what level of ebike is needed to match my ride today?

[voicecoils]

Match or exceed I should say!

Here are stats from my Garmin Edge 305, great GPS bike computer:

What type of power, and energy storage would be required to do the same ride with no peddling?

In other words, average 28kph over 2hrs, hit max speeds of 55kph or higher, ascend 750 meters with grades up to 13%.

The power and energy storage required would dictate what type of hub motor, battery chemistry (& capacity) and controller would be needed.

 

[voicecoils]

[edit] if your browser is cutting off the image click here to see it in a new window:
http://www.concordski.athena.thinkhost.com/images/sat_ride.jpeg

 

[knoxie]

http://www.kreuzotter.de/english/espeed.htm

 

[knoxie]

You should be able to calc your watts per hour from this, should be able to set a rig to match those specs fairly easily without checking the sums.

Knoxie

 

[voicecoils]

thank you here is a start:

http://www.concordski.athena.thinkhost.com/images/pwr.jpeg

I should do separate calcs for ascending, descending, and flat. My Garmin says I used 2350 calories on the ride, so the above is clearly not a perfect representation. If I could do that ride on an ebike using just 0.36kWh, damn but I think the ebike would use way more, to ascend and to overcome the extra bike weight.

 

[TylerDurden]

13% is steep.

This chart is faster than clicking

You need 1000W to make 24kph uphill, so your system needs to deliver that to the wheel and your pack needs to be big enough to discharge at a rate that won't kill it (based on chemistry).

 

[pwbset]

Wow. If I was in the kind of shape you seem to be in I wouldn't have even bothered getting a motor and all these expensive batteries!

 

[dogman dan]

No kidding., It looks to me like he only needs about half the ebike power, instead of about 90% like me. Seriously, he could do it on my mongoose. That is a cool chart, it matches the performance of my bike perfectly.

 

[huskydave]

Crytalyte x5 running 48v 48a controller and 2 15ah lithium batteries would do it.

 

[voicecoils]

13% is steep. You need 1000W to make 24kph uphill, so your system needs to deliver that to the wheel and your pack needs to be big enough to discharge at a rate that won't kill it (based on chemistry).

@ TylerDurden

That is a handy chart and good advice. Lets say the motor and battery pack are each 80% eff (feel free to correct me) then the pair are 64% efficient, if wiring controller losses take that down to 60% then 1.67kW would be required to be delivered by the batteries.

For that same uphill situation (13% slope, 24kph) the above simulator tells me that the difference in power requirements between a 8.5kg bike (pedal powered) and an 35kg bike (guessing weight w/ ebike kit) is 20.5%. That would bring the power requirement from the battery back up to 2kW, sound reasonable?

@ pwbset and dogman

If you look at my height and weight above I'm overweight That weekly Saturday ride is meant to be strenuous, other rides during the week are more relaxed. I coulden't commute that ride because I'd arrive at my destination needing fresh clothes, a shower, and a nap The real key to keeping pace over such a ride is spandex and a $$$ bike :wink:

@ huskydave

Any Idea what that setup would weigh. From the above calcs, it looks like 48v 48a might do it, thats 2.3kW if the battery pack can sustain that draw. Your suggesting 30ah of lithium at 48v? That's 1.44kWh, which would power me up the hill discussed above for 1.4 hours straight, damn. However, a 15ah rated pack is not likely to be able to provide that amount of energy if 48a is drawn continuously, correct?

Thanks for everyones patience with all my questions and musings.

 

[huskydave]

Well from my knowledge and a lot of mistakes I can accurately give a good picture of the 5304 and 5303 motors. You went quite far and climbed quite high. I know with my 48a controller and 12ah lithium battery running 40v I can go approx 30-35 km with an average speed of 25km/h. If I go an average of 32km/h I can get about 20km range. If I had 48v and a bit more ah I could pull off your trip doing about 30km/h average and be able to climb those hills but a lot depends on wind bike setup and a few other factors. My bike is about 110 pounds. The x5 is about 25 pounds the batteries weigh 30 pounds. I carry a toolkit with spare tubes co2 inflater with 2 refills tape screwdriver adjustable wrench 6 feet of 3/4 inch aircraft cable commercial padlock umbrella two chargers 3 garbage bags 1 ziplock bag and a few other odds and ends but if I go 60km it would not even go past 1hour of riding even with big hills. If I had those big hills to climb a lot I would help the motor out a bit and hopefully be able to coast down the other side which would give some regeneration benifits. If you run the x5 at 80v things change, It takes a bit more watts from the batteries to do the same speed but with the packs wired in series the amp hours drains much slower at moderate speed. If you mash the throttle it sucks up juice quickly and you draw 3000w or more at topspeed but torque is multiplied by about 4x and quick bursts of throttle get you rolling for long distances. The other setup that comes to mind for me would be a geared hub motor that would climb those hills well but would have a harder time at higher speeds. Their are chaindrive systems that seem to work well but I have no experience with them. I stayed away from those because removing pedals was not an option for me, more moving parts to break more drivetrain noise and changing a tire can be difficult with some.

 

[dogman dan]

Looking closely at the data of your ride, I see I was missing something. Being american, I can't stop thinking in stupid miles and feet. Your elevation gain is meters not feet. Your climb is very similar to the one I tried to do the other day, testing a ping pack at 101F. I got about 2/3 of the way up it, till I hit the 15% part on my cheapie brushed hub at 36 volts. It climbs well, but as I slowed, the power used started to overheat the controller and the motor, and the controller shut down several times. Getting up that climb at a fast speed will be very hard, but a good geared motor, hub, or using the chain gears, on 48 volts lithium would be the starting point to do it. You will still get up the hill a lot faster than you could peadle it. I could do that ride on my unelectrified bike if I wanted to, but I'm too lazy and won't.

 

[Mark_A_W]

Abraham, how much money are you willing to spend, weight to carry, and how far outside the law are you willing to go?

We just built a bike for my brother with a GL2 motor from Brett Solarbbq (it took 5 months to arrive..), a 48v 12ah LiFeP04 battery and torque arms from Getadirtbike (John).

It has a 20amp controller and charges to 54v (1080w in, maybe 650w out). Motor is about 6.5kg, battery is about 7kg I guess. The motor will handle 72v 30 amps or so I think - Knuckles is running that into the same motor.

It'll do ~45kmh with pedalling on the flat, should have about 50k range. Battery is in the triangle so it handles well (rear motor and rear battery is BAD).

Actually has less pickup than my bike, but keeps going after I have topped out at ~40kmh.

Cost about $1500 to add to a mountain bike.

I don't think you should be going much faster than 40-45kmh...it's just too dangerous. I slid out last week, going slow, but it gave me a fright (wet tyres on slick ashphalt).

 

[dogman dan]

I think he said he wanted to go 28 kph up the hill. at 13% he'll be doing about 90 kph down if he lets it roll. When i was coming down the big hill the other day I was able to controll my speed by putting just a hair of throttle on. The wheel then tried to regen, and slowed me to about 35 mph. Coasting, I would havd been doing about the speed limit of 65mph.

 

[Mark_A_W]

Might not be practical though....

Motorcycles to have their place, or maybe an e-motorcycle.

Or go a bit slower up the hill and stick to a lighter system. Or go through the gears (elation kit).

 

[JennyB]

I should do separate calcs for ascending, descending, and flat. My Garmin says I used 2350 calories on the ride, so the above is clearly not a perfect representation. If I could do that ride on an ebike using just 0.36kWh, damn but I think the ebike would use way more, to ascend and to overcome the extra bike weight.

It's not perfect because it doesn't account for the hills. The quick way to do that is to assume that you were using as much energy as you would have cycling on the flat at 29.5 kph for the same time. That's just over 200 watts for 2.2 hours - 0.44 kWh. Allow 60% efficiency and you need at least 0.73 kWh of battery. Two hundred watts is a good aerobic output for a fit-but-not-racing cyclist. I'm guessing you have a peak output of 450 watts and can sprint to 45 kph on the flat, or up a 13% grade at 13.2 kph.

Another way to look at it is that 1 watt hour of energy will lift 1 kg 300 metres, so the energy you expend going forward could raise you just over 680 metres in an hour, or 680/29.5 = 23 metres per kilometre. To climb a 2.3% grade at the same speed you need twice the power. Let's assume the same ratio holds for an ebike, which is a bit harder to pedal, and also a bit heavier. If the weight is significantly greater you will need to recalculate this ratio, the "cyclist's divisor" (see http://bushnell.homeip.net/~bill/bike/index_article)

So, the 62.5 km distance equates to 62.5*23 = 1437.5 metres vertical

Add the 6 metres of net altitude gain = 1443.5
The 739 metres gained lost count half = 369.5
443.5+369.5 = 1814 metres vertical, which equates to 1814/23 = 78.9 km on the flat, predicting a finish time of 78.9/29.5 hours, or just over 2 hours 40 minutes.

You'll need to spend about six times your overall weight to equal or better the time. If the weight is 100 kg you need at least 600 Wh (1kWh of battery at 60% efficiency), and a motor about 300 watts.

 

[voicecoils]

Abraham, how much money are you willing to spend, weight to carry, and how far outside the law are you willing to go?
I don't think you should be going much faster than 40-45kmh...it's just too dangerous. I slid out last week, going slow, but it gave me a fright (wet tyres on slick ashphalt).

Cool to hear about your brothers system. Sounds pretty good.

As for your questions I'm still trying to work this all out. Budget of ~AUD1.5k MAX excluding bike (which still means a few things need to go up on ebay )

I made the post as I was curious if there were good calc tools out there to help you design an ebike based on your needs, and also to see if my cycling abilities could easily be smashed by an ebike. It seems over my weekly Saturday ride flat speed would be no trouble but the hills and distance would mean a pretty beasty ebike would be required. Thats good to know!

I'm more interested in ebiking for commuting, transport, hauling, and the ev grin Carrying my backpack on the bike (on a rack), groceries, etc without breaking a sweat. I've found commuting to Uni frustrating as I arrive sweaty and breathless and have to at least change my shirt. That's after a 15-20min ride. Keeping with traffic is a good workout! If the uni had showers and lockers, that'd be great, but there's lots of "if"

I find 55kmh scary on my road bike if the downhill road gets bumpy, but I can't really visualise doing the same with a *much* heavier bike.

 

[voicecoils]

I'm guessing you have a peak output of 450 watts and can sprint to 45 kph on the flat, or up a 13% grade at 13.2 kph.

You'll need to spend about six times your overall weight to equal or better the time. If the weight is 100 kg you need at least 600 Wh (1kWh of battery at 60% efficiency), and a motor about 300 watts.

Interesting stuff! Lots to chew on. Thanks for the post JennyB.

I'm probably more appropriately not-fit-and-not-racing but I have my youthfulness to aid in spinning alongside wiry spandax clad middle age guys moving in packs and shouting about everything

I haven't ridden a bike with a PowerTap or similar so I don't know what I can output. On a very slight decline I can hit 53 kph in 53/12 gears. Uphill, I'm usually too out of it to keep my eyes on the speedo! But yours is probably a very reasonable estimate.

Cool, The 6x weight in Wh sounds like a clever calc if it works.

 

[Mark_A_W]

Abraham, how much money are you willing to spend, weight to carry, and how far outside the law are you willing to go?
I don't think you should be going much faster than 40-45kmh...it's just too dangerous. I slid out last week, going slow, but it gave me a fright (wet tyres on slick ashphalt).

Cool to hear about your brothers system. Sounds pretty good.

As for your questions I'm still trying to work this all out. Budget of ~AUD1.5k MAX (which still means a few things need to go up on ebay )

I made the post as I was curious if there were good calc tools out there to help you design an ebike based on your needs, and also to see if my cycling abilities could easily be smashed by an ebike. It seems over my weekly Saturday ride flat speed would be no trouble but the hills and distance would mean a pretty beasty ebike would be required. Thats good to know!

I'm more interested in ebiking for commuting, transport, hauling, and the ev grin Carrying my backpack on the bike (on a rack), groceries, etc without breaking a sweat. I've found commuting to Uni frustrating as I arrive sweaty and breathless and have to at least change my shirt. That's after a 15-20min ride. Keeping with traffic is a good workout! If the uni had showers and lockers, that'd be great, but there's lots of "if"

I find 55kmh scary on my road bike if the downhill road gets bumpy, but I can't really visualise doing the same with a *much* heavier bike.

My brother fitted a speedo yesterday.

With a GL2 motor, at 54v 20amps (48v battery fully charged), he "super cruises" at 47kmh on the flat with medium pedalling. (My bike tops out at 40kmh with fairly hard pedalling on the flat.)

He actually slows it down to 40, due to a desire to keep living.

Uni doesn't have showers and lockers? WTF? Surely there's sporting facilities? COMPLAIN ABOUT IT!!

 

[Timbo]

Abraham, how much money are you willing to spend, weight to carry, and how far outside the law are you willing to go?

We just built a bike for my brother with a GL2 motor from Brett Solarbbq (it took 5 months to arrive..), a 48v 12ah LiFeP04 battery and torque arms from Getadirtbike (John).

It has a 20amp controller and charges to 54v (1080w in, maybe 650w out). Motor is about 6.5kg, battery is about 7kg I guess. The motor will handle 72v 30 amps or so I think - Knuckles is running that into the same motor.

It'll do ~45kmh with pedalling on the flat, should have about 50k range. Battery is in the triangle so it handles well (rear motor and rear battery is BAD).

Actually has less pickup than my bike, but keeps going after I have topped out at ~40kmh.

Cost about $1500 to add to a mountain bike.

I don't think you should be going much faster than 40-45kmh...it's just too dangerous. I slid out last week, going slow, but it gave me a fright (wet tyres on slick ashphalt).

Mark, your brothers bike sounds awesome! Have you posted any pics around here somewhere?