How Much Battery . . . ?

[Torslanda]

 . . . do I need to make a pedelec with a range of 100-120 miles?

I've had a scan around the forum and thought we had a dedicated section/threads passim for leccy assist. Couldn't find one so putting the question out there.

Fairly soon I will be launching into e-bikes (can't say too much at the moment but essentially there will be factory bikes available and a range of conversions) building a demonstrator and having a play with something special to me.

Anyone who knows me will have already had their ears bent about my pet project but, until it materialises, it's staying firmly under wraps. Barf bags will be issued before the official unveiling.

The gist is as follows. I've always wanted a Velomobile but there are two big strikes for me. Firstly there is cost. I simply haven't got the money to stump up for one. Secondly, despite having the shop and a decent size shed, is storage.

Another consideration is fitness. I've lost every shred of condition I ever had over the last four years. Working 6 days a week with only Sundays to recover and, inevitably, there is always other stuff to deal with. Cycling has become almost a distant memory, so a leccy bike is the logical solution. Being certifiable something of a lateral thinker it occurred to me that a project that's been at the back of my mind for a long time could now become a possibility. I want an e-bike with some real range.

The latest models appear to use 36v 9Ah battery packs to achieve a (claimed) range of 30-35 miles. So how realistic is this? If I wanted to be able to do some serious distance do I just need 4 times the battery capacity and the range will quadruple? If not can someone explain to me how it all actually works?

Why do I want such a machine? I want to be able to make Long Itch without using a drop of diesel. In one hit. With everything in a trailer*. And because I can.

Feel free to offer advice, definitive answers or just take the piss . . .



*No, Polar Bear, I still don't think of it as 'camping'!

[Kim]

Barakta's trike (ICE Sprint, Falco HX250 hub motor^[1], 48V LiFePO4 battery) seems to achieve something like 7-7.5Wh/km on average for standard 1000m/100km rolling hills.  That's with a modest but steady contribution from the rider - she's okay on the flat but needs the extra power for any sort of climb.  Her battery is 820Wh, weighs about 12.5kg (in a quick-release racktop box that absolutely wrecks the handling) and should be good for 100km (we've never actually run it flat).  Double that and you're there, the only issue is where to put all that battery.  Use LiPo and you could save a fair bit of weight.

Yes, all else being equal range should scale pretty much linearly with battery capacity.  Motor performance is affected by voltage though (assuming it can run on more than one voltage), so comparing a 36V battery to a 48V battery isn't easy.

If you're going for uber-range, then multiple battery packs make sense - weight distribution is an issue.  Having to manually swap between them might even be desirable (don't have to carry all the battery on shorter trips, and if you've got to switch battery half way you won't go too far and get stranded).


I think manufacturer's range claims are relatively conservative, in that they expect e-bikes to be ridden by people who aren't putting out much in the way of useful power.  That's assuming EU-legal 250W/25kph pedlec type things.  All bets are off with the unrestricted high-power stuff, where assumptions will vary.  But if you're going for range you want to stay within the legal limits anyway - they make good engineering sense for maximising energy efficiency.


_{[1] Not a recommendation as such.  It does what it says on the tin, but I think there are now nicer solutions from other manufacturers, particularly if you're not confined to rear hub motors.}

[tom_e]

My sister did a trip across France like this.  Using a trailer with (I think) three batteries in total, doing about 150km per day.  She planned the accommodation ahead to make sure she had charging.  She made it, and had a good trip.  But I'm fairly sure she reckoned it wasn't worth the hassle in the end to try and carry that many batteries.  You have to stay on top of your charging routine at each stop and the extra weight means you use more battery to cover the extra distance.  This scales badly as you add more batteries, but the range is obviously also affected by the all-up weight - bike, your camping kit, you.  My sister is fairly light, though the bike wasn't (in common with many electric bikes).

She did like the electric bike for getting out without too much effort.  Reckoned you can trundle along at moderate speed just turning the pedals and enjoying the ride, or get some exercise and travel a bit faster.  It very much gives you the choice.

[Wobbly John]

Just an idea as you've brought up the leccy bikes and distance problem - sorry if it ends up hijacking the tread.

What's the situation with electric car charging points? Could electric velos be made so that they could use them? What are the problems?

[LittleWheelsandBig]

While TGVing down to Bordeaux at the beginning of June, my bike was parked next to a Belgian's rather nice ebike. Apparently it was a Swiss machine with a 40km/hr top speed and he was looking at doing 150km/ day between wineries, with loaded panniers. I didn't ask about how many batteries he was carrying or his recharging plan.

[Pancho]

I've been a big fan of e-bikes ever since I bought one circa 2001 so that Mrs P could lug a trailer with two sprogs + groceries up our local Hill.

I have 20 years to do it but come our car-free retirement, we'll have electric semi-recumbent trikes. Not the insanely expensive Kettweisel but something I've knocked together in my shed. I may start with the frame of one of the cheapo monstrosities that are available.

[Pancho]

Just an idea as you've brought up the leccy bikes and distance problem - sorry if it ends up hijacking the tread.

What's the situation with electric car charging points? Could electric velos be made so that they could use them? What are the problems?

I've seen it discussed on the endless sphere forum (the main, I think, diy e-bike watering hole) but, iirc, it's a non-starter. You'd need some electronic jiggery pokery to do all the data stuff to make the electricity flow. That said, there are some EV charge points that are just 3-pin sockets which would work.

[Kim]

Just an idea as you've brought up the leccy bikes and distance problem - sorry if it ends up hijacking the tread.

What's the situation with electric car charging points? Could electric velos be made so that they could use them? What are the problems?

Most electric car chargers are something other than a standard mains socket, for the simple reason that a car needs about 20 times more energy per mile, and it would take all night to achieve that at 13A.

Some of them do output 240V single phase, and could conceivably be used to power an e-bike charger, but you'd need a bulky connector and possibly some electronics to negotiate with the charging point as if it were a car.  And an appropriate smartcard/app to pay for the use.

Similarly, using hook-ups at campsites means you need a Ceeform plug, a decent length of cable and ideally an RCD.  That's fairly bulky too.


The other issue is that the majority of car-charging infrastructure is in places that you don't really want to take/leave your bike:  Motorway services, car parks, city centre parking bays with nothing to secure the bike to.


On the other had, unlike a car, you can usually remove the battery from an e-bike and bring it indoors for charging from a normal mains socket, and can fill the battery in a couple of hours.  No shortage of those, assuming you can negotiate for their use.

[Auntie Helen]

My 12aH bottle battery is good for at least 130km with assistance level at a half.

More info here: http://www.auntiehelen.co.uk/alfie-gets-an-electric-motor/

[JennyB]

On the other had, unlike a car, you can usually remove the battery from an e-bike and bring it indoors for charging from a normal mains socket, and can fill the battery in a couple of hours.  No shortage of those, assuming you can negotiate for their use.

This. I've never been refused a charge at a cafe stop (I only ask where I'm  planning to eat) and a decent charger will restore most of the energy you've used that morning in an hour or so.

Legal pedelec is the way to go: as a general rule of thumb, each extra 5mph of average speed will reduce the range you can expect by 50%. Hub drive is slightly more effect enter in flattish country, but through-the-gears is better for for hills.  Travelling light, I have used as little as 2 watt hours per km and been glad of it when I needed it. Six watt hours is more usual. As a general rule,  you can go 30% further than you would for the effort unassisted, even over Audax distances.
I managed 360k  (l took a few wrong turns) on the first day of the Mille Failte with a 720 wh battery and two one-hour
charging stops. I was charging at  480 watts, using two chargers in parallel, and, knowing how much I had used, timing them to stop before the final tapering off part of the charge cycle.

Normally you  should  not abuse your battery like that. For longest life it is best, like an electric car, to stay within the middle 80% of its capacity. Use a battery big enough that it will take at least an hour to drain, and if you have two use them parallel unless you have a good scenario for using one while the other charges.

[Torslanda]

Another numpty question. I've seen the insides of Tesla batteries and they seem to be composed of shitloads of AA type cells joined in series. Does this mean I can get stacks of LiFePO4s and make my own?

Not trying to oversimplify things but as the vehicle I'm wanting/doodling/planning is going to be a one off it makes sense to custom build the battery to fit the available space rather than shoehorn in something that's non-specific.

[Cudzoziemiec]

So you're basically promising us to rock up at Long Itch (or somewhere... ) in a shed-fettled electric velomobile with trailer? TEH FRICKIN AWESOME!!!1!1!!

[Joe.B]

Mrs B has Hainzmann systems, on one her ICE trike the other on her DF.  Both are legal 250W rear wheels motors a 2 and we have 2 1425Ah batteries.
Range is such a difficult and subjective thing the quantify as no single set of circumstances will ever be repeated but I can say with confidence that on rides of up to round 40 miles she has never run out of power.
Though she has 2 batteries we never go out with both. If a ride is expected to be particularly long and hilly, or if she feels that she may more dependent on the motor and spend more time in high power than normal then we’ll take a charger and ask to plug it in at the lunch stop.  I can only think of one occasion in the last couple years however that we have actually felt the need for that mid-day charge.

Yes, in so much as I’ve seen many batteries are just made up of single AA cells so making your own should be no problem.  I’d use tagged cells rather than the conventional button type, you’ll also need some battery management circuity which is easily obtainable.  I changed one a few years ago and don’t recall it being particularly pricy. Photo below.



P1020813 by Joe.Audax, on Flickr

[Torslanda]

Vielen Dank, meine Damen und Herren*












*"Cheers" <Bill Bailey>

[Torslanda]

So you're basically promising us to rock up at Long Itch (or somewhere... ) in a shed-fettled electric velomobile with trailer? TEH FRICKIN AWESOME!!!1!1!!

That's the general idea. No idea of the timescale but I'm working on it.

[Polar Bear]

Another numpty question. I've seen the insides of Tesla batteries and they seem to be composed of shitloads of AA type cells joined in series. Does this mean I can get stacks of LiFePO4s and make my own?

I think that the cells are 18650 cells and not AA.   There are plenty of vids on youtube of folk making their own battery packs form tearing down old laptop batteries and recovering the good cells.

[Torslanda]

You're spot on, Mike. 

I think it's going to need a bulk delivery from China for what I want thobut.

[Polar Bear]

I have a retired cycling friend who has more than a passing interest in electronics.   I will subtlely raise the prospect of knocking up custom battery packs for the purpose of providing extended running for like-minded assisted cyclists.

[Kim]

Thing about building 18650 battery packs is the boring physical practicalities.  You can't easily solder to the cells, which means you risk damaging them with too much heat.  The proper way to do it is spot-welding, but who's equipped for that?  Some sort of battery box, but that adds bulk, complexity and cost.

Find an existing battery from a supplier of batteries and use that.  Or get them built to spec.

http://www.pingbattery.com/ is good for LiFePO4 batteries.

[Arellcat]

For what it's worth, the Spanish Acciona team completed this year's Dakar Rally in their electric car, finishing in 53rd place.  They had a 150kWh battery made up of six modules (each with their own charging system) and each module used Panasonic cells that apparently are the same type as those you find in a Telsa Model S.  It would be interesting to see how the battery modules were put together.

Their support truck had a battery charger running on biodiesel, and the car also had a 100W solar PV panel.

I seem to remember, from Carlton Kirby's commentary, that the 2016 entry, which didn't finish the rally on account of being late to the start of one of the latter stages, had a battery pack made of something like 2000 AA cells.