New To E-Bikes, Looking for Advice!

[CFinley25]

Greetings Programs!

I've been lurking for a few days and have been youtubing E-bikes for a few days longer. A lot of what I have read is still gibberish to me, keep it simple for me Please. I plan to use this topic as a Q/A page and then later after the refinement a Build page. I will also update this post with the refinements for new people reading and joining the conversation.

Im liking the RC conversions for their simplicity as far as the electronics go, But Im not sure whether it will support pulling the bike (43lbs), myself (235lbs), kids trailer (27lbs), and two kids (70lbs total), So in total a 375lbs. So Im open to suggestions on what would be the more powerful and efficient setup. The trips are pretty short only about 1.2 miles one way, 5 miles total all day plus any mid day spur of the moment errands to walmart or autozone, so Im not looking for a huge amount of range under load, maybe 10-15 max. As for speed under load, I am content with 15-20 mph. Also the route I travel has a 105ft climb over 1.2 miles, I think at its steepest its maybe a 4% grade for a few hundred feet.

Here is what I am looking at right now.
Bike ~ Kingpin 8Ball MTB Bicycle
Trailer ~ Allen Sports Premium Aluminum 2 Child Bicycle Trailer
Motor ~ Looking into either a BBSHD or a 48V 1000W 26" Front/Rear Wheel Electric Bicycle Motor Conversion. Though I am strongly leaning towards the hub motors just for the price, which is allowing me to get the higher Ah lipos.
Batteries ~ Multistar High Capacity 4S 10000mAh Multi-Rotor Lipo Pack
The thought for the lipos was to run 3 packs of 2 wired in Parallel and then have those 3 packs wired together in series, so I should have a total capacity of 20Ah at 44.4v...
For charging all those lipos, I planed to used 2 HobbyKing™ Quattro 4x6S Lithium Polymer Multi Chargers

After some of the replies I feel compelled to let you know I am not a noob when it comes to Lithium Polymer batteries. I have been using them since 2009 and have never had any explode or burst into flames, I have used proper charging, balancing and storage for all of my lipos and still have a few of the first lipos I bought back in 2009.
Please, do not tell me they are unsafe, a pencil is unsafe if you use it incorrectly.

Thank you for all the help.

Chris

 

[wesnewell]

That's <2% grade. Not a problem for even the weakest hub motor. Run one of these on 12s rc lipo for a top speed of ~28 mph. It'll have plenty of power for what you need. 6 of those 4s packs run 12s2p for 10ah will give you ~20 miles at 20 mph.
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=48v1000w%20rear&LH_PrefLoc=1&rt=nc&LH_FS=1

 

[dogman dan]

Oh wow,, sorry if this is a bit harsh, but you need to re think almost everything. I could be wrong, but I'd say forget the RC stuff. I don't know your level of fabricaton skills, but it will work a lot easier for you to just buy a BBs02 mid drive kit.

Nothing wrong with the battery idea,, I run some lipo too, but have to admit that I much prefer to run a lower amps capable bms equipped battery that charges safer when riding bikes that don't need more than 1000w.

I run the lipo on 2000w on up stuff, where I need the c rate. I like 14s,, 48v that you get by combining 5s and 2s packs, or 3s and 4s. Once configured into 7s bundles, you can charge that 7s with a pretty affordable 1s- 8s charger.

Now to the bike,,, the absolutely worst bike you could ever choose, is the roadbastard. Run!!!!

A bargain bike can work, just stay away from the very worst. Get something new or used, that retailed more like $150 new. One with shifters that work, and better brakes. If you can get one with a disc front wheel, that will help, even though you don't plan to ride down to Alameda st. Look for nicer features like trigger shifters, vs cheap twist grips.

If you are going to run a mid drive, be sure you choose a bike with the right type bottom bracket. The really cheap bikes have the larger bb, and one piece steel cranks.

 

[docw009]

Always good to check the user reviews on WMT's online sales pages for possible flaws in a product. Lots of people had the "left crank" fall off on this model, sometimes after exchanging for a replacement bike. Dunno if they meant the arm or the pedal, but one reviewer inferred they used a right hand pedal on the left side? Gee, that would go against 100 years of bike design.

 

[tln]

If you go the mid-drive route: the BBS02/HD will be one of the more expensive parts of the build, but its a really nice system.
I think this might be the way to go since you will want to go pretty slow with the trailer (when you run a hub motor a lot slower than it's
ideal speed, it will start to get hot and you'll be wasting battery / possibly overheat or melt stuff).

Regarding batteries, I think that you should strongly consider a nicer, more convenient and SAFER setup, you don't save THAT much
when you factor in everything. For instance $150 for batteries + $50 for misc parts + $80 for RC charger + $30 for power
supply... so $310... or $399 for http://lunacycle.com/batteries/packs/48v/48v-panasonic-11-5ah-or-13-5ah-shark-pack/ which
will be nicer and SAFER to use every day.

 

[dogman dan]

FWIW, I did not see any bike on the Walmart pages that looked very good for your needs. The sturdy steel beach cruisers all have the wrong crank for use with a mid drive. The others, in my experience, are not very good bikes. You will want good shifters for use with a mid drive, for example. However, it's always possible to start with a cheap bike, and then upgrade stuff like shifters. But if you can, find a better bike for around $100 used, rather than a cheap one new for the same price.

What you need, will be a strong frame. A good aluminum frame, or a steel one. this is because the really cheap alu bikes will have too much flex side to side for that trailer hauling. The tail will wag the dog.

One option is seldom recommended, but is on the table. A beach cruiser and front hub. Why front? I'm talking about the really low price cruisers, which have a coaster brake. In that case, front hub so the bike still has brakes. In the front hub, there are trike kit options out there that are low rpm compared to regular bike motors. In fact,,,, trikes make a darn good trailer hauler. So you could consider a trike too.

But still, mid drive and a good sturdy frame for the win.

 

[wesnewell]

This bike.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=80172&p=1182794&hilit=fortress#p1182072
This hub motor kit.
http://www.ebay.com/itm/48V-1000W-26-Rear-Wheel-Electric-Bicycle-Motor-Conversion-Kit-DIY-US-/252457171543
5ah 12s lipo, <$100
Will get you a top speed of ~28 mph pulling 440 lbs, and have at least a 5 mile range at top speed. Total cost <$400. Will last many trouble free years. I've got over 5 years and 20K miles on my kit just like this one.

 

[Drunkskunk]

We don't sugar coat things here. The motor you picked is rated for 150 amps at 52 volts. That's 10.4 horse power, The same horsepower as a Honda CB125F. No walmart frame, brakes, tires, rims, hubs, etc are going to handle that kind of power.


This:

Will never equal this:

Unless you're an electrical engineer, or have experience working with Lipo batteries, then Lipo are a bad idea. Plenty of members of this forum have lost their bikes, garages, and I think even a house to Lipo fires. They are not safe, and you need a fair understanding of how these things work before you can even evaluate for your self if the risk is worth it. Their best use is in high powered race bikes, and are sort of equivalent of running your car on nitro-methane fuel. If you don't need that kind of power, it's a foolish risk to use it.

Besides, there are batteries out there that are much safer, and cheaper over their lifespan than Lipo, while still being high performance.

From what you describe, you need a high torque, lower speed bike capable of at least 5 miles range.
The good news is that's easy. While a hub motor could do it, you would be better served by a mid drive like a BBSHD.
Batteries are easy enough. a 36v10Ah would far exceed your range needs, but you'll be happier with a52v battery.

As for the bike, you can do much better for the same money. If you're in the U.S., then try Craigslist. there are plenty of forgotten high end bikes being dumped for pennies on the dollar when people realize they don't really want to ride as much as they thought they did. A good Trek, Cannondale, or Specialized can be had often for under $100.
We have a term for Walmart bikes. BSO, Bike Shaped Object. They really are only suitable for hanging extension cords on in the garage.

 

[wesnewell]

I don't need a car that will do 100 mph either, but run at slower speeds puts a lot less stress on the engine. It's the same with electric motors. A 1000W hub motor is capable of over 50+ mph with the right battery and controller. That doesn't mean you have to run it at that speed. Run your car at top speed continuous and the engine will fail pretty quick. Same goes for an electric motor. What I suggested will last pretty much forever even run at 28 mph. Run at only 20 mph, well more than forever. His desired range of only five miles doesn't require much battery, but it still needs to be capable of the max input of the controller. 5ah of rc lipo will produce several times what he needs and will also not stress it. That means it will last a long time. It's the only reasonable choice for such a small capacity battery pack.As for the bikes, I did buy a roadmaster once, and took it back within a week, But the Huffy Fortress 3.0 is solid. I've put my MXUS 3000W motor on it, and even used the rims that cam with it. I normally replace all wheels, handlebars, and seat on ever bike I've bought, and I've gone through more than a few bikes looking for just the right combo for me. He can't go wrong with what I suggested, It will last many trouble free years.

 

[CFinley25]

Thanks for the Reply Wesnewell, I see those are only 48v motors, am I correct in assuming I will need a higher voltage controller or can they handle the 74v as is?

Thank you Dogman Dan, don't worry about it, I came here with an idea and next to no knowledge on the systems so I fully expected what I was thinking to not be a good idea. As far as fabrications skills go, I can use most tools out there except a welder (just never learned how to yet), so making something is pretty easy for me...
I'm definitely interested in the mid drive kits, I've looked at a few websites and a lot of videos but haven't found anything on the torque that these offer. Would these kits be efficient for pulling a 400lbs setup? Is there a specific kit you would recommend or is there only the BBs02 mid drive kit?
Yea, the bike, I looked at a few other sites after making my post and found a lot of other negative reviews. So, I browsed some more and found this one. Kingpin 8Ball MTB Bicycle. While I understand staying away from cheap Wal-Mart bikes, I have never had a problem with them, my last one lasted over 10yrs. But at the same time I don't have the funds or the justification to buy a $200 + bike.
Forgive me but I don't know any of the terms for a bike. What is a BB?
Thanks but I am in no way interested in Beach Cruisers, Im not a fan of the appearance of that style, Mountain, Hybrid and road bikes are really the only types Im interested in...

Thanks for the reply Docw009, Yep I saw that and didn't think much about it, figured I would just throw some thread lock on it, but then I checked a few other sites and apparently there are other problems with the bike to. So provided the sale continues for awhile, I'm looking into Kingpin 8Ball MTB Bicycle

Thank you Tin, While I don't want to go slow, I also don't want to be doing 50mph with two kids in the trailer. I'll definitely check out the BBS02HD, I think it may be the route I end up going...
I have been using lipos for RC and Airsoft since before 2009, ie back when they were dangerous. So I have no qualms with using them or even think that they are unsafe. I do appreciate your input though, that Lunacycle battery does look pretty nice but Im just worried that it paired with what ever system I use, will not provide the power I need to pull 400lbs.

Thanks Wesnewell, I will definitely look into that setup.

Thanks Nelson37, You're correct, most of my time will be around 15mph. Im checking out the simulator now.
As I stated earlier, this will not be my first rodeo with Lipo's I know how to care and maintain them. My hope by using them was to save as much weight as possible because I figured I was either close to or was exceeding the capability of some motors out there.

 

[wesnewell]

Most 48V kits come with controllers limited to 63V max. The kits with displays are usually limited to 60V max. So if you want to run a 20s lipo pack, you'll need a new 72V controller. But the kit will work perfect on 12s lipo. The controllers default lvc will be 42V, which will keep you from over discharging a 12s pack and still allow you to use ~95% of the battery capacity.The motors themselves don't care what voltage you use. I run mine on 24s lipo at 100.8V with a 40A controller. but rarely ever go over 25 mph.

 

[CFinley25]

Unless you're an electrical engineer, or have experience working with Lipo batteries, then Lipo are a bad idea. Plenty of members of this forum have lost their bikes, garages, and I think even a house to Lipo fires. They are not safe, and you need a fair understanding of how these things work before you can even evaluate for your self if the risk is worth it. Their best use is in high powered race bikes, and are sort of equivalent of running your car on nitro-methane fuel. If you don't need that kind of power, it's a foolish risk to use it.

Besides, there are batteries out there that are much safer, and cheaper over their lifespan than Lipo, while still being high performance.

From what you describe, you need a high torque, lower speed bike capable of at least 5 miles range.
The good news is that's easy. While a hub motor could do it, you would be better served by a mid drive like a BBSHD.
Batteries are easy enough. a 36v10Ah would far exceed your range needs, but you'll be happier with a52v battery.

As for the bike, you can do much better for the same money. If you're in the U.S., then try Craigslist. there are plenty of forgotten high end bikes being dumped for pennies on the dollar when people realize they don't really want to ride as much as they thought they did. A good Trek, Cannondale, or Specialized can be had often for under $100.
We have a term for Walmart bikes. BSO, Bike Shaped Object. They really are only suitable for hanging extension cords on in the garage.

DrunkSkunk, I am not new to Lipos, and have been using them since back when they were dangerous, since then they have become a lot more refined and safer to use. The people that cause lipo fires are just idiots, cue the Hover board fires, Yes if you don't properly balance each cell or over charge them or even run them past there safe point, yes you will have problems... I have been using lipos for airsoft since 2009 and yes I still have those lipos and they are still fairly healthy, I don't use them much these days though just because they're big 2.2Ah and I use smaller 1.2Ah lipos...

I don't need a car that will do 100 mph either, but run at slower speeds puts a lot less stress on the engine. It's the same with electric motors. A 1000W hub motor is capable of over 50+ mph with the right battery and controller. That doesn't mean you have to run it at that speed. Run your car at top speed continuous and the engine will fail pretty quick. Same goes for an electric motor. What I suggested will last pretty much forever even run at 28 mph. Run at only 20 mph, well more than forever. His desired range of only five miles doesn't require much battery, but it still needs to be capable of the max input of the controller. 5ah of rc lipo will produce several times what he needs and will also not stress it. That means it will last a long time. It's the only reasonable choice for such a small capacity battery pack.As for the bikes, I did buy a roadmaster once, and took it back within a week, But the Huffy Fortress 3.0 is solid. I've put my MXUS 3000W motor on it, and even used the rims that cam with it. I normally replace all wheels, handlebars, and seat on ever bike I've bought, and I've gone through more than a few bikes looking for just the right combo for me. He can't go wrong with what I suggested, It will last many trouble free years.

Agreed, 30mph top speed is more than enough for me with out the trailer, with it, I don't plan to go over 20... ever... The Huffy you listed was one I actually looked at and considered until I found the Kingpin 8Ball MTB Bicycle. I am definitely looking into your suggestion.

Most 48V kits come with controllers limited to 63V max. The kits with displays are usually limited to 60V max. So if you want to run a 20s lipo pack, you'll need a new 72V controller. But the kit will work perfect on 12s lipo. The controllers default lvc will be 42V, which will keep you from over discharging a 12s pack and still allow you to use ~95% of the battery capacity.The motors themselves don't care what voltage you use. I run mine on 24s lipo at 100.8V with a 40A controller. but rarely ever go over 25 mph.

Ok, makes sense, I'll check it out then.

 

[CFinley25]

Update to what I am looking at right now.
Bike ~ Kingpin 8Ball MTB Bicycle
Trailer ~ Allen Sports Premium Aluminum 2 Child Bicycle Trailer
Motor ~ Looking into either a BBSHD or a 48V 1000W 26" Rear Wheel Electric Bicycle Motor Conversion Kit
Batteries ~ Turnigy 5000mAh 4S1P 14.8v 20C Hardcase Pack or a 48v Panasonic 11.5ah or 13.5ah Shark Pack - The thought for the lipos was to run 3 packs of 2 wired in Parallel and then have those 3 packs wired together in series, so I should have a total capacity of 10Ah at 44.4v...
For charging all those lipos, I was going to copy what jbalatutube's did for his build and use a Battery Management Circuit(BMS) for 12S 44.4V Li-ion/Li-Polymer Battery Packs with a EMC-120 battery charger.

After some of the replies I feel compelled to let you know I am not a noob when it comes to Lithium Polymer batteries. I have been using them since 2009 and have never had any explode or burst into flames, I have used proper charging, balancing and storage for all of my lipos and still have a few of the first lipos I bought back in 2009. Please, do not tell me they are unsafe, a pencil is unsafe if you use it incorrectly.

 

[mark5]

Batteries ~ Turnigy 5000mAh 4S1P 14.8v 20C Hardcase Pack or a 48v Panasonic 11.5ah or 13.5ah Shark Pack - The thought for the lipos was to run 3 packs of 2 wired in Parallel and then have those 3 packs wired together in series, so I should have a total capacity of 30Ah at 44.4v... Right?

How many lipo bricks altogether will you buy? You'll need 18 for 30 Ah.

 

[wesnewell]

Bike looks ok. My only concern would be if it will take 2.4" Cyclops tires. Rim width? Once you run wider rims, you'll never go back to narrower ones. At least I won't.
Stick with rc lipo since you're familiar with it. You'll get much better performance with it.
For 30ah of 12s lipo you'll need 18 5000mah packs wired 12s6p. That would give you a range of ~60 miles at 20 mph. I thought you only needed a 5 mile range. Wire 3 packs in series for ~10 miles at 20 mph.

 

[CFinley25]

How many lipo bricks altogether will you buy? You'll need 18 for 30 Ah.

I was looking at getting 6 Turnigy 5000mAh 4S1P 14.8v 20C Hardcase Pack. You have 2 of these wired in parallel, which will double the Ah from 5Ah to 10Ah, so if I have three of these pairs wired in series to increase its voltage, I go from 10Ah to 30 Ah...

 

[CFinley25]

Bike looks ok. My only concern would be if it will take 2.4" Cyclops tires. Rim width? Once you run wider rims, you'll never go back to narrower ones. At least I won't.
Stick with rc lipo since you're familiar with it. You'll get much better performance with it.
For 30ah of 12s lipo you'll need 18 5000mah packs wired 12s6p. That would give you a range of ~60 miles at 20 mph. I thought you only needed a 5 mile range. Wire 3 packs in series for ~10 miles at 20 mph.

Short of talking to someone that has the bike, Im not finding any other details about it...

 

[mark5]

How many lipo bricks altogether will you buy? You'll need 18 for 30 Ah.

I was looking at getting 6 Turnigy 5000mAh 4S1P 14.8v 20C Hardcase Pack. You have 2 of these wired in parallel, which will double the Ah from 5Ah to 10Ah, so if I have three of these pairs wired in series to increase its voltage, I go from 10Ah to 30 Ah...

Ah only add up when paralleling, not seriesing, so with 6 bricks you'll get 10 Ah. Add batteries in series to get more voltage but not Ah. Add batteries in parallel to get more Ah but not voltage.

 

[_g_]

I have a fairly similar setup.

I bought mine second hand, which cost me £370 (a bit less than it sold for on ebay as the buyer dropped out, so I offered the seller the price minus ebay fees as they wouldn't have to give ebay their tithe.)
That got me a bit better bike, with upgraded brakes (hydraulic discs at both ends), suspension seat post, chunky tyres lighting system (LED strip running lights and twin CREE dual LED headlights), 1k direct drive hub motor with controller and 2x 13ah 6s to run it around 48v along with a couple of balance chargers that were actually better than the ones I already had.

I used it at Glastonbury festival to pull a trailer I made some years ago and normally use with peddle power.

Rather than going with smaller batteries; for a bit more range I'm going to add 2x 20ah 6s batteries from hobby king/ebay. (Seems one of the cheapest ways to get a 48v system per AH)

I won't use it massively and will probably end up losing/damaging/whatever so prefer to spend less now and possibly replace later if needed.

If you're looking to pull weight slower, I'd look to something like a MAC 10t geared hub motor - these will better pull weight at a slower speed.

Mine does ok on my own, but isn't so great with the trailer and Glastonbury mud (I do want to make the trailer self-powered with very high torque motors to cope with the sometimes pretty nasty conditions.)

 

[CFinley25]

How many lipo bricks altogether will you buy? You'll need 18 for 30 Ah.

I was looking at getting 6 Turnigy 5000mAh 4S1P 14.8v 20C Hardcase Pack. You have 2 of these wired in parallel, which will double the Ah from 5Ah to 10Ah, so if I have three of these pairs wired in series to increase its voltage, I go from 10Ah to 30 Ah...

Ah only add up when paralleling, not seriesing, so with 6 bricks you'll get 10 Ah. Add batteries in series to get more voltage but not Ah. Add batteries in parallel to get more Ah but not voltage.

Hahaha, you would think with how many times I looked at the diagrams and had read that, it would have clicked... Thanks for catching that for me, updating the posts...

Rather than going with smaller batteries; for a bit more range I'm going to add 2x 20ah 6s batteries from hobby king/ebay. (Seems one of the cheapest ways to get a 48v system per AH)

If you're looking to pull weight slower, I'd look to something like a MAC 10t geared hub motor - these will better pull weight at a slower speed.

Mine does ok on my own, but isn't so great with the trailer and Glastonbury mud (I do want to make the trailer self-powered with very high torque motors to cope with the sometimes pretty nasty conditions.)

I've thought about running the higher Ah lipos and for now decided against it for now unless I cant get the range I'm looking for I may increase them and get 6 10Ah 4s and pair them the same way.
I'll definitely look into the MAC 10t hub motor.

Whats funny is I have actually thought about making the trailer powered too, thinking this may be a better performer than having the bike pull it, but with how light the trailer loaded is Im afraid it will just spin the tires trying to push me...

 

[CFinley25]

Just finished running through all the motors in the simulator...
Here are the top performers, in order of best to worst, with the parameters set with,
48v 11Ah eZee LiMn, 25AIRFB4110 controller, 26in wheel, Mountain Bike, 440lbs gross weight, and 4% grade.

1. eZee 250rpm - 7.9mi Range, Never Overheating, 18.3mph.
2. MXUS 4506 - 7.9mi Range, Never Overheating, 17.8mph.
3. MXUS 4505 - 7.8mi Range, Never Overheating, 18.1mph
4. eZee 300rpm - 7.8mi Range, Never Overheating, 18.0mph
Tied for 5th.
BMC V2 Trq - 7.6mi Range, Never Overheating, 17.7mph
CLyte TC4080 - 7.6mi Range, Never Overheating, 17.7mph
6. Bafang BPM - 7.5mi Range, 15min till Overheat, 17.3mph
7. Bafang CST - 7.3mi Range, 10min till Overheat, 17.0mph
8. Bafang G02 320rpm - 7.2mi Range, 10min till Overheat, 16.8mph

Thoughts? Any suggestions on a slightly cheaper place to get an eZee 250rpm?
Found it for $720 here... eZee eBike 36V-48V 1000W Conversion Kit - Rear Wheel

 

[wesnewell]

If your figures are correct, that 1.2 mile grade is 1.66%. No where near 4%. Now if you want to spend 5 times as much for that geared motor kit, have at it. Be aware you will not be able to get regen braking and geared motors have clutches and gears that fail. And they are also noisier because of the gears. Good luck.

 

[_g_]

Whats funny is I have actually thought about making the trailer powered too, thinking this may be a better performer than having the bike pull it, but with how light the trailer loaded is Im afraid it will just spin the tires trying to push me...

You can get pusher trailers that are basically just a motor, wheel and battery which are intended to provide external electric oomph, so you don't have to add any of the stuff to your bike. They seem to go ok. It was suggested to me I'd do as well with that sort of setup over making a fancy control system that only applied power when the trailer was pulled.

The MAC motors come in different turns so from 6T to 12T - the highest having the most torque but lowest speed. I'd be looking at two 12T motors for my application - seeing that I can get ok speed in most circumstance with peddle power alone, it's the steep uphills and thick sticky mud where I need the extra shove, so having similar torque to my Mercedes Vito van can't hurt . (Well, until it strips the internal gears anyway!)
Not seen other motors come specified like that, but I've got a lot less knowledge of what's around than many on here.

(Incidentally, I do generally like the idea of mid drives, but for a fairly heavy system it makes it more likely to fail and I've had drive train issues before at Glastonbury - while a hub drive means if one fails the other still works fine.)

 

[CFinley25]

If your figures are correct, that 1.2 mile grade is 1.66%. No where near 4%. Now if you want to spend 5 times as much for that geared motor kit, have at it. Be aware you will not be able to get regen braking and geared motors have clutches and gears that fail. And they are also noisier because of the gears. Good luck.

The route I take is not a gentle continuous 1.66% grade for the whole 1.2miles, its more like 3% for a 1/3rd of a mile, 1% for another 1/3rd, and 4% for the last 1/3rd...
These numbers were from the Ebike simulator, so I doubt they are 100% accurate, which is why I have been asking for your opinions and real world setups.
If the general consensus is that the Bafang BBSHD is the better option for pulling 400lbs up hill with no sweat, then cool, I'll pursue the BBSHD.

Whats funny is I have actually thought about making the trailer powered too, thinking this may be a better performer than having the bike pull it, but with how light the trailer loaded is Im afraid it will just spin the tires trying to push me...

You can get pusher trailers that are basically just a motor, wheel and battery which are intended to provide external electric oomph, so you don't have to add any of the stuff to your bike. They seem to go ok. It was suggested to me I'd do as well with that sort of setup over making a fancy control system that only applied power when the trailer was pulled.

The MAC motors come in different turns so from 6T to 12T - the highest having the most torque but lowest speed. I'd be looking at two 12T motors for my application - seeing that I can get ok speed in most circumstance with peddle power alone, it's the steep uphills and thick sticky mud where I need the extra shove, so having similar torque to my Mercedes Vito van can't hurt . (Well, until it strips the internal gears anyway!)
Not seen other motors come specified like that, but I've got a lot less knowledge of what's around than many on here.

(Incidentally, I do generally like the idea of mid drives, but for a fairly heavy system it makes it more likely to fail and I've had drive train issues before at Glastonbury - while a hub drive means if one fails the other still works fine.)

I might still do this later with a few smaller motors, just to reduce the load for one motor on the bike.

 

[wesnewell]

Even if you whole 1.2 miles were 4%, the cheap 48V 1000W hub motor I listed would not overheat before it got to the top. I've given you the cheapest most reliable option. It will not strain your bike s drive train like a BBS option will. Take it or leave it. It's your time and money.