Some costs

In my probably pointless pursuit of an electric powered replacement for my ancient Voyager, I've established some cost estimates for an electric powertrain roughly equivelent to BMW's C-Evo (long range version) - comfortably enough to produce Voyager-levels of performance, if not range. These are from local E-bicycle* enthusiasts and battery specialists.

There seem to be two routes to a custom battery pack, flat, rectangular "Apple-style" batteries that may be best for packaging but are known for exploding or catching fire if abused and smaller cylindrical, "Tesla-style/laptop" items, usually packed into 'cells', these are apparently more rocust and unlikely to combust. I'm currently focussing on these latter items. To replicate C-Evo output I'll need 2,500 of these packed into 150 cells that will wiegh 75Kgs, less than the Reliant/Guzzi powertrain. This number of batteries will cost, new, 5,400 Euro's (and probably £s by next year). I'll work up a package size optimised to fit in an FF keel area.

To this cost and wieght must be added a power management controller at £700, wieght unspecified but not huge. This is a programmable unit that can provide regen, traction control and torque limits and so on. Also a battery management system that seems to be regarded as simple and cheap. And a water-cooled motor, capable of 35Kw peak, 17 Kw continuous, at £2000.

So subject to some CAD work to establish battery packaging it's possible to buy a powertrain that will serve most prectical purposes for an FF. It'll cost about £8500, assuming a bit for the battery assembly and management, cabling, intumentation and so on (and £/Euro equivelence). The "Vehicle" end of an FF costs about £5,000 (ignoring the free labour of the enthusiast building it) which adds up to £13500, surprisingly similar to the cost of a C-Evo and an interesting insight into how much BMW must be paying for parts and labour. Not much of this can be found in scrapyards, although a frontalled C-Evo might supply a cheaper motor/rear end unit. (anyone?)

I'll publish a drawing, like previous ones, of the battery packaging in due course. This is not mysterious. The cells I've seen measure 102mm x 82mm x 70m. but need 10mm adding to the last figure to allow cooling airflow. Package 150 of these and you;ve cracked it. Meanwhile I'll have to get a ferry contract, or something, from Bozo to raise the dosh...

*In this world the term "bicycle" is used estremely flexibly, officer.

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Mental arithmatic

Instead of trying to do mental arithmatic while listening carefully to a battery specialist, himself trying to translate electronic speak into hammer action, I've gone home and used a pocket calculator. So you only need 125 cells to get 2,500 li-ion units, not 150. Doesn't make any difference to the price but highly relevent if you're trying to package the battery. Good job nobody takes any notice of this stuff...

Anybody listening?

Morning, Royce. Well, I'm paying attention. I have to admit, I didn't check your calculations. Just took them as read. I'd very much like to go the FF route, as we've recently bought an electric car, and I'm sold on the principle. However, range must still be an issue, if like me, you live in the country, and have miles and miles of tempting roads on your doorstep. My experience of our car is that you shouldn't charge it to 100% unless you're going to use it immediately, so 80% is the target for everyday. Also, the charge rate drops dramatically, once you reach 80% of battery capacity. So increased charging time also becomes a constraint. Then at the bottom end of the scale, you don't want to let the battery drop below around 10% charge, unless you're close to a KNOWN working charger. And that is forgetting that the 50Kw battery is restrained to only allow 45 or so usable units. So going back to our car, from a quoted range of 211 miles, you immediately lose 30% in day to day driving, although if planning a long journey, that would only go down to 10%, then in winter you lose another 10 - 15 % due to lower temperatures. So even if you manage to get a theoretical range of 150 miles from an eFF which would be class leading at the moment, you'd still only have a usable range of around 100 miles. More than enough for city riding / commuting, but not enough for touring / leisure. Of course battery technology appears to be progressing rapidly, so maybe in a couple of years, 150 miles of usable range will be available. At that point, I would be 100% converted.

Further work

Range is going to be the limitation for a while I think. The battery people here say that charging above 80% reduces battery life so you're on the money with your range remarks. Thay say the UK is good for EV's because it doesn't get hot enough to seriously need cooling, although some battery heating will help in mid-winter. I've done some work on the battery packaging issue, using the cells I mentioned. I'm supposed to get 125 in and so far I'm up to 102, inside the chassis I put up here recently. I'm going to do some more work on that but I doubt if I'll get to 125. 110 may be the limit and that will restrict passenger space. (2,200 individual units). I need to define motor dimensions and mess with the chassis a bit more. I'm thinking using a water cooled motor, then using the heat exchanger outlet air to heat the batteries on cold days (and me) but I can see a diesel heater being the answer there.

I guess that Aero's are the area where range can be extended, over a C-Evo etc. but that only works if you're going fast enough for it to matter. Tooling around Bristol in the 20 limit it could be brick (Bricks are of course quite good..) for aero purposes. The annoying thing is that it'll take three years to build, assuming I live that long, and the next-gen batteries will arrive around then, rendering most of this obsolete.

It's an interesting excercise though. I can understand why the E-Motorised bicycle people are focussing on recreational vehicles (Moto-cross, trials etc.) and lightweight urban scooters, it's really difficult to get enough batteries into anything longer range. The C-Evo is basically a battery box on wheels. The seat can't go any lower because of the batteries.

I think that, at the moment, instead of trying to replace something like a Voyager, it's down to acepting a limited range and designing a vehicle for a use where that isn't an issue - like Trials, commuting and so on. But with limited speed and range some FF advantages, aero efficiency, comfort, become less relevent.

eFF Analysis.

Royce, I'm sure you're correct about the type of eFF for the moment. Shorter range commuters, and lower speeds. But that experience will benefit the eventual eFF tourer, if I live that long. I'm currently wrestling with waterproofing the engine electrics on the Pete Lawrence Delta, after being left at the side of the road in torrential rain on Monday. No such problems on an eFF, I would imagine.

Cargo Scooter

The application that leaps off the page is an E-cargo scooter. Could be limited to 60 mph without loss of usability. It's also easier to package without a passenger option and would be easy to upgrade to E-Voayger spec. when better batteries arrive - due to neccessarily robust chassis and supsension details. I think I'll proceed, design-wise, on that basis.

Only snag is that it's clearly an industrial project not something Royce is going to use as retirement activity! Cue the whole sorry business of finding an industrial partner. One of the most significant things anyones said about my FF projects was "I think you're living in the wrong country" I'm not moving now, not that anyone would let me in. So I'm not going to build a prototype E-cargo scooter! But don't let that stop anyone else, younger, more naive and so on. (much richer would be a good starting point) but anyone can steal the design, but then the problem is that although they'll know what I've done, they won't know why. Could make development tricky. although for Honad it'll be 'almost simple', they'd just have to get over the corporate cowadice problem.

You should be relieved your 'water in the electrics problem' in only on the Delta, if it had been an E-FF you'd be keeping your head down in a ditch waiting for the molten battery parts to stop flying about...

Cell orientation

Make sure you stack the cells vertically. Horizontal stacking leads to more failures apparently, as the insides of the battery develop micro cracks due to bending loads.

Good tip

Thanks for that. It's very encouraging to see the accumalation of EV info. I'm relieved to note that the best packaging I've managed so far does align the individual battery units vertically.

I'd spend more time on this but right now I'm engaged in working out how to fit an earth return wire to the (Lucas)rearlight of a 1956 Norton 99 Dominator. The worst of it is that I know exactly what I did to deserve this...