New Battery 'Fair' Prices

[NRG]

I can compare directly my Proconnect to my hub powered Peugeot. Local terrain to me is hilly, over a 26~28mile ride the Peugeot will use about 12Wh / mile for an average speed of 15mph, raise the average to 17mph and it uses 14Wh or thereabouts.

On the runs I've made so far with the Proconnect over similar terrain they have averaged 15mph, the first was 8.2Wh and the second approx 7~7.5 Wh / mile. I can't be 100% sure the figures for the Proconnect are spot on as I'm taking the theoretical Wh of the battery and using the crude 5 segment battery display to work out the use. Even so given the possible error of the display the Proconnect is at worst about 7.5~8Wh.

I can get down to about 8~9Wh on the Peugeot with a lot more rider input, however, average speed drops to 12~13mph or less over the same terrain and distance.

Edit: Also I'm assuming as the Panasonic battery is new its at or close too 100% capacity. I can measure the Wh used directly on the Peugeot regardless of capacity.

 

[Trevor Holloway]

But the question was whether the batteries were fairly priced.

My kit conversion just needs a 36v power supply - when battery renewal time comes I can go out to the whole of the market and if I need a new rack to mount it then that becomes part of the cost.

It may be that in 18 months time there will be someone who is willing to re-cell existing cases (any volunteers ?).

 

[dan]

General rule of business: you charge whatever the market will stand. As has been said before, THIS market is too small and too specialized for any true 'bargains' to be available.

If anything will kill the e-bike market, it will be the replacement cost of a battery. Knowing you have a 'consumable' with a built in clock running from the moment you take delivery whether you use it or not, and may well be half the cost of the original bike, is a sobering thought. Even a Wisper - at the end of 2008 you could buy a 905se Sport for £1200, and if you did, a replacement battery now comes in at over £500 - if you actually need one yet!

Rog.

this whole thread sounds like an advert good old fashioned heavy cheap lead acid batteries

 

[NRG]

But the question was whether the batteries were fairly priced.

My kit conversion just needs a 36v power supply - when battery renewal time comes I can go out to the whole of the market and if I need a new rack to mount it then that becomes part of the cost.

It may be that in 18 months time there will be someone who is willing to re-cell existing cases (any volunteers ?).

Yes, but the question is too narrow IMHO. Taken at face value I'd say no they are not, however, the Panasonic batteries seem better value than most vs other commercial offerings due to the efficient way the Panasonic drive system uses them, hence the diversion....(they still represent a large uncomfortable outlay IMHO 2 years down the line.)

Also to add to my figures above, the Wh figures for the Proconnect were achieved in Eco mode with some use in Standard mode for steep hills. On the Peugeot to get to 8 or 9Wh I have to use my low speed setting all the time and to average 15mph+ I need to use the medium speed setting with some use in high speed as well...

 

[NRG]

this whole thread sounds like an advert good old fashioned heavy cheap lead acid batteries

Well maybe there's something to be said in favour of them, a friend of mine still uses an early Powabyke with SLA's, he's just replace them with some new ones with slightly larger Ah and the bike is running better than ever for local commuting...

 

[flecc]

this whole thread sounds like an advert good old fashioned heavy cheap lead acid batteries

Exactly why motor vehicles still use them a century later for their essential functions.

Nothing else is remotely reliable enough.
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[Mussels]

Yes, but the question is too narrow IMHO. Taken at face value I'd say no they are not, however, the Panasonic batteries seem better value than most vs other commercial offerings due to the efficient way the Panasonic drive system uses them, hence the diversion....(they still represent a large uncomfortable outlay IMHO 2 years down the line.)

That's like saying someone with a car that does 50mpg should be happy paying 40p a litre more for their petrol than someone whose car does 15mpg. The efficiency of the vehicle is irrelevent when discussing the cost of petrol.

 

[flecc]

The efficiency of the vehicle is irrelevent when discussing the cost of petrol.

But not irrelevant when discussing the value of the petrol.

It's the functional value of the battery that counts to the owner.
.

 

[Mussels]

But not irrelevant when discussing the value of the petrol.

It's the functional value of the battery that counts to the owner.
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In my example the value of the petrol is still greater for the driver of the 50mpg car, it doesn't explain paying an extra premium for the same fuel.

 

[flecc]

In my example the value of the petrol is still greater for the driver of the 50mpg car, it doesn't explain paying an extra premium for the same fuel.

Agreed, and showing that the car comparison was not valid in this case. I was observing the usage value to the owner of the two batteries under discussion. That wasn't just in miles covered but in demonstrated life to date.

Of course, only time will tell the final values since the current technology variations are too new to know with certainty the experiences of a large number of users. It was only after they had been discarded that we realised with regret the true value of NiMh e-bike batteries.
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[Wisper Bikes]

I really find it hard to believe that the Kalkhoff is so much more efficient than the Wisper. This must mean that Kalkhoff gets more external energy (human pedal power) than the Wisper. Or is energy being created somewhere? Do electric bikes not follow the laws of conservation of energy?

Or am I missing something still??

Hi Bruce, I have been in China for the last few days with one of the biggest suppliers of electric bikes to China and the rest of the world, they are also the China agent for Panasonic cells. I like you have had difficulty wrestling with this paradox so I asked the question. This my understanding of the position.

It is quite simple, and has nothing to do with the battery, nor much to do with the crank drive over hub drive system indeed they say the hub drive is actually about 15% MORE efficient than the crank drive. The big difference is between Torque and cadence sensors and the way they send current from the battery to the motor.

A cadence sensor when activated simply turns on the motor to the level the rider has set. So on high assistance the bike is doing a massive amount of work compared to the rider, the rider therefore uses less effort and the range is shorter. If however the rider was to choose a low setting the reverse would apply with the rider putting in more effort than the motor, thus increasing the range. The truth if course is a rider will nearly always choose the setting that makes riding the bike as easy as possible

A torque sensor turns on the power only during the time pressure is being applied to either pedal. This has the effect of giving less assistance to the rider than a cadence sensor would at high power. The advantage of torque over cadence is when climbing hills and a large amount of pressure is being applied to the pedal the controller can deliver a huge amount of power (30A and more) to the motor for a fraction of a second giving a lot of assistance but for such a short length of time that the motor does not burn out. This gives the impression that hill climbing is easier however during these times the battery is actually being depleted very quickly.

The most sophisticated systems now have torque and cadence sensors combined so a rider can chose which they prefer given the terrain they are covering and how fit they are feeling. We may be going down this rout ourselves in the not to distant future. The point is that we have been assured that we could increase our range by at least 25% simply by fitting a torque sensor. Where does the extra 25% come from? You guessed it, the rider!

So to answer your question, there are simply only two sources of energy on a pedelec, the battery and the rider. The energy they produce together drives the bike. If the rider puts in more energy than the battery the bike will seem to be more efficient. Of course it isn't.

To date this makes more sense to me than any other explanation.

All the best David

 

[brucehawsker]

Thank you all for the contributions. Especially, David, your last one. I will read all and reflect. Busy today!!!

 

[tillson]

To date this makes more sense to me than any other explanation.

I'm afraid it doesn't make more sense to me.

If I were to drive my car around stuck in one particular gear (which is effectively what a hub motored ebike is doing) , it wouldn't be very efficient over a range of different speeds and terrain. The various parameters may all align under certain conditions and make it temporarily efficient, but generally it wouldn't be operating in those efficient circumstances. This is why cars are fitted with gearboxes. Although not perfect, they allow the prime mover, electric motor or engine, to continue working closer to it's maximum efficiency as the external factors, speed and terrain, alter.

Therefore, the crank drive systems ARE more efficient. When the rider slows on a steep hill, they change to a lower ratio gear thus maintaining a similar cadence, and hence efficient motor speed, to what they were achieving on the level. Because the motor is totally independent of the gears on a hub motored bike, it can't take advantage of this. These types of motors slow and fall into an inefficient part of the performance curve and hence consume more energy from the battery per mile.

 

[flecc]

Two points David.

What matters to the rider is the capability as I've pointed out before. I can cover more distance on the Panasonic system than I can achieve with a hub motor system for a given amount of battery capacity. The more hilly the territory, the greater that differential can be. Secondly, I can climb a much steeper gradient with the Panasonic system than with the hub motor.

There is no argument that a large part of the difference is due to the effort I am able to use with the Panasonic system. However, a fair part is due to driving through the gears and that is an efficiency gain which enables that superior gradient ability. On the downside though, some of the gains are at the cost of slower speeds.

So ultimately the one system enables my limited contribution to be used to better effect to enable things the other system doesn't permit me. That's what matters to me and many others, since something that cannot match my need clearly won't suffice. That ability gain is mainly due to the drive through the gears.

The above is for e-bikes in standard trim, but there is an interesting aside to this.

By changing the gearing upwards, the Panasonic unit bike can mimic the hub motor one. It gains the greater speeds in favourable circumstances, it loses some of it's hill climb abilities and it's upper range capability reduces. The degree of these changes is directly related to the amount of gearing increase.

With nearly the maximum change possible with a Shimano Alfine hub gear bike, using a 17 tooth sprocket, assistance remains high and the bike assists to similar top speeds to your derestricted hub motor bike. The amount of that assistance power is lower, though still sufficient. However, the cost of that near maximum change is that the range drops dramatically, giving a roughly pro rata distance per Wh between the two. In rough terms from member's experiences, the Panasonic bike with half the Watt/hours (260) will cover about 20 miles, yours with about double (518) covers about 40 miles, using the full performance on both with yours derestricted to get speed ability roughly matching.

So when imitation is used to give direct comparison, there's nothing in it to speak of. The difference is reduced to the remaining drive-through-gear ability for the steepest hills.

Panasonic have in the past largely chosen to gear and program their systems for maximum efficiency at some cost to performance. That has changed a little very recently for these export markets though.
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[Trevor Holloway]

At some time in the future there will be electric bikes (both hub and through gear drive systems) on the second hand market with worn out batteries at knock down prices, where the owners can not justify original manufacturers battery prices.
At that point it should be possible to swap battery types / capacity - with a bit of bodging - which I think was the original basis of the question.

With 5 mins research I can get 3 x 12v 7.2Ah SLA for £20 each.

I must admit I would have to think twice (or more) as to whether the weight saving would be worth it.

 

[NRG]

David, I'd go back and ask again because, well with respect, the answer you have posted is just.... Chinese.

 

[jbond]

they say the hub drive is actually about 15% MORE efficient than the crank drive.

Could somebody just clarify. As I understand it, the Panasonic system is
- Motor
- Epicyclic gearbox
- Freewheel motor drive sprocket
- Chain
- Derailleur or hub gears
Is that right? Is the freewheel in the motor drive sprocket or in the motor gearbox? Some people have commented that the Panasonic system freewheels easier than a geared hub motor. Presumably the difference is the bearing and gear drag in a hub motor. These are both minimal but detectable when doing a spin down test.

Regarding the quote above, both systems have a gearbox so the only real difference in drive chain efficiency from motor to road is in the chain and derailleur or hub gear. A chain and derailleur is pretty damn efficient so I wonder what that 15% refers to. 99.00% compared with 99.15% perhaps. In other words, virtually nothing.

So we're left with two big differences.
1) The 2:1 range or so in the rear hub gearing means the Panasonic motor can be run at closer to it's optimum rpm and/or a high speed motor can be geared to allow more low speed torque. So a good hill-climbing gearing for the electric motor can still get top speed. Like having a geared hub motor that had internal gears of 5:1 for speed user-switchable to 10:1 for hillclimbing.
2) Controller strategy. Torque sensing encourages the user to pedal. And encourages no assist when it's not needed.

So then I wonder:-
- Can we duplicate this strategy or at least approximate it with a hub motor? Preferably external to a conventional controller. Perhaps using the current limit feature of the recent CAs.
- Are there any alternatives for DIYers to build a mid-mounted chain driven motor?

 

[flecc]

I really find it hard to believe that the Kalkhoff is so much more efficient than the Wisper. This must mean that Kalkhoff gets more external energy (human pedal power) than the Wisper.

So to answer your question, there are simply only two sources of energy on a pedelec, the battery and the rider. The energy they produce together drives the bike. If the rider puts in more energy than the battery the bike will seem to be more efficient. Of course it isn't.

In a further answer to both brucehawkser and David, the latter is making the point here that the electric assist bike is a hybrid system, and indeed it is.

However, you are both making the point that the extra power is from the human and that this makes it in some way not efficiency. That argument is fundamentally flawed, since if it's a hybrid system, the human input is a valid component which counts towards efficiency.

As observed in my previous post, the one makes better use of the human potential than the other for any given rider in terms of range and climb ability. That is due to efficiency.

The technical arguments about motors and systems can be a red herring at times.
.
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[NRG]

Could somebody just clarify. As I understand it, the Panasonic system is
- Motor
- Epicyclic gearbox
- Freewheel motor drive sprocket
- Chain
- Derailleur or hub gears
Is that right? Is the freewheel in the motor drive sprocket or in the motor gearbox?

Read Flecc's excellent web site on this...on the MKII version....I can testify to the really low drag /great freewheel this system has...

newpanunit

 

[jbond]

newpanunit

Thanks. So with a stationary chain, power off, no pedalling, freewheel is the same as with a conventional bike. eg rear sprocket freewheel and hub bearings. This compares with a hub motor where you've got heavier duty hub bearings, seals, and the internal freewheel along with planetary gears.

Pedalling without power, you have motor output shaft bearings and internal freewheel against the hub motors planetary gears and internal freewheel.

Pedalling with power, there are chain losses between motor and road, but otherwise about the same number of gears and seals. Running the chain round a very small (9t) sprocket is relatively inefficient. So overall I'd expect the hub motor to be marginally more efficient.

Purely on mechanical losses there doesn't look to be much in it. Slightly better freewheel unpowered on the Panasonic. Slightly better human powered through the pedals only on the Panasonic. Slightly better efficiency on the hub motor.

I'm reminded of this as a DIY approach
Endless-sphere.com • View topic - Low Weight, Low Power E – ASSIST
The Recumbent Bicycle and Human Powered Vehicle Information Center
Perhaps combined with a Cyclone freewheel front chainset