Hill climb

[eP]

safe

At the case when you climb at 3-4 mph on high slope road by 4-3 minutes it is on a big difference you lose another 20 secondns or all the minute.
It is 40 second difference.

So try to calculate how much energy it is possible to save when you go downhill at 3 times less speed and this slow speed is between 10-15 mph.

I'm sure it is a lot of energy which could held you increase your speed when you climb or climb unassisted.
So maybe this way you could ride even faster for longer distance.

 

[Lowell]

Better efficiency certainly doesn't hurt, but how far do you guys actually ride in one trip? I built my bike with my 21 mile commute to work in mind, which tt comfortably covers in 37 minutes while using 2/3 of the battery charge. Hub motors are no good on hills? 35mph up a 13% grade proves that wrong. Does anyone have a geared ebike that is faster up a similar grade?

 

[eP]

Better efficiency certainly doesn't hurt, but how far do you guys actually ride in one trip? I built my bike with my 21 mile commute to work in mind, which tt comfortably covers in 37 minutes while using 2/3 of the battery charge. Hub motors are no good on hills? 35mph up a 13% grade proves that wrong. Does anyone have a geared ebike that is faster up a similar grade?

Hi Lowell

If you climb at 35mph up a 13% grade, so what is your speed at opposite direction ?
At hilly area i can trip up to 30 miles, at flat much more - at really cheap old bike without any assistance.
So with assistance at critical paths ( high grade hills ) my range could grow up to 50 miles i hope (at small wh amount if i used regen at downhill).
Average 10 mph is good enough for me - i like to see all around when i cycling, especially at top of the hills. At higher speed i have to pay much attention to ground(road) to avoid bad surprice's.
I like cycling at sunny days(i'm not alone i'm sure) so it could be possible using small solar panels (40-60W) at stops at longer trips at such low average trip speed and high efficiency.
Big heavy cells and grid charger it is not good idea when you hilly cycling without acces to grid.
And for me (and many others) big battery price is still prohibitive.

 

[Lowell]

Better efficiency certainly doesn't hurt, but how far do you guys actually ride in one trip? I built my bike with my 21 mile commute to work in mind, which tt comfortably covers in 37 minutes while using 2/3 of the battery charge. Hub motors are no good on hills? 35mph up a 13% grade proves that wrong. Does anyone have a geared ebike that is faster up a similar grade?

Hi Lowell

If you climb at 35mph up a 13% grade, so what is your speed at opposite direction ?
At hilly area i can trip up to 30 miles, at flat much more - at really cheap old bike without any assistance.
So with assistance at critical paths ( high grade hills ) my range could grow up to 50 miles i hope (at small wh amount if i used regen at downhill).
Average 10 mph is good enough for me - i like to see all around when i cycling, especially at top of the hills. At higher speed i have to pay much attention to ground(road) to avoid bad surprice's.
I like cycling at sunny days(i'm not alone i'm sure) so it could be possible using small solar panels (40-60W) at stops at longer trips at such low average trip speed and high efficiency.
Big heavy cells and grid charger it is not good idea when you hilly cycling without acces to grid.
And for me (and many others) big battery price is still prohibitive.

Speed down an approximately 3% grade is 57mph. Down a 13% grade should easily be 60+mph but I've never tried.

As for weight, with a 180lb rider and a lightweight 55lb bike that's 235lbs total weight. My GVW is around 275lbs, only 17% more than the 'lightweight' bike, and it certainly makes more than enough power to move that extra 40lbs.

I don't consider $1000 on batteries to be cost prohibitive given that my bike can quite nicely replace a regular vehicle. At the current rate I'm racking up Km on my bike, after one year it will save me $1500-$2000 in gas alone at current prices. And that doesn't include tire wear, maintenance, insurance, parking etc.

 

[Matt Gruber]

ep
trip 30mi? u don't need a motor, u ARE a motor.
u need a candy bar.

 

[eP]

...Hub motors are no good on hills? 35mph up a 13% grade proves that wrong. Does anyone have a geared ebike that is faster up a similar grade?

Speed down an approximately 3% grade is 57mph. Down a 13% grade should easily be 60+mph but I've never tried.

I don't consider $1000 on batteries to be cost prohibitive...

I do understand You.
But keep in mind what i said before:
here

So i have 2 ideas for bike: 
1) economic with 2 motors: one geared for rear , and fast hub for front. 
2) powerfull with high power (and) high eff. hub for front.

So your vehicle is similar to my second idea.
The first one is for cheap vehicle for kids etc. whos dont care abot time and dont want spent huge money for it.
The same cheap vehicle could bring more plesure and comfort for older people which cycling for health.

So dont compare aples and oranges please.

For kids $300 is strongly prohibitive cost for batteries (especially in my country), so my first idea is for promotion e-bike style (to be trendy) for kids.
When this happend we all win as e-bike parts will be common, popular, cheap and good quality as buyers will know what they have to get for their money.

For yours style of driving regen will be impractical and cannot save important volume of energy for your energy hungry driving style.
But for cheap kids vehicle it is quite different story. I still wait for safe's analyze regen capability.
I would like ask you: try to drive at half the speed the same route and compare energy savings.

 

[scottclarke]

ep
trip 30mi? u don't need a motor, u ARE a motor.
u need a candy bar.

Quite right

I used to time trial back in the late 80's - but was aiming for bigger things so my daily commute was by cycle - 12 miles each way - followed in the evening by a trip to MK and back - 46 miles round trip.

I was so obsessed with keeping weight low - despite my (then) interest in electric drives - not once did I consider electrifying my bike. A good thing - since the batts around then gave me a 5 min flight tops!

If I was as fit now as then - I have to admit - I am not at all sure I would be interested in electric drive. For me it comes down to personal achievement - to be the best - a motor WOULD have been cheating. The whole point was to challenge myself.

With electric drive - it comes down to money - anyone with the £Â£Ã‚£$$$ can put a bike together and get top performance.

So, ep - I am surprised you seek electric drive if 30 miles is ok for you - you must be a new generation of human!

Hybrid?!?

Scott

 

[eP]

ep
trip 30mi? u don't need a motor, u ARE a motor.
u need a candy bar.

It is true
I have strong legs. They are much better than rest of my body so i relatively at short period of time could get god results from cycling.
But my heart dont like high grade hills, so i still fill how hard it work when i'm cycling at hills.

So for the sake of health i'm strongly interested in very good assistance.

 

[eP]

So, ep - I am surprised you seek electric drive if 30 miles is ok for you - you must be a new generation of human!

Hybrid?!?

Scott

I have in my memory how much i was proud when i ride 6 miles at once, a few month ago (when i started cycling regulary).
I'm quite ordinary human. Maybe even more lazy than others. I spent so much time on the net with my PC at home, so when i have to stay and wait by a while i see dark in my eyes and i have to sit down to recovery.
So since that time i've started regular exercises and regular cycling.
So starting hills cycling is hard and very good assistance you need at such hard terrain.

 

[safe]

As for weight, with a 180lb rider and a lightweight 55lb bike that's 235lbs total weight. My GVW is around 275lbs, only 17% more than the 'lightweight' bike, and it certainly makes more than enough power to move that extra 40lbs.

I don't consider $1000 on batteries to be cost prohibitive given that my bike can quite nicely replace a regular vehicle. At the current rate I'm racking up Km on my bike, after one year it will save me $1500-$2000 in gas alone at current prices. And that doesn't include tire wear, maintenance, insurance, parking etc.

Wow, only 55 lbs for a bike that pumps out 5000 Watts THAT'S EXTREME power for so little weight. It's tempting to simply build the "ideal machine" like that and allow price to not be a factor, but I would like to build something that doesn't cost so much. You can get $1000 worth of "energy" out of a NiMh battery pack for only about $600. It means that you add extra weight, but at 45 lbs you can get 1440 Watt Hours of "energy" which in not that bad.

Regen might make sense in very limited riding situations where you are constantly going up and down hills. People on flat land would get 0% performance from regen. People on hills might get as much as 30% back.

Factors to consider:

1. Wind resistance - You can't recapture that energy.

2. Battery charging - Charging tends to be about 50% efficient with most battery chemistries, so while you can capture the energy of the hill you will lose half of it due to charging losses.

3. Friction and Tires - All the other losses related to the tires and the friction losses from hubs, chains, and anything else cannot be recovered.

 

[Lowell]

My bike is about 100lbs. What I was saying is that the total weight is only 17% more than a 'lightweight' ebike, but with several times the power.

 

[safe]

My bike is about 100lbs. What I was saying is that the total weight is only 17% more than a 'lightweight' ebike, but with several times the power.

How many Watt Hours is the battery?

It's Lithium right?

I've calculated before that NiMh can give you 1440 Watt Hours for only 45 lbs. Add about 65 lbs for the bike and you get to about 100 lbs. So where is the weight coming from? (with Lithium cells you should be able to get down to under 75 lbs)

You must need a lot of battery in order to get decent range if you are consuming 5000 Watts. You don't need to consume all that energy all the time, but at low speeds your efficiency can't be very good. (that whole efficiency verses rpm thing) If I remember your bike setup you had a 5304 (or something like it) and a bunch of Lithium cells and a voltage near 90 Volts. That means that your efficiency is not very good below about 30 mph. (even though the torque is great) Once above 30 mph then the efficiency gets better and by 40 mph your bike would be "in the groove" and working really well.

 

[Lowell]

X503 hub in a 26" wheel, powered by 76 Nexcell 2D cells. The packs weigh a bit over 50lbs all together and give a nominal voltage of 91.2v. After using 3-4Ah, resting voltage settles around 97-98v.

A lot of my commuting is through 50km/h speed zones so I usually keep it about 10 over the limit except on the highway. I built the battery capacity around my commute, testing several different combos along the way. If there were more sections I could use full power on, I'd just add more capacity, and I'm keeping an eye on the average price of DC9360's on Ebay. I still want to build a 29sXp secondary pack of A123 cells to see what the X5 hub can really do.

From the other thread on X5 efficiency I managed 19.9Wh/km with a median speed just over 50km/h. Honestly it was the most boring thing I've done with the bike, ranking as only slightly more exciting than watching batteries discharge on an analyzer.

 

[eP]

From the other thread on X5 efficiency I managed 19.9Wh/km with a median speed just over 50km/h. Honestly it was the most boring thing I've done with the bike, ranking as only slightly more exciting than watching batteries discharge on an analyzer.

At the other thread you said:

Rode 28.4km this morning, max speed of only 65km/h, avg 35km/h. End result? 19.9 Wh/km.

So tell us what is the difference for your median and average speed

 

[Lowell]

From the other thread on X5 efficiency I managed 19.9Wh/km with a median speed just over 50km/h. Honestly it was the most boring thing I've done with the bike, ranking as only slightly more exciting than watching batteries discharge on an analyzer.

At the other thread you said:

Rode 28.4km this morning, max speed of only 65km/h, avg 35km/h. End result? 19.9 Wh/km.

So tell us what is the difference for your median and average speed

Mean average speed of 35km/h as read off the DrainBrain. Median speed is the speed cruised at for most of the ride. I would say close to 20km of distance was covered at 50-54km/h. Because of the non linear increase in power useage at higher speeds, it's sometimes more useful to look at median speed to get an accurate power consumption number. If I really open the throttle up a lot, Wh/km can go over 60. Combine that with a slow cruise along the beach, and you end up with some not very useful average data.

http://www.manatee.k12.fl.us/sites/elementary/palmasola/mathlabtutstat1.htm

 

[safe]

X503 hub in a 26" wheel, powered by 76 Nexcell 2D cells. The packs weigh a bit over 50lbs all together and give a nominal voltage of 91.2v.

I calculate that to being about 1824 Watt Hours which is (by most peoples standards) gigantic... that makes it a good match for the higher power output. I agree with the decision to go with NiMh since they are a lot cheaper to get into than Lithium. Your pack is roughly what I had in mind for my next couple of bikes... it seems "about right".

How much did you pay for those cells and where did you get them?

 

[Lowell]

X503 hub in a 26" wheel, powered by 76 Nexcell 2D cells. The packs weigh a bit over 50lbs all together and give a nominal voltage of 91.2v.

I calculate that to being about 1824 Watt Hours which is (by most peoples standards) gigantic... that makes it a good match for the higher power output. I agree with the decision to go with NiMh since they are a lot cheaper to get into than Lithium. Your pack is roughly what I had in mind for my next couple of bikes... it seems "about right".

How much did you pay for those cells and where did you get them?

Ebikes.ca supplied the packs, which I reconfigured to fit my frame better, and added 6 extra cells at the same time. I started with 2 x 24v and 1 x 36v packs. After the rework, I have 19, 28 and 29 cell packs, charged by a 24v and 2 x 36v chargers.

 

[eP]

Mean average speed of 35km/h as read off the DrainBrain. Median speed is the speed cruised at for most of the ride. I would say close to 20km of distance was covered at 50-54km/h. Because of the non linear increase in power useage at higher speeds, it's sometimes more useful to look at median speed to get an accurate power consumption number. If I really open the throttle up a lot, Wh/km can go over 60. Combine that with a slow cruise along the beach, and you end up with some not very useful average data.

Sorry it was my fault. The second one i've assume 20'' rims but i see you use 26'' rims.

Never mind my faults, but i see also you well know how badly go your wh/km when you open your throttle.
The one reason is air drag but the second one is heating loses at high current.

So tell us the way to get over 80% efficiency at high motor current ( over 50Amps ).
Try to calculate and we will see when you are wrong.
Because i'm sure it is impossible.

regards

 

[Lowell]

Mean average speed of 35km/h as read off the DrainBrain. Median speed is the speed cruised at for most of the ride. I would say close to 20km of distance was covered at 50-54km/h. Because of the non linear increase in power useage at higher speeds, it's sometimes more useful to look at median speed to get an accurate power consumption number. If I really open the throttle up a lot, Wh/km can go over 60. Combine that with a slow cruise along the beach, and you end up with some not very useful average data.

Sorry it was my fault. The second one i've assume 20'' rims but i see you use 26'' rims.

Never mind my faults, but i see also you well know how badly go your wh/km when you open your throttle.
The one reason is air drag but the second one is heating loses at high current.

So tell us the way to get over 80% efficiency at high motor current ( over 50Amps ).
Try to calculate and we will see when you are wrong.
Because i'm sure it is impossible.

regards

Heating losses? I wouldn't consider 85-90% efficiency to be bad for heat.

Take a 5304 in a 26" wheel, 100v at 60 amps, and cruise at 60mph with 90% efficiency. You seemed like a pretty smart guy until you said "it's impossible"

 

[eP]

Heating losses? I wouldn't consider 85-90% efficiency to be bad for heat.

Take a 5304 in a 26" wheel, 100v at 60 amps, and cruise at 60mph with 90% efficiency. You seemed like a pretty smart guy until you said "it's impossible"

At 60 Amps you get 60*60*0.4= 1440 W of heat.
60 mph =96 km/h = 800 rpm at 26'' rims. So you have 80 working volts and 24 volts for heating in that case and 77% efficiency (theoretical as we skip other minor loses, so the real eff. will be even sligtly less).

But im not sure if 4800 W is enough for air drag at 60 mph as you need 600 W at 30 mph, so at 60mph you will want 8 times more (2^3) = 4800 W for air drag only (+ 400 W for rolling resistance).
So 60A will not be enough in my opinion.
But maybe i'm not smart enough :? :?

So show yours assumptions and calculations (maybe i'm wrong but not this case i suppose).

For the efficiency you want you need much less motor
resistance (than actual 400 mohm ), 200 mohm for instance.
Regards

 

[Lowell]

4800W to the rear wheel is more than enough to go 60mph if you tuck in. As for the math, maybe Safe can give you some spreadsheet lessons and you two can debate theory and efficiency all day long.

 

[eP]

4800W to the rear wheel is more than enough to go 60mph if you tuck in. As for the math, maybe Safe can give you some spreadsheet lessons and you two can debate theory and efficiency all day long.

Maybe its enough (but i'm not sure at your's case as you need 20Wh/km at 30mph around. ), so even if its enough (or you can change your vehicle to be enough )
you have still efficiency far less from your 85-90%.
At 75% you get twice the heat as much as at 88% efficiency.
So you have two problems to solve: 1) how to put over 6kW to your motor
2) how to dispose excesive heat.

So i see two different ways to adress both.
1) rebuild your vehicle as much as you will need 40 Amps only for 60 mph speed.
2) use the same power motor but with half internal resistance.

I'm interesting in second way as it could great improve efficiency at low speed range especially for hills climbing.


But i see now you still belive you can get 85% or better efficiency at 60A.
So i must tell you again it is impossible at such high motor internal resistance = 400 mohm.

So dont send me to Safe but answer the simple question: what are going to do ?

 

[safe]

4800W to the rear wheel is more than enough to go 60mph if you tuck in. As for the math, maybe Safe can give you some spreadsheet lessons and you two can debate theory and efficiency all day long.

There's a difference between "peak efficiency" and the actual efficiency that you get at a particular rpm.

Efficiency is a "Bell Curve" that is biased towards high rpms.

...there are all sorts of things we could talk about as far as how the curve is shaped, the heat losses, the controller losses, torque, etc... but the "bottom line" is that I agree with eP that you don't actually get your "peak efficiency" all the time. If you operate with the idea that "peak efficiency" is the same (or even close) to your "average efficiency" then I'd have to say you would be wrong.

But with 4800 Watts at the rear wheel who cares? :lol:

(realisticially your "average" efficiency is probably about 70%, but it depends on how you ride)

 

[Lowell]

What I'm going to do is keep riding the same as I have been for 1300km, with no motor heating issues. Streamlining the bike is something on my list of things to do and it will happen as soon as I have shop time. As race season is in full swing, I've been quite busy with customer projects.

Peak input power to the motor as measured by the DrainBrain is 6600W. I'm actually planning to dyno the bike sometime, I'm just not sure if the DynoDynamics has sufficient resolution at such low power levels.

eP: If you like arguing, try signing up at ww.viperalley.com and post how your vtech honduh makes more HP per liter than their crappy truck motors. And gets better gas mileage...

 

[eP]

eP: If you like arguing, try signing up at ww.viperalley.com and post how your vtech honduh makes more HP per liter than their crappy truck motors. And gets better gas mileage...

I don't argue for arguing. I do it because i see you missing the facts.
And facts show us the heat power at 60Amps is 9 times more power at 20 Amps.

So efficiency is not matter of faith ( for example faith that X-lyte motor is so much excellent that any current can't burn it ) - it is the matter of facts.