Commuter Build Review

Hi all,

I've been irked by my long driving commute for a while and looking for an alternative. I work at a battery company and was recently given a nice Samsung pack (48V, ICR-18650-22F cell). The pack is super oversized (Spec) but it fits nicely in two pieces into a pair of panniers. Here is my spec:

Weight: 160lb
Distance: 22mi one way
Terrain: Bike paths
Speed: <20mph but more is always better
Budget: Negotiable, estimating $700
Wheel: I'm looking at 26" disc brakes
I've already purchased a MAC500W rear motor and single speed freewheel with 9 FET controller and 10T windings.

Couple of questions on the bike choice. I have a 2009 26" Raleigh Mojave 4.0 that I can use. Will this aluminum frame hold up with a single torque arm? I'm considering selling this bike and purchasing another. I'd like something with a more comfortable setup and came across a nicely priced Raleigh Detour (Link, but it has the same aluminum problem. So my main question is exactly how quickly will an aluminum frame break if I'm using reasonable power limits (~1000-1200W)? Is it really required to use steel frame bikes? They're just difficult to come by.

Other than that, I plan to get some rear racks and panniers and some 12V LED lights (purchased DC/DC already) to make it a finished product. Any other suggestions?

Thanks

At 48v I use 2 torque arms, they're cheap enough.

That battery you linked to is 45ah and 37lbs. 100mm wide, That is a huge battery, where are you going to put it? If you already have everything, why not run it, see how it rides. So much of ebikeing ends up being upgrading anyway, might as well get started on a baseline, good luck

Use a couple of steel torque plates and you'll be fine. I don't know what kind of speed you'll get with the 10t mac, but it should be at least 20mph. You should be able to make your 44 mile rt commute on a single charge with no problem with that battery pack and have plenty juice left over.

I'd be concerned about the size of the battery also. The bulk and weight makes everything harder. My Ping 48v 20ah is about 22lbs, and I wish it was lighter. My bike is too heavy for kick stands, the battery broke The rack I was using (twice), etc. Do you have a trailer? Maybe this is a good power assisted trailer scenario?

The spec sheet rates the nominal discharge rated at 17.5 amps, or 840 watts, max at 35A. But I saw a spec sheet for the cells, that say they are rated at 2C. Which for that pack would be 90 amps, or 4320 watts. So... why are they so different? If your pack is intended as a low watt power supply, maybe something is not suited for ebikes? Maybe the BMS?

Colin

I've ripped the pack apart and done lots of cycling testing on it already. It's designed for long life (+5yrs) in telecom space. That's why it's rated for so much lower than the 2.2C rate. It has very poor cooling, so if run at 1C continuously it would get very hot. I think with the 30A controller I won't have any thermal issues or life issues. I know it's not the perfect battery for ebiking, but I just don't have another 300 or $400 I want to spend right now. I'll be able to split it into two equal pieces, but I am weary of the weight. Alternatively I can use it as a 24V pack with only have of it.

The BMS has all of the nice safety features (3sec over current, balancing, etc.) and won't have any problem with the currents.

Can anyone point me to cheaper torque arms? The one I purchased was $40, seems very excessive.

http://lunacycle.com/hub-motor-parts/

If you have a angle grinder or better tools, make your own. Go to the nearest metal supplier and pick up a small offcut piece of steel plate for next to nothing. Mark it up on your dropouts and whatever screw holes you have nearby and grind away. Test fit the openings lots and you can have super strong torque arms that are nearly built in.



These are overkill for the Mac but maybe ~ 1/4" for you.

Ah, that is a pretty DIY fix. I'll give it a shot. With a good set of torque arms on a rear motor is the rest of the frame fine? Can I safely go with the Detour and get a more comfortable ride?

Thanks for help guys.

The motor itself won't break a frame but the extra weight your carrying will be harder on it. But if your not doing big drops you'll be fine.

Be sure to invest in think Kevlar tires, and thick puncture resistant tire tubes.

Nothing more annoying than having a flat on an ebike.

If you are buying a new bike, consider a longtail cargo bike, which will handle a bit better with that much battery weight in panniers.

Also an option, sell off the huge battery to somebody who needs one that big, and then buy a battery that only weighs 15 pounds or less

Meanwhile, one good properly installed torque arm will do.

Thanks dogman dan. A cargo bike (Big Dummy or Yuba Tuba) is in the future. I have to prove to the wife that I will use this thing consistently before we get that. I promised my boss I wouldn't sell the pack for gain, so I'm pretty much stuck using it. Plus with 44mi round trip I'm going to need a decent sized pack anyway unless I want to charge each day.

Thanks for the help. I've decided to stick with the Raleigh for the front suspension. Now I just need to buy the parts for the single speed conversion. I don't want to mess with shifters that can break.

aomagman78 said:

Other than that, I plan to get some rear racks and panniers

Click to expand...

I echo the others about a standard bike rack - there's no way that will last. The bolts will shear off if the welds don't break.

You need rear "suspension" - the easiest is big fat low pressure tires, but these might not have enough travel/ give.
Next step up is dumb old rack & panniers with big chunks of urethane foam, or bubble wrap stuffed in the bottom to cushion impacts from your batteries.

Next harder is to make a is custom battery rack that floats. With that much weight you'd need a really solid pivot with real bearings connected really solidly to your seat stays.
Scrap yard hatch struts can actually have gas pressure added or reduced. You can also set it up to play with the angle of attachment to get more or less pre-load.

A trailer just for the battery with an Anderson disconnect would be a lot easier.

That's interesting Foster. I hadn't really considered the impact forces on the rear mounts. I'd prefer to not get too crazy with struts just yet but it's obviously something I need to address. I'll have to get creative with how I pack the batteries, like you mentioned. This is also an option I'll look into.

http://www.amazon.com/dp/B0154OMGIK?psc=1

Cool looking rack, but I wouldn't use it, because:
- that's a lot of force on your seat post and frame.
- I doubt the adjustable stays would hold over bumps (given your battery weight)
- the middle of bike frame tubes are the weakest - why focus the force there?
- the rack doesn't make sense. Seat post mounted racks are for bikes with rear suspension. But then you can't mount the support stays. So what kind of bike is this intended for?

For a rear rack, for your weight, get a serious touring rack, preferably steel. Or have one made. You want to build this bike to last, right? Not just get by for a few months. I know my mountain bike feels weird with just a few jugs of milk in the panniers. Get some dummy weight and try it out before you start buying and building. There's my free advice.

If you must use that battery, a trailer may be cheaper than a good rack and bags.

Recharging often is better than less often. If a trip takes more than 10% of my charge, I tend to top off the pack again.

Colin

Thanks everyone. Sounds like my big oversight is the battery weight and how to carry it. Just for ease of storage/locking I really don't want to use a trailer. I'll look into a sturdy rack. Or possibly beefing up an existing one. It's an interesting problem to have for sure. I guess I hadn't really considered 40lb to be too heavy but you're right that the impact will make it feel much greater. I'm quite surprised how much additional weight is in the battery pack since 280 18650 cells are ~12.6kg and the pack is at 18.5. That's a lot of extra mass in conductors.

I'll do some searching on here to see how other people have solved this problem.

1JohnFoster said:

aomagman78 said:

Other than that, I plan to get some rear racks and panniers

Click to expand...

I echo the others about a standard bike rack - there's no way that will last. The bolts will shear off if the welds don't break.

A trailer just for the battery with an Anderson disconnect would be a lot easier.

Click to expand...

Just to join in on the consensus, I don't even have my battery in my rack; but I do use it with some pretty heavy loads as it is my sole transportation. That being said, the "touring" rack I got hasn't made it a year without parts breaking. I am going to replace this Aluminum touring rack with a steel one and see how it holds up.

Actually,a bob type trailer might be your best solution to carry 40 pounds. Cheap imitations of a bob trailer on amazon, mine is holding up fine in it's second year.

lester12483 said:

Be sure to invest in think Kevlar tires, and thick puncture resistant tire tubes.

Nothing more annoying than having a flat on an ebike.

Click to expand...

Try having a flat on a KMX trike


Which brings me to a good point. At 22 miles I think you'll be better off with a trike. The advantage of trikes is that you can cruise at a higher speed with less resistance hence you don't need such a big battery pack. Also your position is much more comfortable than a mtb.