Hub battery

[mark swenson]

Has anyone every put a battery together in a hub motor case? Or fabricated a case that that could be used in this manner? I know Wavecrest did this with their bike...it would be nice to do this for other bikes.

Anyone have an idea of how hard it would be to build something like this? Could Battery Space create a battery that would fit into a hub?

 

[Link]

An interesting proposition. I suppose, if you were to find a big, dead hubbie, you could trim out the stator and fill it's space with batteries. The wiring is already there, so it would probably take only minimal effort.

Obviously, you wouldn't be able to fit much in there, but it would make for a pretty stealthy bike.

 

[andys]

A fellow in Canada had some bikes with a older style LION battery in the rear hub. I looked into ordering just the hub and battery, but the costs was too high for what you got. Like $800 for a 7ah battery set up. I also had concerns about the battery taking a beating down there in the wheel, spinning at high rpms and getting bounced around. I wondered about the wiring as well. Don't they have to have some sort of brushes to transfer the battery output power out of the hub if it spins? How else could the hot leads come out of a spinning package? That seems to be asking for trouble in the long run.

My solution was to get a very compact 36V 10.5AH LIPO from E-bike.ca for $300 less that had 50% more capacity. At 6 pounds and measuring 2.5 X 3.0 X 9.75 inches, it can be attached easily to the frame area of just about any bike. Ebikes.ca has had good luck with reliability on those compact batteries so far, and tests every one before shipping them out.

http://us.itselectric.ca/product_p/37v-lithium-polymer-10.5ah.htm

 

[Toorbough ULL-Zeveigh]

if you axe nice, perhaps these guys will sell you one.
NiMH only tho.
And yes, hub batts will always have a price premium attached cuz they come packaged in a well designed enclosure & BMS.
http://e-ms.us/lawenforcement.html


You have to keep in mind that there's not a whole lot of volume inside a wheel.
So it's not worth all the effort to roll your own, but I'm actually a proponent of a battery in the hub.
Been riding with one for three year & hop curbs multiple times on a daily basis.
The batteries bouncing around has never presented a problem & are probably more protected than a pack flying off the back of a rack at high speed.

The E-MS & WCL hubs are 12" dia. (compared to the X5 10") & even with the bigger hub they can only hold around 300 Wh which is barely adequate capacity for a first time/entry level ebike but not for anything hi-power.
I bought a dead Wavecrest hub-bat wheel for a hundred bucks & there's plenty of empty space inside surrounding each of the 30 NiMH D-cells, which I'm presuming the space is left there for cooling.

I figure by filling that empty space to the brim coupled with utilizing newer high density 335Wh/litre NiMH in place of the older original 200Wh/litre, I can squeeze in a half kWh of NiMH max & hope that internal heating will be less since I'll have a lower resistance pack made up of parallel strings that won't require as much convective cooling.
Alternately going with the highest energy density chemistry available to me, i.e LiCo, the most I could wedge into a 12" hub would be one full kWh, which is nothing to turn your nose at to make use of valuable free real-estate that's in short supply on a bike.
I hope that gives you some realistic expectations of what's possible if you decide to make your own.

I like that a hub-bat gives *you* the freedom to choose how to best utilize your payload space on the rear rack, between more battery or groceries depending on your requiremets in a given instance.
The hub battery is an idea ahead of it's time, once batteries become available with even just a doubling in energy density of the current crop then I think maybe you'll see more manufacturers package their ebikes this way.

And don't let anyone tell you about unsprung weight killing the whole idea, just like they'll tell you about the gyroscopic effects of a spinning mass, they have no idea what they're talking about.
The battery hangs onto the axle & don't spin, same as the STATor of a hub motor, it is STATionary.
The Wavecrest hub battery is around 15 lbs which up to that weight is a non-issue, altho I wouldn't want to go much above that.
I can dig up for you if you can't find it for yourself a recent posting on the power-assist forum by the chief engineer from E-MS a good explanation about the tradeoffs involved in unsprung weight & why he thinks a hub battery's low c of g is an optimal design choice.

 

[steveCA]

My first e-bike was a Wavecrest 750X, and I really like the way it handled. The weight distribution was just about perfect. However, the bike was underpowered, and lacked any kind of range out of the front hub battery. So, I swapped out all the Wavecrest components, everything except the frame. I went to the C-lyte Phoenix Cruiser kit, without the lead. I purchased two 15 AH LIFEPO4 48v and I made my own battery mounting mechanism that I believe provides almost as good a weight distribution as the Tidalforce had.

I made the battery boxes and mounting brackets in my garage shop. The aluminum was purchased at a scrap metal dealer for less than $30.

I now have 500 miles on the rig (I use it daily for my 20 mile commute), and it is holding up very well indeed. I do not have to charge the system at work. It makes the full 20 miles at top speed and up and down some pretty tough hills. I plug it in at night and its ready the next morning. The commute uses just over 1/2 of my battery capacity, about 17ah.

I did have to make some adjustments in my riding style. I quickly discovered that 30 lbs of batteries so low on the front axle means that I have to shift my weight a bit more aggressively to get the same cornering result. After the first week though, I had gotten used to it and now the bike seems pretty nimble. I love the speed and range... 30mph for 30miles... Actually, more like 25 miles with zero pedaling, and an easy 35 miles with a little leg work.

Steve