Building an EV more efficient than walking

[Saladin]

Brake upgrades...the second most important part after tyres and oft ignored in the world of DIY conversions.

I like a 203mm rotor. It's torque-y and the right side of too big to draw too much attention or become an incidental impact liability. 220mms can be overpowered for a light rider on a light bike and you can get wheel-locking issues.

The original owner and converter didn't clamp the motor in place...
I went about rectifying that and realised the next problem.

The bike has an oversize bottom bracket tube, that needed to be slieved to accept the motor spindle. Original owner did that with pressed roller bearings.



Ok so the Bafang locknut couldn't bite the frame because of the larger BB ID it was pressed into the cage of the roller bearing. This meant if I do clamp the motor it would break loose smashing into the brake line on the downtube, and pincing the hose to disable the rear brake...

The fix the owner used was to not lock the motor and when you depowered it it would fall back down on the BB and the brakes would start working again. So simple! Fantastic!

This is what the brake hose looked like after 500km of that craic...



I'm impressed how robust they are.

This is a torque arm required situation.



Custom fabrication, using the original Bafang locknut, with an inner tube frame protecting, damper slieve.

See how that works?

[Saladin]

The original brake pads were expired, the dot 4 was passed it's best before, I stripped the refill port screwhead trying to open it and I had a very sorry looking rear brake hose. ...What's that? Quad piston Shimano's on sale?



Boom!





Change the calliper spacers, mount the callipers, change the rotors, run the lines, mount the levers, bleed the system. Simples.

203mm front and 180mm rear. I rather not undersize the rear rotor but a 203mm won't clear the chainstay.
A lottov bike builders put smaller rotors on the rear because it's ony 30% of your stopping power... ...I don't understand how it should warrant a lower spec by that logic...besides I use the rear for steering more often than stopping.

For all my other bikes I just upgraded the rotors and pads and renewed the hydraulic fluid. My hardtail eMTB has more stopping power due to it's lighter weight & sintered pads despite only having dual piston tektros.

Fun bike for a 6th bike.
If I could only have one I'd stick to the hardtail. It's more efficient, discrete, better at everything above 0°C, tyres cost two thirds less and there's more options & the big one: suspension; it's got better road holding.

I might go tubeless on the fat tyres with a magic puncture fixing potion inside the tyres if the new tyres are getting penetrated. I can't help but notice the best tyres I could get affordly have a lower puncture protection rating than my hardtail and aboot 3 times the contact patch...

[Saladin]

I take it back. Hohoho...new favourite boike! after 500kms..
Handles a lot like a motorbike, loves to lean and be counter-steered.
Once I put aside my intrinsic desire to bomb it downhill. It's an astoundingly capable machine...just not at this..




Roughly 30W per km...not massively far from my hardtail annabout 5kmph slower.

I'm coming around to the no suspension thing...it's lower maintainence and more reliable...and not for bombin' it...
Suspension seat is a nice compliment to air volume.

Only one puncture so far on the new twice as nobbly Winter tyres; kindov deserved it...I was ploughin' through thorny scrub on a disused forest track.

What it can do that the rest can't is climb a 45° hardcore loose pack forest fire break and get to places like this...



and this



I've named her Sherpa

[Saladin]

Honourable mention accessory is this lighting kit.



2 high output front lights with horizontally shuttered dipped beam optical projection. Perfect for road use. Mentally bright, very punchy. I'd still recommend a lid lamp though because we do often need to point the bike one way and the head tuther. Funny how on a bike you go where you look and without a lid lamp you have to look into the pitch night and go there until the front of the bike turns to meet it.

The lighting kit plugs into the bafang harness on slim waterproof connectors.

The tail light is a combined indicator/hazard lamp/ brake light & tail light.

Each front lamp has an integrated horn too..they're right obnoxious when you go stereo!

Used bike with questionably installed kit, carrier & spare tube: €700
Collection/delivery €100
Brakes: €80
Tyres: :€120
Bars: €45
Grips: €30
Seatpost Adapter: €15
Linkglide Groupset + 11spd Chain: €120
Lighting kit: €80
Replacement Thru-Axle: €50 ( because Cannondale!!)
Replacement Derailleur Hanger: €25 ( because Cannondale!!)
Better Display: €80
Half-Twist Throttle: €20
Gear-Shift Sensor: €20
89mm Crank Arms: €30
100mm Stem Riser: €15 (geometry compensation for shortened cranks)
Mudguard: €15 (bought one, made one...still a mite undersized..)
Kickstand: €15 (undersprung rattly shyte and already broken)

Bar Mirror: {€10: Adapted a LHS from the spares bin}
Suspension Seatpost + spring saddle: {€110: One fits fleet}

€1560

I'm running dual batteries and replacing the 48V 24Ah one she came with for a 52V 30Ah triangle.

You can pair a 48v and a 52V across a battery combiner (dual ideal-diode). They cascade discharge which mean it's not really parrallel it's sequential with overlap and the higher voltage battery will probably trip LVD on it's internal BMS before you get home.


Your mission should you choose to accept it; find a(n electively restricted for off-road use) store-bought machine with a 1kWh non-proprietary battery, a 160Nm torque programmable motor that's transferable to another bicycle, quad piston 203/180mm hydraulic brakes, a replaceable steel groupset with a rivetted casette & an e-bike rated chain. Nobbly Winter tyres and a comprehensive lighting package for oh..less than €5k...! Good hunting!

If I do 15 000km a year at 30watt-hour per km.
that's 450kWh per yer transport fuel.
One quater of that is import: 113kWh x €0.40 = €45 per year transport fuel cost.

+ a €30 chain (varies) every ~ 1200km (€375)
a rear tyre every ~ 3000km (~€125)
a front tyre every ~ 10 000km (~€42)
20L of chain degreaser annually (~€200)
2L of chain lube annually (~ €100)
a new cassette every ~5000km (€90)
Wheel hub bearings...vary whenever they get crunchy..: every 10 000km?.. depends on seals and riding conditions

Annual cost of ownership:
Ballpark €0.07 per km.


With a heavy bias on off road. I hardly ever come home without gravel grit and/or mud in my drivetrain...having tortured my tyres scrambling over coarse hardcore.

Funny thing about car ownership; is that costs money when they're not moving too.
Has anyone ever gotten an insurance refund or a tax rebate for the days they didn't drive?
Besides; if I can't fix it I don't own it, I'm just renting.

[Saladin]

Here's a few mods to help.
4.2V x 14cells series = too bleedin' high with no bejaysusin' overhead..



and I'd rather 2000 cycles to 85% SOC rather than 500 to 100%




Derate!!!!!!!!

See that potentiometer that says VR1 for voltage regulator 1?



Twiddle it until it outputs 4.1V per cell.



Presto that batteries "lost" 15% usable but it'll last 4 times longer and it's waaay less likely to burn your house down.

There's another way to mod. this externally.
My most recent battery charger didn't have that very convenient turny trimpot. I used the series Vf drop of a bridge rectifier instead.



Charger positive out connected to DC- with DC+ output feeding the battery charge port positive.

Something like this with the middle two legs not wired.



Marmalade it onto a lump of copper or aluminium. If it runs for 30mins at full load and touching it doesn't burn your finger then the heatsink is the right size.
The higher the Vf the better for this application, which is a lower-end pocket friendly type, in this case as we're aiming for a float current voltage drop aggregate of 1.4V at 58.8V.
The charger charge complete green LED even still works...I'm guessing that's driven by opposing voltage tail current threshold.
Sure! You can just use two or more series diodes instead.