My second e-bike: Reality Check? (Pretty please?)

[Joe Perez]

So I've decided it's time to upgrade. And after much searching and reading of past threads I'm hoping for the counsel of those who have gone before to either verify that I'm headed down the right path or tell me why I'm being a complete idiot.

For the past year, I've been zipping around on a basic AmpedBikes rear direct-drive lithium system. It's been a good introduction to the world of e-biking, but I feel that it's time to upgrade, both the bike itself (from a cheap, steel-framed department-store model) and the electric assist system.

My daily commute is about 12 miles roundtrip, and consists almost completely of various inclines- there's hardly a flat section to it, as is the nature of life in coastal southern California. Most of the grades are fairly moderate (say, 5% for the length of a half-mile or so), however there are a few sections of 10-15% on which I struggle mightily to pedal while simultaneously operating at full throttle just to keep from stalling the motor. And that's the part that's really causing me grief.

Understand that this is a "sane and reasonable" daily-commuter bike. I'm not looking to build a 50 MPH downhill screamer, nor will I be climbing straight up a wall while towing a 200lb coffee-roasting trailer (though I must say, that was a pretty cool build.) What I'm looking for is a system that will be able to cope with the few severe 15% inclines without giving me a heart attack (I'll admit that at 6'1 and 200 lbs I'm still in less than optimal shape), while also being able to provide a moderate assist while I'm pedaling to maintain 20-25 MPH on the less dramatic slopes.

From everything I've read, Cell_Man's geared MAC motors seem to be the way to go right now. And while I'll admit to being slightly leery of doing business with a company in China (particularly when it comes to things like spare parts availability such as clutch / gear rebuild packages) I haven't read much in the negative column.

My thinking, at present, is something in the neighborhood of the 10T "Torque" motor on a 26" wheel with the 30A IRFB4110 controller, along with a battery in the vicinity of 48-60v and 10-12 Ah, wherein it seems that Cell_Man again has things nicely in hand with his 52v, 11.5 Ah, 30A BMS "Triangle" battery.

Is this overkill? Would an 8T motor suffice? Or am I being too ambitious and need to look towards the 12T motor and perhaps a battery with a higher current-delivery capacity? Am I on the wrong path entirely, and need to be looking at something like the FalconEV system? Are gear-reduced motors in general not all they're cracked up to be? (I've never ridden one.)

I hesitate to say things like "money is no object," however I'm certainly not inclined to cheap out at this stage, as I'd prefer bike #2 to last me a while.

[chroot]

You will happy with Paul (Cell_Man) MAC geared hub motor 12T is pretty slow wind motor and 12T is great for slope hilly without getting stall or overheat the motor. For example 8T and 12T at 48v speed about 30mph (8T) vs 15-18mph (12T) that is my estimate. I have 10T direct drive motor Magic Pie III with internal controller built-in is piece of junk and even cannot handle 10% grade hill as solo 180lbs myself. For being towing a 200lb coffee-roasting trailer and 12T will do excellent job with any slope hilly without getting a stall or hard pedal.

8T is more faster speeding at 5% grade hill, a flat road and it will slow you down at 10-15% grade hill about 12-13mph or less.

Cell_Man is superb excellent reputation!

2 folks o00scorpion00o and neptronix are best guy to ask these question relate MAC geared motors. They mentioned they able climb up hill 10% grade using 8T at 30mph (not sure this is correct info).

[veloman]

If you don't want to go above 25mph, get the 10T. The 8T will handle the 8-10% grades okay, but there's no need for the extra speed (30mph) on 48v, if you only want 25mph top speed. Better to have that extra torque.

And I can guarantee you that you will be blown away how much faster off the line and up hills these geared Mac motors are than a basic DD on the same 'commuter power' of around 1000w.

Cellman is completely legit and a good businessman. He's from Britain I believe, so not what I would call a typical 'Chinese company'.

[neptronix]

cell_man is indeed from the UK.. a white dude doing business out of China.. speaks english.. provides great service.. provides replacement parts.. understands his products very well.. and his prices are comparable or maybe even a lower than his Chinese counterparts.

I forget how many orders i have with him, but i pretty much won't buy from anyone else these days.

The MACs are good motors.. an 8T on a larger 36v ( 15, 20AH ) battery makes for a fantastic commuter, and yes they do have a good amount of extra pep over something like a MXUS/9C DD motor.

[o00scorpion00o]

Basically you are on the right track, and Chroot and Veloman are correct!

If the object is getting up that 15% grade then the 10-12 T is better, The 8T sure is a brilliant motor capable of incredible power for it's size!

Indeed I've got up 10% grades at 28-30 mph on 48 volts, the motor was hot, so I don't know how far or how long it would go for. But heat never caused me any problems, even a 35-40 mph blast for 12 miles never got it hot

So I would recommend the 10-12T just make sure you know the speed it will go on 48 volts before you decide, I think the 12T has a max of 20 mph on 48 volts but would run the coolest up the hill.

cell-man is the best person to ask about how much power to run when you will be climbing steep hills, 15% is steep, maybe ask him to install a temp sensor so you can monitor it, I highly advise that, it's the only way to know if you are pushing it too far.

There are new clutches on the way, though you might have to wait a while. They can fail. Mine did by running far more power than I should have been!

The battery is also a good choice, though you might find 11.5ah a little on the low side if you are riding up a lot of hills, depending on how much you are willing to pedal, and how far you have to go!

I can also say cell-man (Paul) is a great person to deal with, he might take a few days to reply as he is very busy. He is very helpful person and patient!

[dogman]

You can trust Cellman. Occasionally he dissapears for a few days and you get panicky threads from guys in a hurry. But he'll get you what you need at a good price, with good english CS if it's needed.

I'm not quite sure where you are headed with this upgrade, but if 72v is possible, you might want to look at a 2810 rear 9 continent, but run at 72v 20 amps. You'll have about 30 mph, but not so many amps you fry it. It will make your hills seem flat, and no clutches or gears.

But in fact, a 72v 20 amp controller on your existing motor might make you very happy. You won't be crazy fast, but fast when it would fit your needs, like approaching those steeper hills.

If your battery can handle it, just upgrading your existing voltage to 40 amps will perk up the hill climbs too. Nothing you are doing requires special stuff unless it's a really long 15% grade.

Your real reality check is this. Upgrade your bike first. Get a nice full suspension frame, or complete bike if possible on the used market. It doesn't have to be a DH monster bike. Just a decent suspension bike with a fork better than a cheap pogo stick. The bike might cost more than you planned for a choice one, so you might need to ride your existing kit another season.

The good bike will improve your commute much much much more than a different motor.

But if you are now running 36v, 48v would help a lot on those hills. Replacing just the motor with a Mac 10t or the 2810 9c would get you up those hills better, but you will not hit your target speed of 25 mph unless you run more than 48v with the slower motors.

[veloman]

Regarding motor temperatures, I see very little mentioned about ambient temperature. It makes a pretty big difference, even 65 vs 85 degrees F. If I run my 8T Mac at full speed on 1200watts on fast roads, it won't get warm at 65 degrees temp outside for at least 10 miles. If it's 85+, then the motor can't shed it's heat nearly as well.

So, your climate has a big influence on how much you can push your motor too. Although, at ~1000w, I'm told then handle it fine even in hot weather. Lots of variables though. LOTS.

[Joe Perez]

Thanks for all the quick responses, everyone.

If you don't want to go above 25mph, get the 10T. The 8T will handle the 8-10% grades okay, but there's no need for the extra speed (30mph) on 48v, if you only want 25mph top speed. Better to have that extra torque.

And I can guarantee you that you will be blown away how much faster off the line and up hills these geared Mac motors are than a basic DD on the same 'commuter power' of around 1000w.

I'm perhaps slightly atypical on this particular forum in that I'm not planning to turn this bicycle into a motorcycle. For me, the whole point of transitioning to bicycle commuting isn't to save money or satisfy some notion of ecology, it's simply to force myself to get some damn exercise on a daily basis. So I'm not looking to have the bike do everything for me, I just need it to be able to act as a force multiplier and allow me to crest some of these inclines without giving myself a stroke in the process.

There are new clutches on the way, though you might have to wait a while. They can fail. Mine did by running far more power than I should have been!

Well, I'm a realist and I understand that mechanical parts wear out even under the best of circumstances. The one thing that kind of bothered me just from looking at the emissions-free.com website is that there's no mention of spare parts availability. Granted, the motor/wheel kits are cheap enough that I could just order two and keep a spare on hand, but I'd feel a lot better knowing that common service parts are available.

The battery is also a good choice, though you might find 11.5ah a little on the low side if you are riding up a lot of hills, depending on how much you are willing to pedal, and how far you have to go!

I don't think that range will be a problem, assuming that the new system is not significantly less efficient from what I've been running. The 36v 10Ah LiMn battery that Amped sells has historically been sufficient for my range needs, as I do try to do most of the pedaling myself, using the electric assist only as needed.

My primary concern in mentioning the battery was in whether the 11.5Ah battery using a 30A-rated BMS would be sufficient for a controller operating at 30A. In other words, am I likely to damage the battery or BMS by subjecting it to a continuous 30 amp discharge? (see next section of message for why I am particularly sensitive to this concern.) It's well within the specified c-rating of the cell themselves, and assuming that This is the BMS used in that pack, I believe that the notation of it having a "50-80A Protection Current Rating" means that there will be a sufficient margin of safety (and I'd likely fuse it at 35-40A anyway), I just wanted to ensure that this specific area was not a cause for concern.

But in fact, a 72v 20 amp controller on your existing motor might make you very happy. You won't be crazy fast, but fast when it would fit your needs, like approaching those steeper hills.

If your battery can handle it, just upgrading your existing voltage to 40 amps will perk up the hill climbs too. Nothing you are doing requires special stuff unless it's a really long 15% grade.

Well, that's part of the problem I'm having with the system I have now.

I purchased the Amped system as a complete kit, and it came with a 22A controller. I've confirmed with a shunt ammeter that it draws 22-24A (depending on RPM) when operating at full-throttle and high load. Unfortunately, it turns out that the lithium "Tube" battery that comes as part of that kit isn't suitable for use at 22 amps, at least, not the ones they're shipping presently. (I understand that there was a change made after the Tsunami last year which wiped out their primary cell supplier, and that some other changes were made to the design at this time.) The BMS exploded once last September, and then again this past week. Their suggestion after the most recent failure is that I send the battery back for repair (again) and also downgrade to a 15A controller to prevent this from happening in the future. Decreasing the system current from 22A to 15A would render it useless for my application, so as the battery and controller together comprise the bulk of the cost of the system, I've decided that I'm best served just starting fresh with a completely new system.

Your real reality check is this. Upgrade your bike first. Get a nice full suspension frame, or complete bike if possible on the used market. It doesn't have to be a DH monster bike. Just a decent suspension bike with a fork better than a cheap pogo stick. The bike might cost more than you planned for a choice one, so you might need to ride your existing kit another season.

Like I said, money isn't a huge concern here. I'd far rather spend $1k on a nice bike and another $1k on a proper drive system and have something that I really like than go half-arsed just to save a few bucks. And, as I mentioned above, the current drive system isn't operational at the moment to begin with. I'd been contemplating upgrading the bike for some time, and the recent loss of the drive system is what really gave me the motivation to just go ahead and jump.

Replacing just the motor with a Mac 10t or the 2810 9c would get you up those hills better, but you will not hit your target speed of 25 mph unless you run more than 48v with the slower motors.

Don't take any MPH figures I've quoted as etched-in-stone. I put that out there in the first post because I knew if I didn't that would be the first question asked, but I hate giving numbers such as this because then some people might start interpreting them as hard-and-fast requirements. Given that the primary power source under normal operation (particularly on the flat and downhill) is me, and that I'm expecting the motor to really strut its stuff on the hard climbs, I'm far less interested in meeting any specific speed target than I am satisfying the "must be able to climb a 15% grade for 100 yards without stalling / lugging / overheating / exploding" target.

It would be nice if it were fast (I very much enjoy being able to pass the more serious-looking Armstrong Jr's on the uphill sections) however it would be devastating if I wound up with something that was very fast on the flat sections and yet unable to scale the hills that I really need it for. So if a 10T motor is ballsy enough for the climbs, then I'd pick it over a 12T. But if a 12T is what I really need to make the hills without destroying the motor / controller / battery, I'll gladly sacrifice top-end speed for that.

[o00scorpion00o]

Regarding motor temperatures, I see very little mentioned about ambient temperature. It makes a pretty big difference, even 65 vs 85 degrees F. If I run my 8T Mac at full speed on 1200watts on fast roads, it won't get warm at 65 degrees temp outside for at least 10 miles. If it's 85+, then the motor can't shed it's heat nearly as well.

So, your climate has a big influence on how much you can push your motor too. Although, at ~1000w, I'm told then handle it fine even in hot weather. Lots of variables though. LOTS.

Indeed that's why I suggest a temperature sensor.

It's never a problem here really, average summer temp is about 57-64F with the odd day it it might go to 77F so it's really mega hills that will be a problem for me with the 8T mac.

When you think about it, a sensor worth a few cent is all it takes to protect your 400+ euro motor, every motor should come with one, that's why my mac is getting one!

[Joe Perez]

Regarding motor temperatures, I see very little mentioned about ambient temperature. It makes a pretty big difference, even 65 vs 85 degrees F.

I wouldn't have thought that such a small change in ambient temperature would make such a large difference.

Since we're on the Pacific coast, the temperatures are fairly moderate. My morning commute (heading towards the mountain range) is more rigorous than the afternoon return, and temperatures at that time of day are typically in the 60s - 70s. Coming back in the afternoon it can sometimes get into the 80s, however that side of the commute is not nearly as tough, with only a couple of short uphill sections.

Internal temperature monitoring was mentioned earlier (edit: and again while I was typing this.) I assume that this involves threading a thermocouple into the axle and gluing it to the stator somewhere?

[o00scorpion00o]

You won't have any problem getting parts From Cell-Man!

Maybe e- mail him and have a chat, but get everything you need to say in one e-mail as it can take him a while to reply!

[chroot]

I am support o00scorpion00o's suggest because he had push hard on 8T MAC geared motor limitation. The 12T MAC will not get you overheat on hilly that's promise! I would suggest you consult with Paul (Cell_Man) before you are going purchase from him.

I rode ilia brouk (ebikessf), His surly big dummy equipped 12T BMC geared mac simiar MAC design and He live in San Francisco and He climb up nearly 31% grade hill during the test. He able climb completely over the hills.

Here another MAC 10T tested by Hightekbikes at 20% grade hill in SF so 12T will be more faster climb up the hill at ease than on 10T MAC. Here the video show

[GMUseless]

Cell Man ( http://www.emissions-free.com )is certainly reputable and you can be confident in your purchase with him. Don't lump him into the Alibaba world.

The MACs are really fantastic commuter motors. They don't get as much hype as the larger hub monsters, but they are solid commuting work horses. The only downside is the either slow or expensive shipping from China. The 6T full kit (without batteries) I ordered from him ran around $85 shipping SAL....which took about 3 weeks IIRC. Express Air was almost double that. But if it's a MAC you want...Cell Man is the guy to get it from.

If you are staying under 60V, you really don't need the 4110 fets...the 3077s will run better (less heat) at that voltage....and they cost less.

It's also worth mentioning that Methods has 9c 2810's in stock in all sorts of configurations...all for dirt cheap ($100-$150), especially considering the recent hike in magnet prices: http://www.methTek.com Plus, much like Justin at Ebikes.ca, Methods puts much of his revenue back into eBike development.

[o00scorpion00o]

My primary concern in mentioning the battery was in whether the 11.5Ah battery using a 30A-rated BMS would be sufficient for a controller operating at 30A. In other words, am I likely to damage the battery or BMS by subjecting it to a continuous 30 amp discharge? (see next section of message for why I am particularly sensitive to this concern.) It's well within the specified c-rating of the cell themselves, and assuming that This is the BMS used in that pack, I believe that the notation of it having a "50-80A Protection Current Rating" means that there will be a sufficient margin of safety (and I'd likely fuse it at 35-40A anyway), I just wanted to ensure that this specific area was not a cause for concern.

Cell-man is the best person to ask that, he supplies higher rated bms's maybe it would be worth it to get that ? I would have thought it better not to run components at their max specs for long. As far as the cells are concerned, they are rated for 70C continuous, so 30 amps on the pack that would be just under 3C at 30 amps, maybe 4-5C peak. So your pack would have a very easy life! cell-mans triangle battery and bag might be worth the extra money if your triangle can take it ?

How would you feel about LiPo ? IF you don't know much about it I would stay clear, but the reason I asked is because the 12T would probably give you only 15 mph on 48 volts, so I would go with 60 volts. It's far better to have the top speed if and when you need it or want it. It still might only give you 25 mph max and LiPo you can easily configure to the voltage you want, or higher capacity less voltage if you want more range, but you will still have the same w/hrs in the pack, so by just going slower you will have the same range.

You could always ask cell-man if he can make you a 60 volt battery. I would definitely go with 60 volts minimum on the 12T. The other good thing about lipo is the new Zippy compact from Hobby King is far lighter and smaller than LiFePo4, but the LiFeP04 pack would probably last a lot longer, no one knows yet what chemistry the new Zippy compact is or how long it will last!

The other thing about the 10-12T is how fast will it actually go up the hill is what you need to ask cell-man or someone who actually has those motors, you might find that 48 volts is awful slow while climbing!

It would be nice if it were fast (I very much enjoy being able to pass the more serious-looking Armstrong Jr's on the uphill sections) however it would be devastating if I wound up with something that was very fast on the flat sections and yet unable to scale the hills that I really need it for. So if a 10T motor is ballsy enough for the climbs, then I'd pick it over a 12T. But if a 12T is what I really need to make the hills without destroying the motor / controller / battery, I'll gladly sacrifice top-end speed for that.

The 12T would run the coolest, and also be the slowest, It's always better to volt up a slower high torque motor than to run a fast motor with lots of amps, it just means a bigger battery for the extra volts. That's why the 8T is brilliant for me because I like my battery to be light as possible because I like to pedal to keep fit, it also gives me the speed I need for fun and can climb steep hills when I need to and the temp sensor will allow me to find the limits of the motor without killing it. I don't know yet how much of a hill it will climb and for how long!

But if I lived in a very hilly area I would go with the 10-12T and run maybe 100 volts and 30 amps through it to get the speed I want for level ground. It would just mean I need a bigger battery!

From cell-man's website

"Expect approximately 32kph, 20mph on 36V 12S LiFePO4, 40kph, 25mph on 48V 16S LiFePO4, 50kph, 31mph on 60V, 20S LiFePO4 with a 10T 500W Mac fitted into a 26" wheel. There is also a slower wound version, 12T 200rpm loaded at 36V motor which will offer reduced speed for a given voltage with the potential for higher torque. Kits are also available with 700C, 20" and 24" as required."

So I would expect a max of 25 mph with the 12T on 60 volts, and 18-20 max on 48 volts. So that's what you have to decide. You also got to think about how much it will slow down on a steep hill, that I can't answer, ask cell-man.

[Lebowski]

all this 8T, 10T, 12T.... it's all the same motor the only difference is the amount of voltage it makes
for a certain speed. The 12T will be capable of the same speeds as the 8T, it just needs 1.5 times the
voltage to do so.
If you want speed and hill climbing, get a 12T and a 80 to 100V battery.

[dogman]

Very true. Most of the people I have steered towards the 2810 9 continent are running them at 72v, and very happy with 30 mph top speed. And even happier when they have a steep hill to climb. But if you run that motor on 48v, it's too slow for most people, at 19-20 mph. It definitely will climb 15% without any problems, even on a lame 48v 20 amps.

I didn't catch on that your current bike is not running, and now that I know you have the 10 ah bottle battery, you do indeed need to consider a battery upgrade. Cellmans A123 if you prize convenience and safer charging. But if you want a bike that flies, I'd say overclock a 9c 2810. At 72v 30 amps, you'd have a perfect bike that climbs great, and has 30 mph when you need it.

On the other hand, in your climate, I would have no worries about running a Mac pretty hard either. Sure, it gets hotter just a few miles inland, and hot everywhere when you get santa annas, but most of the time your weather is what I'd call ebike ideal.

The advice about making a really good bike the first priority remains. The rest is an easy solve, the only problem is deciding which slower winding motor to choose, and what voltage to run. Just to throw another wrench in the works, if you can get a 2808 from Grin, that would climb 15% a bit better than your current motor, perhaps even on 48v. If you want to stay at 48v, I wouldn't go to the 2810, or the 12t. At 48v, I would say try the 10t at most.

[o00scorpion00o]

I would have thought the Magic pie external controller would climb far better than any 9c?

[Joe Perez]

Wow. Again, I really appreciate everyone taking the time to share their experiences here.

A few people have mentioned various direct-drive motors by referring to part numbers in the format of "2810" and so forth. I do understand what this system of measurement means (width x windings) but one thing I've always wondered, and never been able to get an answer on, is what the equivalent size of the Amped direct-drive motor is, as that's my only real-world basis for comparison in such matters...

Here another MAC 10T tested by Hightekbikes at 20% grade hill in SF so 12T will be more faster climb up the hill at ease than on 10T MAC. Here the video show

Chroot, this video is the single most convincing thing I have seen thus far. That is actually similar to the area in which I live, although our hills are not quite as severe. If a 10T motor can climb that incline on 48v at 1,5kw (which would make it a 30A current draw) then I suspect this is probably the motor / controller combination which I need. Thank you.

If you are staying under 60V, you really don't need the 4110 fets...the 3077s will run better (less heat) at that voltage....and they cost less.

Well, I'd like to leave my options open for the future. And, to be honest, the difference in efficiency between the 4110 and the 3077 should be so trivial as to be immeasurable.

Looking at the International Rectifier's datasheets for the two devices, the 3077 has a maximum steady-state RDS(on) of 3.3mΩ as compared to 4.5mΩ for the 4110, and the VDS / ID and recovery curves appear virtually identical. So if we assume a constant 30A load, then in a worst-case scenario the 4110 would dissipate 4.05 watts at a forward drop of 0.135 volts vs the 3077 at 2.95 watts at 0.099 volts. (Granted, current in a polyphase inverter is not steady-state, however I assume that the operating frequency of the device is so low as to be functionally indistinguishable from DC to a device whose rise and fall times are well under 100ns, and whose dynamic properties are specified in the Mhz range.)

I think I can live with 1.1 watts and 0.036 volts.

cell-mans triangle battery and bag might be worth the extra money if your triangle can take it ?

Huh, I didn't even realized he offered one. I planned to take the measurements of the triangle battery with me when frame-shopping, however. Worst-case I can always go with a rectangular pack and hang it off the front tree or beneath the rear cargo basket.

How would you feel about LiPo ? IF you don't know much about it I would stay clear, but the reason I asked is because the 12T would probably give you only 15 mph on 48 volts, so I would go with 60 volts.

Well, I have no first-hand experience with it, as I've never been an R/C enthusiast. My knowledge of LiPo basically consists of:

• Single-cell prismatic LiPo batteries in consumer devices (eg: cell phones) tend to be reliable at extremely low c-rates.
• Multi-cell LiPo packs sold to the hobbyist community tend to be of variable quality, burst into flames occasionally, and scare me.

Given the relatively good availability of LiFe battery packs, I'm not really considering LiPo.

The other thing about the 10-12T is how fast will it actually go up the hill is what you need to ask cell-man or someone who actually has those motors, you might find that 48 volts is awful slow while climbing!

Well, the video that chroot posted on that subject seems fairly convincing, assuming that the data presented in it is true.

I would also tend to assume that, should I wish to increase the battery voltage at some point in the future, that there's no reason why I could not install a 36v battery pack of equivalent Ah rating in series with the main battery. I'd have to check out the BMSes to ensure that there are no components in them with an inadequate voltage rating. Perhaps this is something I will ask cell_man about directly.

If you want speed and hill climbing, get a 12T and a 80 to 100V battery.

Something to consider for sure. I'm not sure what the single-block BMS options for such a battery would be- I need to figure out with certainty if the series-BMS idea is valid. Two 39V packs in series would really be something.

Very true. Most of the people I have steered towards the 2810 9 continent are running them at 72v, and very happy with 30 mph top speed. And even happier when they have a steep hill to climb. But if you run that motor on 48v, it's too slow for most people, at 19-20 mph. It definitely will climb 15% without any problems, even on a lame 48v 20 amps.

To be honest, I've been leaning in the direction of a geared motor for other reasons as well, principally weight and free-wheel ability. I just didn't realize that there were such capable geared motors out there, given that most of the ones I'd seen previously tend to carry rather small wattage ratings.

And like I said- speed on electric-only mode is not a high priority in this build. If I can cruise comfortably along a 5% grade at 20-25 MPH with a 50/50 split of pedal power and the electric wind, that would suit me just fine. My only concern for speed on the more severe hills (which tend to be relatively short in length, no more than 100-200 meters typically) is that the system be capable of actually getting up them without stalling or slowing down so much that the motor overheats. That's the big problem I had with the Amped system.

The advice about making a really good bike the first priority remains. The rest is an easy solve, the only problem is deciding which slower winding motor to choose, and what voltage to run.

Interesting that you say this, as I've finding the problem to be quite the opposite. There are a number of good bike shops in my area, so it's easy to browse around, sit on bikes, ride them, operate the controls, and get a feel for how they work. (For instance, I rode a bike with disc brakes for the first time this past Monday at one local shop, and I'm absolutely hooked. I'd have never imagined the difference vs. linear-pull rim brakes could be so dramatic!)

By comparison, all I have to go on for selecting a motor and battery is what I can read online. No ability to go into a shop and test-drive them, so it's a much more vexing problem, at least for me, given my present level of (in) experience with them.

[GMUseless]

If you are staying under 60V, you really don't need the 4110 fets...the 3077s will run better (less heat) at that voltage....and they cost less.

Well, I'd like to leave my options open for the future. And, to be honest, the difference in efficiency between the 4110 and the 3077 should be so trivial as to be immeasurable.

Looking at the International Rectifier's datasheets for the two devices, the 3077 has a maximum steady-state RDS(on) of 3.3mΩ as compared to 4.5mΩ for the 4110, and the VDS / ID and recovery curves appear virtually identical. So if we assume a constant 30A load, then in a worst-case scenario the 4110 would dissipate 4.05 watts at a forward drop of 0.135 volts vs the 3077 at 2.95 watts at 0.099 volts. (Granted, current in a polyphase inverter is not steady-state, however I assume that the operating frequency of the device is so low as to be functionally indistinguishable from DC to a device whose rise and fall times are well under 100ns, and whose dynamic properties are specified in the Mhz range.)

I think I can live with 1.1 watts and 0.036 volts.

OK, I've got to admint I haven't done the math on this one (like you did!) I was re-stating what seems to be the conventional wisdom here posted by many of the gurus...such as: viewtopic.php?f=31&t=19587#p357997 and http://www.endless-sphere.com/forums/vi ... 45#p142287

I'll have to do my homework on this one... After reviewing the data sheets ( http://www.irf.com/product-info/datashe ... 077pbf.pdf And http://www.irf.com/product-info/datashe ... 110pbf.pdf) I tend to agree with you. But surely there's some real world sensible difference in heat generation that's perpetuated this concensus?

[Joe Perez]

OK, I've got to admint I haven't done the math on this one (like you did!) I was re-stating what seems to be the conventional wisdom here posted by many of the gurus...such as: viewtopic.php?f=31&t=19587#p357997 and http://www.endless-sphere.com/forums/vi ... 45#p142287

I understand completely.

It's been my experience that information such as this tends to develop a life of its own among people who are not experts in any given subject matter, not just in the e-bike world but within the whole DIY / aftermarket community in general. I'm a forum moderator at MiataTurbo.net, and also a reasonably accomplished amateur engine tuner and ECU builder, so I see things like this all the time whenever people are talking about electronics, thermodynamics, the physics of automotive suspension systems, etc. I specialize in the Megasquirt family of ECUs and have built many of them, the most recent of which I built for myself completely from scratch on a breadboard:




At any rate, even though my day job is mostly digital and small-signal stuff, and don't have much first-hand experience with high power electronics, batteries or magnetics, when it comes to semiconductors, the basics are all the same. Going from the first post you linked to, Jeremy is indeed correct in that the 4410 will have 25% higher loss than the 3077, but what he doesn't make clear is that the actual magnitude of the loss being discussed is so minute as to be almost immeasurable. In the second post you linked to, he does mention that even operating in a region with 10 watts of waste energy, the actual amount of power we're dealing with is trivial compared to both the total energy being consumed in the system (far less than 1%) as well as to the capacity of the 4410 in the TO-220 package to dissipate heat when attached to a simple heatsink without forced cooling.

So yes, one can calculate the difference in waste energy between the two. But the amount of energy being wasted even in a worst-case scenario will neither significantly impact range, nor performance, nor cause damage to the controller.

[pwbset]

I specialize in the Megasquirt family of ECUs

I sometimes dream of ditching my single Solex progressive carb in my '72 VW bus and throwing an FI megasquirt system in there as others have done. *sigh* Too over my head for now I'm afraid.

[Joe Perez]

Well, on the plus side I managed to locate the answer to one of my own questions. Cell_man recently posted a datasheet Here which gives some good data on the battery packs, and also clarifies that the "standard" BMS is suitable for 30-50A continuous discharge, as well as denoting that he has access to 20S and 24S BMSes.

Hmmm...

[GMUseless]

Thanks Joe. From your first reply, I indeed assumed the magnitude of the losses (though 25%) must be quite small. But what isn't quite small is the amount of heat generated from these controllers. That's indeed quite sensible. And at face value, you'd think 25% of that would also be significant. That's why I indicated I really need to sit down and get a handle on the thermal dynamics of the system as a whole.

[Joe Perez]

I sometimes dream of ditching my single Solex progressive carb in my '72 VW bus and throwing an FI megasquirt system in there as others have done. *sigh* Too over my head for now I'm afraid.

To be quite honest, building a fuel injection system isn't as hard as some people make it out to be. The actual wiring and tuning is extremely straightforward- the only challenges you'd face in converting an engine that was originally carbureted and distributor-based is mostly about hardware; finding or fabricating the correct intake manifolds and injector bosses, arranging a crank-trigger mechanism, etc.

One rather simple option would be to retain the use of the distributor but weld the shaft solid in a mid-point position, such that the mechanical advance mechanism is defeated. You could then replace the points with a Petronix or Comp-u-Fire hall-effect pickup, and use this to drive the ECU's primary timing. The distributor would continue to serve the function of allocating the spark to a particular cylinder, however ignition advance would be computed by the ECU which would then drive the ignition coil directly.

I'm not sure what your options would be for intake manifolds. The '72 had the Type 4 engine in it, right? Those were available with EFI in later years, so maybe you could score a complete package of intake mechanicals (throttle body, plenum, injector mounting hardware, etc) from someone at TheSamba. The distributor-based triggering would limit you to single-channel "batch" injection (all four injectors fire together), to get around this, you'd to either fit a missing-tooth crankwheel or figure out a way to get a 1 pulse-per-cycle signal off of the distributor, the cam, etc.

[Joe Perez]

Thanks Joe. From your first reply, I indeed assumed the magnitude of the losses (though 25%) must be quite small. But what isn't quite small is the amount of heat generated from these controllers. That's indeed quite sensible. And at face value, you'd think 25% of that would also be significant.

Well, think of it this way. As you add weight to your bicycle, it requires more energy to push up a hill, so you need more battery current and more motor power. I think we're all on board with that.

The losses which we are dealing with here would be like the weight difference between carrying four golf balls in your pocket as you ride the bike bike versus adding a fifth golf ball. (I'm assuming that you have large pockets.) It's true that five golf balls weigh 25% more than four golf balls, but the total weight of five golf balls as compared to the weight of the bike and rider is laughable.


It's also important that what feels warm to the hand and what actually constitutes a dangerous operating condition for a large semiconductor are two very different things. A '4110 FET is rated to dissipate a maximum 370 watts and operate with a max junction temperature of 175°C (347°F). It also has a combined thermal resistance of less than 1°C per watt (junction to case and case to heatsink), so assuming a proper heatsink connection, we can infer that even at 10 watts of loss (which is worse than worst-case at 30A), the junction itself will be humming along at only 9°C higher than the temperature of the case, on average. So until you reach the point where water boils instantly when poured onto the outside of the controller, I wouldn't worry too much.