How Best to Tackle Hills on a Longer Ride?

[stever1957]

I have yet to buy my first electric bike, but it won't be long now. I'm leaning towards the Woosh Big Bear, as I'm around twenty stones.

It seems to me that two main considerations are not to stress the motor excessively and not to expend too much of the battery's charge.

Now, given that I'm happy to do a fair bit of pedalling, I'm curious to know how best to approach:

A] Degree of pedal assist (1, 2, 3 etc).
B] Gear selection (lowest gear or not).

Any tips would be appreciated.

 

[Woosh]

pedal normally and top up your effort with the throttle.
You don't have to change gear or assist level, the throttle has priority and control how much current is needed.
The Big Bear is fitted with Bafang BPM motor, it's a very robust motor, not easy to stress.

 

[stever1957]

pedal normally and top up your effort with the throttle.
You don't have to change gear or assist level, the throttle has priority and control how much current is needed.
The Big Bear is fitted with Bafang BPM motor, it's a very robust motor, not easy to stress.

So, if I were approaching a hill, on the flat, in a high gear on, for example, assist level one, I should remain in that high gear up the hill?

 

[tommie]

So, if I were approaching a hill, on the flat, in a high gear on, for example, assist level one, I should remain in that high gear up the hill?

Nope!

you still think as you would on an ordinary push-bike.

steep hill approaching, be ready to get up to your 28 or 32 cog,

then your assist level will need to go up to 4 or 5 maybe (depends on how easy or difficult the hill)

you`ll soon get the idea, just don`t let the motor bog down, keep a highish cadence !!

 

[flecc]

So, if I were approaching a hill, on the flat, in a high gear on, for example, assist level one, I should remain in that high gear up the hill?

No, you'll need to charge down, and how much is determined by your pedalling. As you go into the hill the bike will slow and your pedal rotation rate (cadence) will slow. Keep it at normal levels like at least 60 rotations per minute by changing down so you can help the motor effectively. Use the throttle as needed to assist you with that.

N.B. Crossed with Tommie's post.
.

 

[stever1957]

Thank you both.

That is exactly as I would have imagined.

 

[Woosh]

Thank you both.

That is exactly as I would have imagined.

their comments are suitable for crank drive bikes where your motor will thank you for selecting the right gear. You are not driving your car up a steep hill in the fifth gear.
The Big Bear is a hub drive, the torque you get does not depend on the gear you are in.
So relax, you can control the climb easily with the throttle.
Generally speaking, the rider's output is best at their natural cadence. Bikes fitted with geared hubs are very good for long and tough hills because they don't force the riders to be out of their comfort zone. For the Big Bear, it can climb on throttle alone up to about 14% gradient.
So select the gear that you feel most comfortable at and let the motor earn its keep.

 

[DynatechFan]

what woosh said

I have a couple of long steep climbs on my commute and worried about the motor getting really hot running at full assistance for many minutes - so much so I used to stop and check, it never even seemed to be warm. Below 5mph the motor starts to get a bit noisy so I am guessing it is less efficient there but these geared hub motors are simply amazing

EDIT - to clarify - by steep I mean 15% to 18%, by long I mean about 300 to 500m. Un-assisted these are deeply unpleasant hills

 

[GLJoe]

The Big Bear is a hub drive, the torque you get does not depend on the gear you are in.
....
Generally speaking, the rider's output is best at their natural cadence. Bikes fitted with geared hubs are very good for long and tough hills because they don't force the riders to be out of their comfort zone.

I'm not going to disagree with what you said, however can I point out that the OP originally said: "...not to stress the motor excessively and not to expend too much of the battery's charge"
So taking those (very valid) questions at face value, if you're prepared to pedal and put some effort in (which the OP also said), then what's the best way to climb a hill - because climbing with too low a speed is going to waste electricity and in doing so, heat up the motor.
??

 

[Woosh]

So taking those (very valid) questions at face value, if you're prepared to pedal and put some effort in (which the OP also said), then what's the best way to climb a hill - because climbing with too low a speed is going to waste electricity and in doing so, heat up the motor.
??

On a geared hub like the BPM, its maximum output is about 650W.
let's assume for the sake of argument that the gradient is 8%, your weight is 90kgs, bike + stuff you carry = 30kgs and your comfort zone is 60 RPM, that is where you can pedal most efficiently and at that cadence, you can sustain an output of 150W.
Let's use the emulator at ebikes.ca

Parameters:

Total energy = 650W + 150W = 800W available to climb that 8% gradient.
Bike + rider = 120kgs
Gradient: 8%
Motor BPM, controller 20A battery 36V 15AH, 26" wheels, front = 44T, rear: 13T-32T, wheels: 26"

calculated speed: 21.5kph = 13.4mph

Your selected gear is 13T rear, gear: 7th.
No need to change gear.

 

[Nealh]

Trial and error Steve so what ever suits you.
Ride like a normal bike and select an assist level that feels good & comfortable.
I select a lower gear and higher assist for peddling as I also want the effort and exercise, as I build up speed or find my cadence is too spinney I go for higher gear.
It all boils down to the type of rider you are.

BPM is a bit of a monster hub wise you will find it hard to stress, my preference is lowest gear I can get away with.

 

[GLJoe]

On a geared hub like the BPM, its maximum output is about 650W.

Ok. What speed is its max efficiency of that particular motor though?

calculated speed: 21.5kph = 13.4mph
Your selected gear is 13T rear, gear: 7th.
No need to change gear.

13.4mph is a fairly quick though (for a hill), so would I be right in thinking that you are still in a pretty efficient speed zone?
If so, then that would imply you're not overheating the motor, and not wasting battery power as heat. Sounds good!
It does however seem to contradict the advice the other posters above gave though

 

[Woosh]

Ok. What speed is its max efficiency of that particular motor though?

that motor has winding code 13, maximum efficiency: 15mph, maximum speed: 20mph on 26". Maximum torque: 4mph.
You can also run it at 48V but my 48V SWX02 code 16 beats it on hills and is lighter.

 

[stever1957]

One thing's for certain: it's going to be fun finding all this stuff out for myself.

Thank you all.

 

[flecc]

It does however seem to contradict the advice the other posters above gave though

Not really. Woosh quoted for an 8% gradient which as far as I'm concerned is only just starting to be a hill. My advice and no doubt other's was for a range of hills.

No-one is going to be flying up 14% to 25% hills at around 15mph, Big Bear motor or not.
.

 

[anotherkiwi]

I you want to provide your 150 W you have to be at your best cadence and to be at cadence you have to be in the correct gear. If you don't have a throttle you will need to change down a gear or two.

The Mxus (rear hub) will climb 9% average gradient hills of 2 km long at 25 km/h if you are in the right gear - 48:22 in my case. A spot at 13% had me change down to 48:24.

And... if you are in the correct gear you will get better range from the battery! You get quite a few hills in 52 km...

 

[chris_n]

On a geared hub like the BPM, its maximum output is about 650W.
let's assume for the sake of argument that the gradient is 8%, your weight is 90kgs, bike + stuff you carry = 30kgs and your comfort zone is 60 RPM, that is where you can pedal most efficiently and at that cadence, you can sustain an output of 150W.
Let's use the emulator at ebikes.ca

Parameters:

Total energy = 650W + 150W = 800W available to climb that 8% gradient.
Bike + rider = 120kgs
Gradient: 8%
Motor BPM, controller 20A battery 36V 15AH, 26" wheels, front = 44T, rear: 13T-32T, wheels: 26"

calculated speed: 21.5kph = 13.4mph

Your selected gear is 13T rear, gear: 7th.
No need to change gear.

The OP is 20 stone so 217kg plus bike so maybe around 240kg. 8% is an incline not a hill

 

[Woosh]

The OP is 20 stone so 217kg plus bike so maybe around 240kg. 8% is an incline not a hill

The OP is on the Isle of Wight.
using the simulator at ebikes.ca,
20 stone = 127kgs
bike + rider = 150kg
Rider output: 150W
motor BPM, 20A controller, 26" wheels, 44T chain ring, 8% gradient:

calculated speed: 10.6 mph, 141 RPM.
if his optimal cadence is 60 RPM, then he needs 18T at the rear cog.

Best gear: 5th (18T, Shimano TZ21 freewheel 14/16/18/20/22/24/28)

 

[chris_n]

The OP is on the Isle of Wight.
using the simulator at ebikes.ca,
20 stone = 127kgs
bike + rider = 150kg
Rider output: 150W
motor BPM, 20A controller, 26" wheels, 44T chain ring, 8% gradient:

calculated speed: 10.6 mph, 141 RPM.
if his optimal cadence is 60 RPM, then he needs 18T at the rear cog.

Best gear: 5th (18T, Shimano TZ21 freewheel 14/16/18/20/22/24/28)

So now we have gone down two gears and we are starting to make significant heat, your 800W in is now probably less than 600 out and slowing down. This is getting you further away from your optimum rpm than your original scenario making more heat instead of propelling the bike.
At what point will it fail? Will it make my local 10% average hill over 10km with air temperatures in the twenties and me weighing 85kg? If it will do that one I can find plenty steeper