What makes an efficient on road e-bike?

[JohnInStockie]

it would be advisable to mount them in proper D cell holders though.

A D cell holder, whats that?

 

[flecc]

That weight either side of the carrier is ok John, but batteries perched on top of a carrier are not advisable. Apart from anything else, they restrict the bike's usefulness for other casual carrying.

I frequently bring a bike into a hallway carrying between five and seven kilos in shopping in panniers quite low down, and even with that tail weight, if I tilt the bike sideways a bit in my endeavours to hold the door open at the same time, the bike can tilt further and lift the front wheel sideways, getting out of control very easily. Those same forces on the road with several kilos on top of the carrier can cause problems, and in any event will make a bike less pleasant to ride. That's not conducive to making an efficient bike.
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[flecc]

In anser to your query, a D cell is the standard cell used in our NiMh packs, and a holder is a dummy D cell that can have a smaller cell inserted into it.

See here

 

[coops]

You've seen the extreme lengths I've had to go to in order to create two truly efficient bikes, one all purpose and one dedicated for performance, but in both cases I started with standard bikes, because for me the kit approach is not acceptable. Ordinary bikes are just not made for the job and have too many compromises with battery mountings and the like.

I was in at least 3 minds as to where to post this idea because of many current related threads, but i'm cross-linking it here because it seems very relevant to this one. See what you think: if its sound in principle & practice then it may achieve several things - to give an optional mod for those who may want or need it, to add interest to the 2nd hand Torq market, and to hopefully increase the market & awareness for the need for suitably geared motors for 26-28" wheels . If its unsound or inadvisable, then its back to the drawing board....

Oh, it may also give rise to an increase in home-build projects with nice little torquey motors & 36V (+1or2 more added cells?! ) battery builds .

Feedback please, what do you all think? (See what you've started flecc?! )

Stuart.

 

[Ian]

A D cell holder, whats that?

Perhaps I should have said battery holder, like this. It saves risking damage by soldering directly to the cells. It would be advisable to beef up the interconnections though with heavier copper wire.

 

[JohnInStockie]

@ Coops

I think we are still on a similar vein Coops. Although that Puma motor, although excellent, (this question might be stupid..) but wouldnt it be over the the 250W rule by basic design?

John

 

[JohnInStockie]

@ Ian and Flecc

What I was thinking was to have 20 x 11Ah tagged cells in series attached to a piece of ply, by cable ties or something in 2 rows of 10, 1 above the other with the wiring for power and for charging coming out of the waterproof bag which would be repeated on the other side of the bike. With straps they would tegether make a pannier that could be secured to the bottom of the side of the rack with velcro.

The power and charging cables would link in parrallel for connecting to the bike or the charger.

Possible or am I just showing my ignorance of the subject?

Thanks all

John

 

[flecc]

I was thinking the same Stuart, the threads do seem to overlap.

Ian, I wondered what John wanted with the D cell holders!
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[flecc]

That parallel arrangement is ok for usage, but not for charging John, packs should never be charged in parallel. You'd need to either charge one after the other or have two chargers.

Do you really need that sort of capacity though, it's a lot of weight to lug around?
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[JohnInStockie]

Flecc

Just thinking hypothetically at the mo. Each of those D cells weighs 166gms, so 20 would be 3.3Kg, 30 is 4.9Kg, 40 would be 6.6Kg, and 60 is a wopping 9.8Kg!!! (for ref, I carry the charger everywhere with me on my Twist, and I dont want to do that).

If I had a 36V motor like the puma (if theres a 250W version or one that can be adapted to 250W), then I would need at least 30 cells in series (or 60 in parrallel) and I would get power and range (esp from the 60).

 

[Ian]

John, your rows of 10 cells would be over 2' long and would be difficult to accommodate as panniers, 4 rows of 5 would be more practical. If connecting the two banks of cells in parallel it may be advisable to use blocking diodes in series with each bank to prevent cross currents flowing between them, Schottky barrier diodes are best as they have a low forward voltage drop.
As Flecc has said, charging the two banks in parallel is not a good idea as there is no way to ensure each bank is getting it's correct share of the current.

 

[flecc]

I thought perhaps that John meant side by side cell mounting, wiring top to bottom between each, as that would shorten the row to almost one half. That means link wires on tagged cells or rapid soldering onto normal cells of course.

If that's what you were thinking John, direct soldering onto the cells has to be done very quickly to avoid damage and I wouldn't normally recommend it even though I do it myself.
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[JohnInStockie]

Ian

I think I was thinking of connecting them the other way, which would make each bank of 5 roughly 6 inches wide? I suppose that ther are numerous ways of connecting them, but I think that the less wire the better..

EDIT Flecc beat me to it Yes that is what I was originally thinking, but I can see Ians point. Also I was only thinking of getting tagged cells.

John

 

[flecc]

That's fine John, but I don't know of tagged cells at that very good price of £8.50 for two. Those I've seen are usually about £10 each cell for 10 Ah, so would be very expensive. Battery holders like the ones Ian showed would be good normally, but the quality of those stocked by Maplin isn't good enough for high currents since the wire contacts are poorly made.
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[coops]

Although that Puma motor, although excellent, (this question might be stupid..) but wouldnt it be over the the 250W rule by basic design?

A very sensible & law-abiding question John

The short answer, I think, is no, not illegal by basic design, but possibly illegal depending on implementation :

I hadn't thought much to be honest, since the 200W UK/250W EU "rule" is very hard to interpret and almost impossible to either calculate or enforce: an "average" 250W could be quite easily managed I think, and should (in theory) give a good torque for hills so long as the top speed is kept to the 15mph legal limit and the current limit can be set to say 13-15A @ 36V (that bit I'm not sure how to do - needs correct controller electronics) need to limit the peak power output to around 5-600W and bring the "average" in line with ~250W (with occasional pedalling/freewheeling downhill should do it) - that would be no more power or speed than other bikes such as the Sprint, and I think certainly within the spirit of the law, and if it could be calculated, most likely to the letter too. The image I've seen show its "stamped" as a "250W" (rated/continuous power) motor too.

Obviously you could run at higher voltage &/or current, which would give higher speed &/or torque, but would also be over the legal limit for speed and/or probably "average power" too! Maybe we could fit our own limiter, for off-road?

Stuart.

 

[JohnInStockie]

So as I understand it, a bank of 5 x 4 batteries ( as each battery is 33mm x 59mm) would be roughly 8" x 6" at a depth of 1 cell, and wieghs 3.3Kg. With wiring and connectors and shielding (and maybe diodes) should come in at 3.5Kg max.

PS - I just found some cheap A4 plastic box files from Tescos (3 for a pound) that would be quite sturdy, and easy to manipulate....

 

[flecc]

Sounds fine John, but allow a touch more on length for cell bindings to hold everything still, say half inch on a row in total. It's best not to have them rattling around.
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[JohnInStockie]

Flecc - is its really as easy as that? The magic is beginning to look like science

 

[JohnInStockie]

Coops - This project of yours is contagious...

 

[flecc]

Feedback please, what do you all think? (See what you've started flecc?! )

Stuart.

Yes, I thought the same, I really do seem to have kicked off a movement. Wouldn't it be good if an enterprising frame maker put on the market a frame with rear of seat tube space for a battery and a choice of forks, standard or wide in both rigid and sprung formats.

That would be the answer to constructors dreams, buck up sales of kit motors and maybe goad the e-bike suppliers into listening to customers more.
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