Wisper battery life

[bogmonster]

Hi,

I don't own a Wisper and probably will not get one but I have looked at them and a quetion did arise.

The 905eeco has an 8ah battery that according the the docs does upto 15 miles unassisted and upto 25 miles assisted.

The 905se has a 14ah battery and does uptp 40 miles unassisted and upto 60 miles assisted.

So the eco has a battery that is significantly more than half the capacity yet goes significantly less than half the distance. Now I know that a larger capacity battery can withstand the same current drain more effieciently so therefore will outperform the smaller capacity battery in a non-linear fashion. Is that all there is to this or am I missing something else?

I have looked at the Alien 36v kit with a 10ah battery (think this uses the same motor but a different battery and speed controller) and does 20 to 25 miles according to the docs.

So, if that theory is correct, running a Wisper on 2 8ah batteries in parralel (this is a theoretical question by the way, I know there a real world logistical issues) would be much better than running it on one 8ah pack and then switchinbg to the other one the first one runs out. This setup would also be better that the 14ah battery? Is this correct or am I numpty?

I am considering thye Alien kit but the battery size is marginal for my needs. If I got 2 I am thinking I would significantly more than double the distance I could cover if I wired them in parallel?

Cheers, BM.

 

[wibble]

I dunno how to answer your question but I does lead me to another question.

Could two batteries make my bike more enthusiastic and faster at climbing steep hills?

Or is the poor hill climbing performance of ebikes a result of the motor and not the power supply?.

 

[flecc]

Two batteries in parallel give a very small increase in performance and a very small increase over the doubling in range. The very small gains really aren't worth the cost involved.

The real problem with hill climbing on hub motor bikes is that their motor is effectively in top gear all the time. A car stuck in top gear won't climb a very steep hill in exactly the same way.

The Panasonic motor drives through the gears so can handle just about any hill simply by selecting the gear to suit, just as one does in a car.
.

 

[Mussels]

I dunno how to answer your question but I does lead me to another question.

Could two batteries make my bike more enthusiastic and faster at climbing steep hills?

Or is the poor hill climbing performance of ebikes a result of the motor and not the power supply?.

It has more to do with gearing, if you want the motor to work well at higher speeds then it won't work so well at lower speeds. Unfortunately with a high geared motor and the bikes gears also on the high side for level ground performance then hills are a problem. I have got around this by fitting a smaller chainring which makes my gear range far more suitable for hills and the improvement is very good.
Gearing also depends on your cadence and most e-bikes seem to be set for low cadence which is not to everyones preference.

 

[bogmonster]

Two batteries in parallel give a very small increase in performance and a very small increase over the doubling in range. The very small gains really aren't worth the cost involved.

The real problem with hill climbing on hub motor bikes is that their motor is effectively in top gear all the time. A car stuck in top gear won't climb a very steep hill in exactly the same way.

The Panasonic motor drives through the gears so can handle just about any hill simply by selecting the gear to suit, just as one does in a car.
.

FLECC

I can undertsand the gearing bit. My understanding is that most hub motors produce the most torque at about 8mph and highest efficiency near thier top end, say 15mph. I can get my pushie up my steepest hills at 6mph so with some motor input reaching 8mph should be fine.

Still, I am not sure why the 14ah Wisper has a proportionaly longer range than the 8ah? On further reading I see that the battery chemistry is different so maybe this is it.

As for the Alient kit, it specifies 20 to 25 miles range whereas the Alien Cruiser with what I think is the same motor and battery gives 25 to 30 miles?

Not trying to cause an argument, just trying to get a better understanding.

Cheers, BM.

 

[flecc]

I don't know the Aliens BM, so can't really say anything on those. The Wisper differences are not solely due to the 8 versus 14 Ah capacities and chemistries, the motors on the two bikes are possibly different and differently internally geared. In total the differences are too great for comparisons of range and capacity only.

The Wisper 905se doesn't line up to the traditional view of 8mph for maximum torque and near 15 mph maximum efficiency I'm afraid. The reason is that's the motor is geared not for the legal 15 mph but for around 18/19 mph maximum with restriction applied to make it legal, the extra speed available via boost.

This makes it's maximum torque probably at or just over 10 mph, so it won't have much left at 6 mph. Likewise maximum efficiency will be at about 16 to 17 mph.
.

 

[bogmonster]

I don't know the Aliens BM, so can't really say anything on those. The Wisper differences are not solely due to the 8 versus 14 Ah capacities and chemistries, the motors on the two bikes are possibly different and differently internally geared. In total the differences are too great for comparisons of range and capacity only.

The Wisper 905se doesn't line up to the traditional view of 8mph for maximum torque and near 15 mph maximum efficiency I'm afraid. The reason is that's the motor is geared not for the legal 15 mph but for around 18/19 mph maximum with restriction applied to make it legal, the extra speed available via boost.

This makes it's maximum torque probably at or just over 10 mph, so it won't have much left at 6 mph. Likewise maximum efficiency will be at about 16 to 17 mph.
.

OK, maybe the 905se has a higher gearing, that would explain the extra range. On the 6mph topic, presumably if I can manage a sustained 6mph on the steep hills under my own steam, I am guessing that, providing I get to crank up the throttle early enough so as not to lose too much momentum, the Wisper should add about the same sustained input as I can manage and I should be able to maintain 10+ mph up the same hills and get maximum torque? I would hope that me and motor could manage more than the 6mph I can manage with leg power alone and get me to the sweet spot of the Wisper motor? I know that the through the gears systems have better climbing ability but hopped a hub would provide enough kick for my hills and fitness level.

I can usually keep my bike around 17 to 18 mph on the flat sustained, maybe 19+ if it is not too windy. In my hilly area I average about 15mph on a pushie if the amount of up and down are net zero. My route to work sees me averaging 17mph wheras home sees me averaging 13 mph (lots of steep hills).

I can manage 14 mph on short steep hills but not the long ones. Heart, lungs and legs cave in, not too fit The big hills come at the end of my route so I have already done 22 miles in the morning and 16 miles in the eveneing by the time I reach the long slogs. The idea of an ebike is really just to help with the final 6 miles and the killer hills. This is why I really wanted a Cytronex.

BM

 

[flecc]

This is true to some extent, adding the motor to your pedalling effort enabling a higher climb speed. However, the effect is nowhere near as great as might be thought for two reasons:

1) The e-bike is much heavier and requires more total wattage (rider & motor) to do a given climb.

2) Higher climb speeds require far higher wattages to do the given climb, double the speed means double the wattage required. Here's two examples I've copied from one of my charts on the Agattu to show how much extra power is needed with even a slight speed gain:

Gradient.........Climb Speed..........Total Power Needed

14%.................... 7.5 mph ..................490 watts


14%....................... 6 mph.................. 386 watts


20%..................... 5.5 mph .................492 watts


20%..................... 4.5 mph .................400 watts

.

 

[john]

The Wisper 905se doesn't line up to the traditional view of 8mph for maximum torque and near 15 mph maximum efficiency I'm afraid. The reason is that's the motor is geared not for the legal 15 mph but for around 18/19 mph maximum with restriction applied to make it legal, the extra speed available via boost.

This makes it's maximum torque probably at or just over 10 mph, so it won't have much left at 6 mph. Likewise maximum efficiency will be at about 16 to 17 mph.
.

Strictly speaking, maximum torque is at 0 mph for all motors. I think flecc is referring to maximum power at about 10 mph (a useful measure). You get help on hills all the way down to 0 mph but at low speeds (full throttle), most of the energy is used to make heat rather than pushing you up the hill.

 

[bogmonster]

Strictly speaking, maximum torque is at 0 mph for all motors. I think flecc is referring to maximum power at about 10 mph (a useful measure). You get help on hills all the way down to 0 mph but at low speeds (full throttle), most of the energy is used to make heat rather than pushing you up the hill.

Every cloud has a silver lining. At least if I'm going slow I can warm my hands up in the winter.

 

[flecc]

Strictly speaking, maximum torque is at 0 mph for all motors. I think flecc is referring to maximum power at about 10 mph (a useful measure). You get help on hills all the way down to 0 mph but at low speeds (full throttle), most of the energy is used to make heat rather than pushing you up the hill.

I am referring to torque John, at the speed where maximum torque and power coincides. About 70% of the speed band below that point and down to 0 mph is of little or no practical use to e-bikers, hence my ignoring the non-useful torque every time I post on this.

So no silver lining of going very slow and hand warming for BM on the 905se.
.

 

[john]

Here is a typical profile for an eZee motor:

 

[bogmonster]

I had just convinced myself to buy the Alien kit, just waiting for the next pay packet. Unfortunately Alien has switched back to 110mm width hubs instead of the 100mm they were using for a bit. My forks are at 100mm. They are aluminium, not steel, so bending then is not easy. I have given up on the ebike idea for now. Yes, I know I could get new forks but I really can't be bothered anymore.

Everything on the market is either too expensive or not practical for my application. The Alien kit wasn't perfect but the price was more realistic. Not sure that 110mm will fit many forks though. Oh well, better get fit....

 

[flecc]

Here is a typical profile for an eZee motor:

View attachment 447

It's a pretty picture, pity the reality is so different. Riding two of these in a hilly area, I know how useless they can be once speed falls well below the maximum torque/power point.

I'm trying to give practical advice of use to e-bikers, and theoretical graphs which assume a constant power supply aren't much help in that respect. Our batteries can be sadly wanting in actual hill climb conditions when up to 18% voltage drop is less than helpful.
.

 

[Wisper Bikes]

Hi,

The 905Eco has an 8ah battery that according the the docs does up to 15 miles unassisted and up to 25 miles assisted.

The 905se has a 14ah battery and does uptp 40 miles unassisted and Upton 60 miles assisted.

So the eco has a battery that is significantly more than half the capacity yet goes significantly less than half the distance. Now I know that a larger capacity battery can withstand the same current drain more efficiently so therefore will outperform the smaller capacity battery in a non-linear fashion. Is that all there is to this or am I missing something else?

Cheers, BM.

Hi Mr Monster

There is a very simple answer to you question. We have road tested the 14a battery for range but not the 8a. I didn't want to claim it would do more than it actually could so I made a very low estimate.

We will have performance figures on the eco before the end of the month.

Best regards David