Power Hungry…

April 4, 2012

Wanted – 2000W 10″ hub motor with drum brake

I’ve been away from the blog for a while, and some of you might have been wondering if I’ve just run out of things to do to the bike. I’m happy to report that that isn’t the case by any means. I’ve been painfully aware that I still have one weak link in the system of an otherwise great bike: Despite upgrading to a vastly improved LiFePO4 Lithium pack and the Lyen 12-FET 4110 controller which can delivery as much power as heat dissipation will allow, I’m still stuck with the piddling little 1400W hub motor that originally came with the bike.

Amazingly it seems perfectly content with the 3.6KW that it’s being fed by the Lithium pack/controller system, which delivers 80V at a rate of 45A in its current configuration (I dropped it from 50A when I switched from the lower voltage SLA bank). Though I’d like to ramp it up to 60 amps, the phase wires start to get troublingly hot if I run it at anything over the existing current. This is essentially the bottleneck in the system, now; though motors can take a remarkable amount of punishment and cheerfully operate way beyond their nominal specifications, the narrower gauge wires will run hotter and less efficiently, and there will come a point where the phase wires will just melt (as detailed by to an unfortunate owner on the Electric Motoring Forum).

In recent months I’ve therefore been shopping around for something that packs a bit more power. Hub motors come in a range of sizes and powers, from feeble, 300W affairs to help people cycle up hills, right the way up to 6KW beasts that you could make a drag racer out of.  Disappointingly though, it’s proven less than easy to get hold of the 2000W motors that now come as standard with many of the recent electric scooters. Typically they only become available when someone is breaking a 60V UK Eco scooter or something else equiped with the better grade motors, and this is how most of the e-biker community seem to get hold of theirs.

Even though the internet seems to be choc-a-bloc with adverts and illustrations like the one above, mainly from Chinese vendors and Alibaba-type wholesalers, actually finding someone who will sell one is a different matter entirely. I wasted the best part of a month negotiating with a “Robert” from a website that claimed to order motors custom-built direct from the factory. The guy went to the trouble of setting up a Paypal account to take my order, and duly took $400 from me for my order for a 2000W 10″ hub motor with drum-brake. I’d asked for it to be wired for high RPM (‘fast’ rather than ‘high-power’), as I have all the power I need but wanted more top speed.

…unless you want to actually buy something

Two weeks later I was wondering where he’d got to and why I hadn’t heard from him or received any information about shipping. I duly contacted him, only to be told – without explanation – that he wouldn’t be able to get one after all. He duly refunded my money but I was hopping mad that the idiot would put us both through this ridiculous charade via what turned out to be a baseless, vapourware website. If you see the logo above, accompanied by an exciting looking catalogue of electric bike parts, then steer well clear…

I’ve had an equal lack of luck with the Alibaba and DHGate traders. Search results throw up reams of traders claiming to deal in these motors, but enquiries so far have just amounted to “sorry we don’t actually sell them, we just pretend to”. Presumably it’s so that they can get my email address and send me spam about batteries for the rest of my life.

So for now I’m keeping my ear to the ground about any bikes that are being broken for parts or even sold whole. If one comes up that’s not to far away I can hopefully land myself with a suitable replacement to the existing motor.

16-FET Controller Upgrade

Once that’s been taken care of, there’s the next and final option regarding controller upgrades, which is to move from the 12-FET controller that I have at the moment to a 16-FET equivalent. More FETs mean I can pull more power, and with a suitable motor get me a better top speed. There’s also the option of moving from a 3.50 tyre ‘thickness’ to a 4.0, which will increase the diameter of the tyre from 17″ to 18″ translating some of the power into higher (about 6%, theoretically) top speed. If I could find a vendor who can sell me a hub motor to order, I could even move from a 10″ to a 12″ diameter hub to get the top speed up even more. The rear wheel arch seems to have more than enough clearance to accommodate an extra inch of radius above the axle, and even if it doesn’t I could just change the rear shocks for slightly longer ones.

I’ll keep you posted as my quest for a better motor goes on…

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