MAC but an 8T
I am using a 72v battery and with em3ev 9fet controller
I know its overvolting it but Id like to have to power there now and then, not for running 72v for a
long period of time.
It stutters BADLY mid throttle but smoothes out when finally WOT
I do have a CA v3 so Im gonna try an mess around with the settings

Its strange because my previous Bafang 8fun code 12 never stuttered on 72V
so before purchasing the MAC I assumed it wouldnt stutter either
since its a more expensive well built rear motor...strange

Im sure your 6T will stutter too
My controller is 30A

Thank you all for the comments I appreciate the advice. I am also in possession of 2 of lyen's metal gears for it. I also dropped it and broke the casings so while I was ordering new casings, I got a new clutch for it as well.

I thought it needed a new clutch because I got it used and when it was new to me, I hooked it up on my 36v 250w controller and and it stuttered very badly off the line. to the point that it was impossible to start with motor only, I had to pedal first.

@ebike11: What happened to the Bafang? Did you wind up frying it on 72v? There is a member here with a code 10 in the sales section. I was seriously contemplating buying it since he has a video in the thread showing Kepler doing wheelies on a stealth running at 72 volts 2000w. The video didn't show if the motor was a smoldering heap afterward though :lol: :lol: d

One thing that I did not buy is a cycle analyst. I think I will order that right away.

I am going to wait until I get the cycle analyst to hook anything up and run it. I guess you can expect a lot of cycle analyst questions from me in the future. I will also order a 48v 1000w 15 fet controller for it. then I will do some careful trial and error.

Thank you all again.
'Cal

 

[ebike11]

Hi
oh no no I just sold my Bafang..but I did notice the controller connections were melting coz of the heat. My fault since a 36/48v Bafang isn't supposed to use 72v
I thought a more heavy duty motor like the Mac would handle the power better after reading all the positive reviews.
I do love the Mac much more...just gotta work on the stuttering issue

 

[Drunkskunk]

Considering the MAC is good for around 1500 watts, and to hit 40 you'll be pulling 2000-2500 watts, you're asking for a melting. If you want this kind of speed and power, you're looking at totally the wrong kind of motor.

 

[teklektik]

It sort of looks like you have gone down a Bad Path.

Here is a quick plot of actual 6T dyno data for 48V and 60V operation with a Load Line superimposed (as in ebikes.ca simulator):


You can draw your own conclusions from the plots, but here's a few thoughts - with which you may or may not agree :

MACs are generally good for no more than 500rpm or so because of losses and the first thing you see is that around 40+mph you are maxxing out. This your target speed so this is okay, but things go downhill after that.

At 60v, the MAC will top out at about 41mph but the motor power is 2500W with an additional 800W being dumped as heat for a total battery consumption of 3300W (over 50A). A MAC can dissipate 400W or so after which it begins to overheat, so at 800W of waste heat the motor is pretty much only good for very short sprints. This is your intended use, so at first glance the huge waste heat might be acceptable... However, the really bad part is the 2500W power level needed to achieve this speed -- the clutch is likely to seize the first time you re-engage the motor at speed or try a WOT getaway - simply too much power for the clutch. You might address this with a CA V3 and throttle ramping, but you are way over 'optimistic-wild-claims' max of 2500W and twice the 'reasonable' max of 1600W. This just looks Bad.

At 48v things are better, but running flat out (35mph) it's still dumping 500W of waste heat so you are either on the edge of overheating or into it. Total battery power is about 2100W = 1600W motor power + 500W waste. Again, you are riding the motor pretty hard - this is why EM3EV recommends no more than 48V for this motor. If you have a heavy throttle hand, well...

It's worth noting that this 48V curve is what you get by running the motor at 60V at partial throttle with some current limiting thrown in. A CA with 3-position switch to tame the current would let you run this curve at 60v with a 'boost mode' switch option - but the 'partial throttle' power levels can still be substantial and the boost level power remains a recipe for disaster. Clutches don't need prolonged abuse to eventually fail - they can simply fail catastrophically on the very first slamming power impact. I'm sure some member can pipe up that he does this all the time, but EM3EV doesn't recommend it, and the dyno data doesn't make this look like reliable commuter transportation that is operating with a solid design margin.

Considering the MAC is good for around 1500 watts.... If you want this kind of speed and power, you're looking at totally the wrong kind of motor.

+1.
The basic requirement of ~2300W motor power (not battery power) to achieve 40mph is still there making any MAC a poor choice. DD looks like what you really want to achieve the speeds of interest. If you have used the ebikes.ca simulator, you know the 2300W motor power to achieve 40mph relies on the bike and terrain - not the motor - a DD motor will need to develop the same output.

As far as demoting this to the beach beater for use towing a trailer, things are not optimal. This motor does not make a lot of torque off the line where power is controller-limited - and the 6T eats Amps. What power you do get will not be done efficiently under heavy load -- it will head into overheating pretty quickly if you flog it in sand or with a heavy trailer. But - compared to your existing smaller motor and it's ability to handle the needed load, the 6T would probably be serviceable at low voltage. Or your could sell it.

48v is more than enough for a 6T. Chances are you will damage the clutch mechanism over time running 72v (the gears are strong, but the rest, well... depends on how you treat it and how many miles you do).

I am also in possession of 2 of lyen's metal gears for it. ... I got a new clutch for it as well.

Large gear motors (BMC, MAC) switched gear material a couple of years back. Most of what you read about damaging gears is in old posts, relates to small gear motors with nylon gears, or is just uninformed conjecture. You don't need or want steel gears (they will chew up the sun and ring gears). The real weak spot is the clutch. That said, using a CA V3 will allow you to pour pretty big watts through the motor at the expense of poorer throttle response as the CA ramping applies power slowly to avoid scaring the clutch to death.

 

[Architectonic]

Large gear motors (BMC, MAC) switched gear material a couple of years back. Most of what you read about damaging gears is in old posts, relates to small gear motors with nylon gears, or is just uninformed conjecture. You don't need or want steel gears (they will chew up the sun and ring gears). The real weak spot is the clutch.

Agreed. I'll say it again, you don't want or need steel gears in a BMC or MAC motor.

 

[Raged]

I run a MAC 10T which was purchased in April and punish it pretty hard as an all round commuter (havent tried actual bush trails yet). I run the 12 FET 40A controller with lipo and off the charge voltage is about 58V... so I'm pushing about 2300watts to get a top speed of 30mph which I feel is fast enough for our crappy roads and a hard tail bike. Check out my sig for my build thread (last page has video). I did a tear down to see how much damage there was at the 1000km mark and it still looks new.

I'll agree with the others in saying that the 6T probably isnt the motor you want for that speed and acceleration. Alternatively, you could find another way around where you're not risking your life crossing a highway (should be an underpass somewhere)...

 

[spinningmagnets]

Ben Chiu is running 60V on dual MAC 6T's, but...a SINGLE motor at 40-MPH will die quickly.

He is using TWO of them (double copper mass),
They are the upgraded MACs with the thinner laminations (to avoid eddy current heat at higher RPMs)
They each have temps sensors so the Cycle analysts can limit the amps when the heat rises

http://www.electricbike.com/custom-build-gallery-duty-cycle-awd/

The other option I have seen is...a rear Crystalyte H35/H40 that is ventilated to let the heat out, using 100V

http://www.electricbike.com/big-hit-fsr/
http://www.electricbike.com/nicks-etownie/

 

[ebike11]

What if you are only using a 6/8T on flat roads with no hills...would that power still be a problem??
Plus a CA v3 can monitor the tempertaure and you could always slow down if getting hot

 

[spinningmagnets]

Ben Chiu started out using MAC 8T's on his dual motor build. Even just using 50V, it would climb exceptionally well and could take a LOT of heat.

The MACs have a 22mm wide stator, with two equaling 44mm wide (which is a rough measure of its copper mass), and the Cromotor has a 50mm wide stator.

You could also use a 9C on the rear at 50V X 25A = 1,500W (28mm wide stator), and a MAC on the front. The 9C gives you an efficient and cheap option on the flats to run one motor to 30-MPH, also providing regen-braking. The MAC has an integral freewheel, so it can coast on flat land while mounted on the front. MAC 10T at 50V does 26-MPH and you would kick it in when you get to a hill for 2WD.

 

[DAND214]

Aftr all the posts, no one asked what size.

I intended to lace into a motorcycle rim and run it at 72 volts

72v is a no no but 60v could live if it's not a 26" wheel.


Dan

 

[teklektik]

Aftr all the posts, no one asked what size.

I intended to lace into a motorcycle rim...

... because we looked at the build in his sig...

 

[Ch00paKabrA]

Thanks. Initially this build was to be a dual bafang 48v 500w build. but I worked a trade and ended up with the MAC 6T. If I have to replace it, it is really no big deal. It seems that the Bafangs can handle 60 volts without too many issues and I would double up on the phase wires like I did with the MAC. It seems like I might just wind up going with the original plan. I am not a big fan of the size of the direct drive motors but it is worth consideration since I would not be saving weight with a dual motor set up.

One of the reasons that I gave up on it was that I read a thread on the forum and there were about 100 reasons not to do a dual set up. At this point, I think it would be a good idea to take a step back and re-evaluate.

The possibility of adding another 6T to the front is definitely intriguing. Even with another MAC, it would probably be best to turn down the volts. If I add another MAC 6T to the front, would I be able to run 60 volts and do you think that the 200 18650s can handle it if both motors are under power? they are 25Rs and rated at 8C each. That would be 12 in parallel and since I just blew a grand on them, I really don't want to take too many risks with them.

Perhaps a good question to ask would be this:

What is a simple way for me build an ebike that will go over 30 miles per hour while I don't have to constantly monitor everything to keep it from blowing up, burning up, or generally screwing up?

Here is what I have to work with:

1 giant DH Comp with custom drop outs.
200 Samsung 18650 25R cells (on the way)
Wheels are 19" Prowheel rims with IRC GP1 19 x 2.75 2 ply tires (they were 3 pounds lighter than the Shinkos)
2 Marzocchi Drop off triple forks. One with a 20mm through axle the other with standard 10mm drop-outs (so a front motor would be easy) Both have just been rebuilt and are in perfect working order.
1 72 volt 40a controller
1 72 volt 20a controller
1MAC 6T rear Hub motor

If I need to scrap the 72 volt controllers that is fine. If I need to add another MAC 6T, that is fine too. If I need to scrap the MAC and get a DD, then that is also OK.

Thank you Spinning Magnets for the links to those other examples and thank you teklektik for the informative post. Also thank you to everyone else who posted. It was very informative and helped a lot. Basically, I got the motor and tried to build a bike around it and had unattainable expectations. Basically, I am still OK, budget wise and since the MAC didn't cost me any actual dollars, I am only out $150 or so in controllers and the charger.

The construction of the bike is almost done so I guess it is like starting a new build.


Edit: I just finished reading and rereading Spinning Magnets' article on the dual MAC 6T and it seems like this might be a good way to salvage this project. the only issue I think I might have is running both motor/controller combos off of 1 throttle. When I initially envisioned a dual motor bike, I thought that separate throttles would be a wise choice. Reading his article though, I think I understand why the single throttle is better. I just don't really know how to do it yet.

 

[motomech]

I think I understand why the single throttle is better. I just don't really know how to do it yet.

Maybe this way;

http://www.bmsbattery.com/controller/607-s06-250w-imitation-torque-square-wave-controller.html

 

[Drunkskunk]

Your front fork isn't suitable for a front hub motor, especially at the speed and power you will be running. Is there some reason you are resisting going with a direct drive motor of a size and power level that can handle what you need?

 

[Ch00paKabrA]

Your front fork isn't suitable for a front hub motor, especially at the speed and power you will be running.

Why isn't it suitable? It is a Marzocchi Drop off Triple (I know it is not top of the line but...).

After racing my R1 in WERA for years and Riding Motocross most of my life, I am familiar with the inner workings of a motorcycle fork. I have both a 20mm through axle fork and a standard 9mm drop out fork. I rebuilt both. They are not cartridge forks but I have the experience to compare them to many different sizes of MX forks and they are comparable to a Honda XR100 fork in construction and the quality is a bit better.

My daughter rode her XR100 at around 20 to 30 mph off road. I understand that the fork will be under power, but that is what torque arms are for. The only other issue would be the weight affecting the damping. I believe increasing the preload air pressure in the left fork from 15 to 20 psi will help and not affect the performance of the seals, Also, a slight increase in the psi in the right fork from 45 to 50 should have the same effect on the rebound. While the MAC will add weight, it is fairly light compared to a DD motor. My initial plan was to use 2 Bafang BPMIIs and the MACs are similar to them in weight.

This is not an off road ebike and will be strictly ridden on paved roads. I generally put my pedal power mountain bike in a trailer and tow it to the park then go crazy.

Ask me about my choice of batteries and I can't tell you why, other than that I read a few threads where others said they were good.

Ask me why I chose a DH Comp, why I chose a particular BMS, or throttle or controller and I will tell you the same thing.

In this entire build, if there is one thing that I am entirely certain of in my own rite, it is that the forks are sufficient for the task.

I know that there are many more sophisticated forks but this fork came standard on many high end DH bikes in 2004 through 2007. I am not sure why you would make that statement because you did not elaborate but I respectfully disagree.

Is there some reason you are resisting going with a direct drive motor of a size and power level that can handle what you need?

Yes, It is precisely for the reason that I believe that you disagreed with my selection of forks. A direct drive motor is heavier than a MAC and not by a small margin. Putting that much weight out back will put a strain on the rear suspension. Much more so than the MAC will have on the front forks. Add to this that I extended my rear swing arm by 2 inches for tire clearance and the increased leverage of all that weight is multiplied.

In addition to that, 2wd is cool. :lol: JK

I had hoped that a single MAC in the rear would be sufficient but it is appears that it is not. Shame on me for not doing my homework better. 72 volts... what was I thinking But it's all good. At least I found out before I melted the MAC.

Here is the link to the 2wd bike that will serve as my motivation/inspiration for the completion of this build.

http://www.electricbike.com/custom-build-gallery-duty-cycle-awd/ (Thank you SpinningMagnets)

Thank you again to all who have responded. I have decided to switch to a dual MAC 6T build similar to Ben Chui's and have just ordered the parts to do so from EM3EV.

As a bonus, I am still within budget.

 

[motomech]

well, if you survived racing an R1, I guess you can survive a Mac on the frt. :lol:
I've run frt. motors, ranging from 600 to 1200 Watts on some nice Bomber forks and although I never have had any concerns of breaking the drop-outs, some issues start to crop up around 1000 watts.
Traction for one. With a hard-start controller, care is needed of surfaces with less than optimal traction. Nothing uncontrollable, just saying.
More disconcernig to me, you can feel the torque taking up the slack between the inner and outer fork tubes. No, the bushings aren't worn, but of course there is some clearance and I can feel it during a hard start, and it doesn't feel good. A soft-start controller. or better yet, a delayed frt. start when the bike is rolling and this is a non-issue.
As far as weight on the forks, you know the motor is there but it doesn't really effect the handling. But my motors are mini's, ranging from 2 Kg. to 2.3 Kg. I would think a motor over 4 Kg. would deffinately be noticeable.
With my Rocky Mountain, I'm using systems, viewed as a single drive are considered all wrong. Runt motor w\ a high-speed wind and lots of Amps. Recipe for a toasty motor, but around town, it works fine and nothing over-heats. On those rare occasions when I need to run flat out or tackle a long steep hill, I engage the frt. motor, they split the load and I'm in "never over-heat" territory.
But understand, AWD complicates things bit, extra controller to mount, more wires, etc.
There are a number of ways to work the throttles. Sometimes, you can just split the 5V feed with no ill effects. D8veh added an extra Hall sensor to one half-twist., or maybe trying the cool dual controller system I linked. I use two throttles, a half twist w\ a thumb beside it. Sounds awkward, but I actually feels quite natural. I keep the rear motor on cruise most of the time and add the frt. when needed. But we are talking mini's here and I'm not sure that would work with a powerful unit.
There is nothing that says you need to use two identical motors, but I would recommend that they have simular winds.
To that end, why not try what you got and see what you might need to do in a way of a frt. motor after you test drive.
Although I would drop the Voltage from the planed 72V. If your 72v controllers don't have a non adjustable LVC that will mess you up, there is no reason they won't work fine @ 60V.
Time to stop planning(worrying?) and build :lol:

 

[Ch00paKabrA]

Thanks for the advice momtech. I will be dropping the voltage. The BMS and charger that I ordered from EM3EV are 14S or 58v. I am getting some advice on how to work the single throttle. to start off, I may just run two separate twist throttles and ease my way into tackling the electronics involved with a single throttle. I have a matching set of right and left hand throttles so the rear initially be on the right and thr front on the left.

There are a lot of people that battery boxes to put on the fork. Since the DH Comp has a lot of room in the triangle, I don't need to do this. Instead I will be building a controller box for the front.

check these out:



32mm poly urethane sway bar bushings. I believe these would make an excellent mounting system on the 32mm stanchions on the dual crown forks. I think I have the controller mount worked out.

Thanks again. The waiting part has begun again. All parts for this build have now been ordered.