A Bike for Hikes

[ndk]

Sanity check, for anyone with the time. Will an electric bike work for me?

Scenario: I live near beautiful RMNP. During the summer, I rely on the shuttle buses. They don't run during the winter. I'd like to get to trailheads with most of my energy, but do so in an economical and environmentally friendly manner. Fairly light traffic on the roads, and they're rarely wet, snowy, or icy. Speed limits are generally 25-40 mph on the roads I'd like to traverse. Most have good visibility and good shoulders; nothing above 8% grade, generally 6% or less. I'm 210 lbs. Distance and delta elevation to the best remote trailheads is 11 miles each way, and 1600ft of elevation. Efficiency, brakes and torque are important; speed, less so. The ambient temperature is generally around 30-40 degrees F, but I'd like to use the bike in weather as cold as 10 degrees at times.

This is a very low crime area, but since lots of tourists come through, theft may be an show-stopper. There are no bike racks, but there are plenty of ponderosas. Some of the trailheads have manned ranger stations; others don't.

The bike: I'm looking at a dirt-cheap steel-framed bike as a base. Shocks aren't important since all the roads are high quality and paved, and I don't care about light, fancy components. I want a high-torque, high-efficiency, braindead choice; the Magic Pie II seems like a much-maligned but reasonable one. Power it with an array of LiFePO4 batteries for their cold resistance, maybe 36V/20AH(enough?). I assume gear-driven in the rear wheel is better for the additional torque. Can I mount the batteries on a rear rack, slap on reflectors and a light and call it a ride?

 

[FMB42]

My take would be:

1. Park and lock only at the "manned" Park Ranger Stations.

2. Steel framed hard tailed MTB with a decent (aftermarket ?) disc front brake ( $45 Avid BB 5, etc) .

3. Geared hub motor kit (300-450 watt).

4. 18 - 20 AH 36-48 volt LifePo 1C minimum battery (most LifePos will meet this "C" rating).

5. Removable battery mounted on a heavy duty rear rack (be sure to use a heavy duty rear rack (not a full suspension "seat post" style rack ).

6. Limit use to 20 degrees F or above.

 

[x88x]

6. Limit use to 20 degrees F or above.

I could definitely be wrong about this, but I thought the LiFePO4 chemistry played fine with sub-0 temps discharging, and just required higher temps when charging.

 

[Drunkskunk]

The limiting factor here is going to be the battery. A good LiFePO4 can handle temps down to -20C (-4 F) and if you keep it inside when not in use, and insulated on the bike, it shouldn't get that cold. All batteries have less capacity when cold, but Lithium keep more of it, so you won't be losing too much.

But cold batterys get less range, and you're going to be fighting up a hill, so the batery needs to big. 48V 20A at least. 25A woudl be better. But the bigger, the more mass it will have, so the longer it will take to cool and the better it will preform.
36 volts isn't likely to be sufficent for any hill climbing on anything short of an RC setup.

A geared motor would be ideal... Except I would worry about the brittleness of the gears at very cold conditions and sustained high loads.

A DD hub motor wouldn't be as efficent climbing, but a 500 watt would do the job up a 6 to 8% slope fine. a Nine Continents 6X10 would be ideal.

The Magic Pie would be even better as a motor because of it's high torque design, But it's internal controller with a low voltage rating aren't. It would need to be gutted and modified for an external controller first.

 

[FMB42]

6. Limit use to 20 degrees F or above.

I could definitely be wrong about this, but I thought the LiFePO4 chemistry played fine with sub-0 temps discharging, and just required higher temps when charging.

I'm speaking more in terms of the ill effects (i.e. brittleness, etc) that sub 20 degree F weather can have on certain plastics found on many MTBs, LiFePo4 batteries, and motor kits these days.

Sorry, I should have further explained my opinion on sub 20 degree F weather.

 

[ndk]

First, thank you so much to everyone for your insights. Glad I wasn't too far off base.

The Magic Pie would be even better as a motor because of it's high torque design, But it's internal controller with a low voltage rating aren't. It would need to be gutted and modified for an external controller first.

Could you elaborate on this a little, Drunkskunk? The marketing materials seem to advertise a 48V version that can put out 1000 watts. I'm not interested in having to gut and modify something if I can get away with it.

Battery-wise, I'm looking at Ping's 48v 20w LiFePO4. I'm not sure how I'd insulate it, and it could be sitting outside at 10 to 20 degrees for some time while I hike. But the trip home is basically all downhill.

For the bike itself, would the '10 Diamondback Kalamar LX suffice? Steel frame and geometry that I like, but it might not be sturdy enough. Should/can I use a 6 speed freewheel(presumably necessary to allow room for the motor even though the stock bike has 7 speed shifters? I like the disc front brake suggestion, thanks.

I also called the park to confirm they're cool with this, and they think it's a great project.

 

[torker]

Good on the battery except I would strongly suggest a lockable metal box for it. The battery alone cost about as much as the rest of the bike. If you are truly not worried about speed then go with the slowest wind you can so at 48 v it will be happy lugging along at 10-15 mph. Think 9c 6x10 if you can find it or Crystalyte 409 or 4011 or maybe a slow gearmotor except that I might worry about the hills ruining the gears if you carry you plus pack etc. up them alot.

 

[Drunkskunk]

First, thank you so much to everyone for your insights. Glad I wasn't too far off base.

The Magic Pie would be even better as a motor because of it's high torque design, But it's internal controller with a low voltage rating aren't. It would need to be gutted and modified for an external controller first.

Could you elaborate on this a little, Drunkskunk? The marketing materials seem to advertise a 48V version that can put out 1000 watts. I'm not interested in having to gut and modify something if I can get away with it.

Battery-wise, I'm looking at Ping's 48v 20w LiFePO4. I'm not sure how I'd insulate it, and it could be sitting outside at 10 to 20 degrees for some time while I hike. But the trip home is basically all downhill.

For the bike itself, would the '10 Diamondback Kalamar LX suffice? Steel frame and geometry that I like, but it might not be sturdy enough. Should/can I use a 6 speed freewheel(presumably necessary to allow room for the motor even though the stock bike has 7 speed shifters? I like the disc front brake suggestion, thanks.

I also called the park to confirm they're cool with this, and they think it's a great project.

When Golden motor says it will do 1000 watts, they mean peak. The internal controller is a 20 amp max unit, and there isn't space or sufficent air flow for a bigger unit. 48Volts X 20 amps = 960watts.

For what you want to do, you need a 30A to 40A controller at 48 volts, giving you a peak of 1500 to 2000 watts. Just about any common 500 watt motor can handle that, including the pie, but the controller is the limiting factor.

The Pie is advertised to have 20% more torque that other 500 watt motors. That may be optimistic marketing, but it may be true. It does have more certianly. But the normal motor would be a GM, Aetoma, or Clyte 500 watt. A 9C (Nine continent) has around 10% more torqe than those already.

In addition, Ebikes.ca has some special large diameter 9c (part # M1606R26) that give a little more torque than the standard and may well be similar output or better than the Pie, but with the advanatge od being an external controller type motor.

 

[ndk]

So, I've come down to two options in a similar price range: a Magic Pie with a 36v/20Ah LiFePO4 battery, or this wacky kit off eBay from YXM that seems intriguing on the surface.

http://cgi.ebay.com/1000W-48V-electric-bicycle-bike-Motor-Kit-lifepo4-20AH-/290443810343

There are several posters here who have bought and used the motor or the full kit(a particularly epic diary from Little-Acorn was grand fun to read) but they mostly seem to be interested in top speed. Several people have observed that it appears to be a 9c (or even a GM) motor, but I have no idea which one. Anyone with a guess? There's a spec sheet on one of the posts but I can't translate from its optimal 9-18 Nm efficiency zone to sustained output on that modest incline.

http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=13913&p=239264&hilit=+yxm#p239264

At that price point I'm tempted to get the YXM kit and try it. Worst case scenario I buy a Magic Pie or other motor and use the 1c 48v/20Ah batteries... though those batteries might be too weak for the 30A or 40A controller you're talking about.

EDIT: From the spec sheet, it looks like the KV is on the order of 9.5 rpm/V, which is about the same as the 9c 1606, which should mean ceteris paribus that it's about as torquey and efficient... right?

 

[ndk]

Coming back to say thanks, and to ask a question.

Combining your ideas with the advice of the local retailer, I built the bike around a Magic Pie with the internal controller and a 36V/20AH 1C battery. Way more than fast enough on flats. The regenerative braking is absolutely fantastic coming back downhill. I barely have to use the caliper brakes(disc brake was incompatible with my frame).

The problem comes on the sustained uphill legs. The bike never gives out entirely, but I'm putting out way more torque than the bike at an exciting 6mph, and though I have no ampmeter, I'm sure it's sucking the batteries dry for the creation of plenty of heat.

From what I can tell, one stupid mistake is that I'm using 700C wheels. This of course reduces the number of revolutions per meter traveled, and as such reduces the motor's torque.

It gets me there and back, consuming about 30% of the battery for the ~12 miles. So, the question:

Can I wire this up to a 48V/20AH 1C battery, hand this battery down to my much lighter wife, and sustain enough power density to go these gradients? Or am I better off switching to a mid-drive, which I'd really rather not do? Or should I have the LBS re-lace the hub into a 26" and grab a new frame and rebuild it?

p.s. I'll add the obligatory: "Experts at Endless Sphere were right, and 36V isn't enough." Here's a little photo journal of what I built and where I went, if you'd like to see:

http://www.city-data.com/forum/colorado/1236819-electric-bicycle-rocky-mountain-national-park.html

 

[Rassy]

Sounds like the experience you gained from your first e-bike has prepared you well for your next build. I have a 9C 6X10 at 48V on my trike, but it is a mid-drive through the gears, however, Dogman has reported good climbing on the 6X10 used as a regular hub motor. So short of going mid-drive for your climb, I would consider the 9C 5X12 that Methods currently has for sale. Run at 48V I would expect it to walk right up your hills, and being a DD you could still use your regen going back down. I would expect quite a bit faster than 6 MPH, but you would need to get a good estimate of how fast from another source.

Good luck with anything you decide to do.

 

[amberwolf]

Since speed isn't your concern, but rather hillclimbing torque, then going with a smaller wheel will help that, but it may not increase the speed at which you're climbing any, though it might help out with the motor's load.

Since the MP has a controller built in, all the heat generated by both controller and motor is stuck in there (unless you ventilate the hub as others have done with regular hubmotors). Raising the voltage is going to raise that heat level, too, even if you "gear down" by decreasing your wheel size.

Volting up will most likely help climb the hill better, especially in combination with decreasing wheel diameter; in any regular hub I'd just recommend trying that, but I wanted to point out the heat issue with the MP's built-in controller.


If you had a front motor, you could fairly easily change to a smaller wheel without swapping the whole frame out, as you could just change forks to a longer one (like some shock forks with much longer travel would be), or use one with a longer steerer tube and then use spacers between the top of the crown and the bottom of the headtube, to make up the change in wheel height.

Using the rear motor, you would have to significantly modify the frame you have to keep the same geometry, and possibly move the brake bosses.


Also, just to point out one more thing: With a 1C 20Ah battery you're limited to 20A, and going uphill it's gonna wanna draw a lot more than that. I assume your MP controller is limiting the current at that point, but if you were to use a different motor/controller, it will need to have a current limiter to prevent overtaxing your battery.

 

[ndk]

Sounds like the experience you gained from your first e-bike has prepared you well for your next build.

Definitely. I've been disabused of the notion that I'd get it right the first time around, but I did get it close, which makes me happy. The bad news is, I'm starting to see how this could very quickly turn into a serial obsession. You can always make it better, right? Uh-oh.

I have a 9C 6X10 at 48V on my trike, but it is a mid-drive through the gears, however, Dogman has reported good climbing on the 6X10 used as a regular hub motor. So short of going mid-drive for your climb, I would consider the 9C 5X12 that Methods currently has for sale. Run at 48V I would expect it to walk right up your hills, and being a DD you could still use your regen going back down.

I'm a little jealous! I'd love to have a recumbent trike, but these are very busy roads in the summer with several blind curves, so I'm too worried about being low-profile and low-visibility.

Checking Alan B's totally amazing spreadsheet in that thread, it looks like a 5x12 would be expected to top out ~20mph with 48v supplied to a 700C wheel. That's quite a bit torquier than the Magic Pie. Hooking one of those, or even a 6x10, up to 48v would almost certainly do the trick. It's really not far from the performance I need already, maybe just 3-4% grade off. It seems that getting a 48V/20AH battery, trying it with the Magic Pie, and then buying a slow wound 9C motor if it's still insufficient is the way to go.

Since the MP has a controller built in, all the heat generated by both controller and motor is stuck in there (unless you ventilate the hub as others have done with regular hubmotors). Raising the voltage is going to raise that heat level, too, even if you "gear down" by decreasing your wheel size.

I don't know whether heat is becoming an issue yet or not. My guess is that riding for between 20-45 minutes and in temperatures around 40-60°, it'd be okay. Goodness knows other people have taken the Magic Pie much further than I have, though probably mostly with external controllers.

Worst likely case scenario, I blow the controller and have to rewire the Magic Pie to a new external controller, yes? (your point about current limitations very well heeded here) Supposedly, the internal controller can just be reprogrammed to handle 48v -- at least, there's a radio button on the software panel for it.

If you had a front motor, you could fairly easily change to a smaller wheel without swapping the whole frame out, as you could just change forks to a longer one (like some shock forks with much longer travel would be), or use one with a longer steerer tube and then use spacers between the top of the crown and the bottom of the headtube, to make up the change in wheel height.

Using the rear motor, you would have to significantly modify the frame you have to keep the same geometry, and possibly move the brake bosses.

It's a rear hub motor in a $200 bike. I'm more than happy to swap frames. But being a lazy human, I'd just like to avoid it if I don't need to and can get away with just swapping the battery.

I'm getting the sense that iterative alteration would work here -- first stepping up the voltage, then switching motors if necessary(still insufficient torque, or too much heat), then switching frames/wheel sizes if necessary(still insufficient torque) would be a fine approach.

But your point about the 1C battery is interesting... would something like a 36V/25AH 2C battery make a substantial difference? More of a difference than 48V/20AH 1C? I'll tell ya, I'm already scared about going any faster on flats. Thank goodness for throttles.

 

[Rassy]

I'm starting to see how this could very quickly turn into a serial obsession. You can always make it better, right? Uh-oh.

Yep, you got it. Most on this forum seem to do multiple builds, and as you stated you may be able to reuse some stuff on a build for your wife, particularly if you use a smaller wheel bike.

You mentioned using a 1C battery. Perhaps some are still 1C, I don't know, but even a Ping V2.5 is rated at 2C continuous and capable of 4C bursts according to his site. I think I saw somewhere that Ping stated even these ratings are conservative for the V2.5.

Edit: I just reread what you said about a larger 36V battery above. The answer is no, you would probably only notice the heavier weight. The only real advantage would be more distance.

 

[ndk]

You mentioned using a 1C battery. Perhaps some are still 1C, I don't know, but even a Ping V2.5 is rated at 2C continuous and capable of 4C bursts according to his site. I think I saw somewhere that Ping stated even these ratings are conservative for the V2.5.

I'm too cheap -- I mean value-oriented -- to buy even a Ping battery. Mine is YXM Zone:

http://stores.ebay.com/YXM-Zone

which claims 1C continuous/2C burst for the 20AH battery I bought:

Rated Discharging Amperage:20A
Max Continuous Discharging: 20A
Maximum Discharging Current:40A

At the price point of these cells, I'm inclined to believe them.

 

[amberwolf]

Mostly if you get a higher C-rate battery (even if it's the same Ah) you can pull more current from it to be able to pull harder with the motor when you need to. Not with the MP, probably, since it should be limiting to 20A anyway, but with external controller or other motor/controller setup, you'd be able to do it if you needed to. Right now, I'd say those specs say it's not recommended.

But even that mostly depends on how long you want the battery to last. Many batteries will do much higher currents than what they are spec'd for, continuously, but they will be damaged by it. Sometimes a little, sometimes a lot, slow, fast, etc., but either way they have a longer life if you don't push them like that.

Often the "max" currents on them are for a few seconds or less, like when starting up from a stop. Doing a hill at higher rates would probably be bad for them.

Some of them have a BMS that cuts out if you sustain higher than some A rating for more than a specified time, just as if the voltage dropped too low.


The iterative approach is often more affordable way to experiment, but it can lead to an addiction, too, and then your ebikes begin to breed. :lol: Eventually you end up with rooms like this:

 

[chrisvw]

Hi ndk,
I assume when you say RMNP you mean Rocky Mtn and you live in/near Estes Park?
I live in Ft. Collins - we have two ebikes you might want to try for comparison to help decide what you ultimately need. My wife's bike is a 9C with a 48V NiMH battery and 20a controller. It has the "speed" winding, not the power windings that others are mentioning. I have a Crystalyte 5303 (also more speed than power) with 48V LiPOs and a 40a controller. If you could make it to Ft. Collins, we could let you try it out on some of the various grades around here.

I've been riding my bike at temps down to 20 degrees. I store the bike in the garage that seldom gets below freezing. I haven't had much trouble with battery capacity at these temps, though I never "store" the bike in sub-zero temps for more than an hour or so.

It seems to me that your limiting factor is may be the C rate of your batteries. I can't overemphasize that when you are pulling "max amps", you should let the controller, not the batteries be the limiting factor.

 

[Raining]

Hi ndk,

I see you are facing similar issue as me see: http://endless-sphere.com/forums/viewtopic.php?f=3&t=24494

Except for your case, you are seeking more torque unlike me (speed). I skim thru your posts and city-data postings, as what the experts says (More Volts/Ah Draw/Smaller wheels is the way to go.

Not sure if you have this item ->

With this you can access->

From my view you have 2 options with regards to adding torque (minimal fuss & cost).

1. Just adjust your current via your PC if you have the GM interface cable posted above (Do note amberwolf's caution on shortening the battery's lifespan though.)

or

2. Add another 12V 20Ah battery(cheap & small) in series bringing your total volts to 48V. I'm assuming you are still using the 36V YXM Zone battery. You can adjust your voltage through the same GM interface.

Hope this helps,
Raining

 

[ndk]

Yep, I live in downtown Estes Park just up the hill from you. I very rarely come down to the Fort -- it's usually Lyons, Boulder, or Denver -- but I'm very thankful for the offer. We should definitely go riding in the park together sometime, if you ever lug your E-bikes up here!

I just bought a 48V/20AH battery from Conhis Motor.

http://conhismotor.com/ProductShow.asp?id=47

Even at 1C that should be (barely) capable of feeding the Magic Pie the 1000W it's rated for at 48V, and it says it discharges continuously at 2C, so I should be set.

Separate noob question: I don't have an amp meter, and I'm trying to gauge how much I discharged the battery by how long it took to charge. I went about 23 miles yesterday and 1200ft of vertical, and it took 2 hours and 5 minutes to charge the 20AH battery back to full, using a 5A fast charger. That would mean I used ~45% of the battery, or about 14 Wh/mile, correct?

If so, I'm really impressed by the efficiency of the Magic Pie.

 

[ndk]

1. Just adjust your current via your PC if you have the GM interface cable posted above (Do note amberwolf's caution on shortening the battery's lifespan though.)

I totally forgot that there was a separate configuration option for amperage. I checked it, and it's already set to 30A continuous and 50A peak(stock I guess, because I don't think I changed it), which is the max. That is a little worrisome, and I might already have been banging on the batteries. I use a BMS system, though, and I guess it would prevent that from happening?

2. Add another 12V 20Ah battery(cheap & small) in series bringing your total volts to 48V. I'm assuming you are still using the 36V YXM Zone battery. You can adjust your voltage through the same GM interface.

This would be the smart and sane approach, instead of buying another battery pack. But I have an excuse. I'm going to be handing down the 36V/20AH to my wife so we can ride together. She weighs 110lbs to my 200lbs, so I think we will go about the same speed and distance if she is 36V/20AH and I am 48V/20AH.

I hope you find the speed you need, Raining! You find 48km/hr slightly disappointing, and I find it quite scary. Good thing we can build our own to match our courage levels.

Take care,
Nate.

 

[Ykick]

If you don't wish to deal with Hobby King for a Turnigy power meter goto epbuddy.com, spend $30 and buy a power meter like this - http://epbuddy.com/index.php?main_page=product_info&cPath=8&products_id=42

Figure out a connector scheme while you're at it because you want to be able to insert a power meter between the battery/motor and battery/charger. You can use the same meter for either but will need to reverse to read current in each direction. I buy my Anderson connectors from Powerwerx.

Battery chargers rarely deliver exact specified power. 5A could be 5A or 4.3A. And battery chargers also taper current off towards the end of charge so going by "time" and "spec" is very, very inaccurate. You might get within 35% of what really transpired but you might not.

My guess is your system actually draws between 20-35wh/mile. My 1000W 48V 22A controller routinely sucks 35wh/mile with very mild pedaling over an 8 mile commute - about 2 miles of bridge approach. 4-6% grade?

Anyway, get a power meter - it's the only way to know and every eBiker who's asking the questions you're asking needs to have one. Afterall, you're already thinking 2nd bike, pretty soon you'll get thinking about what Lipo can do...

 

[ndk]

Anyway, get a power meter - it's the only way to know and every eBiker who's asking the questions you're asking needs to have one. Afterall, you're already thinking 2nd bike, pretty soon you'll get thinking about what Lipo can do...

Yeah, I think it's time. I'll order one now. Thanks for the leads.

All I know about what LiPo can do so far is "catch fire" and I'm forced to park my bike in a rental apartment in a lovely office building in a small town with a volunteer fire department. It's #1 on my to-check-out list as soon as I buy a home and ensure I'm primarily destroying my own property.

 

[Ykick]

All I know about what LiPo can do so far is "catch fire" and I'm forced to park my bike in a rental apartment in a lovely office building in a small town with a volunteer fire department. It's #1 on my to-check-out list as soon as I buy a home and ensure I'm primarily destroying my own property.

Lipo fire is highly over-rated but it is serious stuff much like storing gasoline in a garage or shed would be. Gotta take precautions and treat 'em right but the payoff is quite nice.

My honest and hopefully gentle critique about your bike is the majority of weight sitting over the rear tire. Motor, controller, battery and butt. In my case the later is quite heavy so with Lipo I can carry a LOT of range and distribute that weight between the wheels.

 

[Rassy]

Ykick wrote:

Battery chargers rarely deliver exact specified power.

I've used several 2 amp chargers for LiFePO4 batteries. For all of them the charge time has been almost to the minute what I computed it should be based on the amps used from a Watts-Up meter.

Since it's just extra work to wire up/replug, etc. to measure the amps going into the battery, I would recommend you just keep it simple and measure your usage. Then after a couple of recharge cycles, even if the charger isn't right on 5 amps, you will know the actual output of the charger and can just use that number in the future to estimate the charge time needed. Just my $.02.

 

[ndk]

I've used several 2 amp chargers for LiFePO4 batteries. For all of them the charge time has been almost to the minute what I computed it should be based on the amps used from a Watts-Up meter.

Thanks so much for this anecdote. And, your experience and Ykick's guesstimates/experience are not necessarily incongruous. Many of the miles included in my journey were downhill and completely unassisted. If it pulled 30Wh/mi going up, 15Wh/mi on the flats, and 0Wh/mi on the way home, it would all add up rather nicely. Because this was joyriding, and not on my way to a hike, I was also putting in my small share of human power. :wink:

Since it's just extra work to wire up/replug, etc. to measure the amps going into the battery, I would recommend you just keep it simple and measure your usage. Then after a couple of recharge cycles, even if the charger isn't right on 5 amps, you will know the actual output of the charger and can just use that number in the future to estimate the charge time needed. Just my $.02.

Great idea. That's exactly what I plan to do.