Building an EV motorcycle. Batteries: Need opinions.

[TurnNBurn]

Alright, so I've narrowed the batteries and vendors down. I have a question. I'm aiming for these: CA40FI 40Ah CALB Lithium Prismatic Battery EV LiFePO4 Cell

40 Ah CALB batteries. I was going to get 23 of them. However, for about $25 more there's a comparable 60 Ah battery. Is the extra 20Ah really worth the extra $25 per battery, bringing the cost up from $1265 to $1817. Roughly $500 for extra 20Ah. I know Ah will aid in the total range, but so will gearing, controller programming, weight management, aerodynamics, and more. How far do you think 20Ah would get me assuming a constant speed of 45 MPH?

In summary, I guess I'm just looking for a cost benefit analysis between the 40Ah and 60 Ah.

[Ryland]

The 60ah batteries are a better deal, if your motorcycle ends up using 150 watt hours per mile (high end of what people use, like if they are going fast) then you will get around 20 miles range with the 40ah pack and 30 mile range with the 60ah pack, assuming you are going slower (less then 65mph) then you will get more miles per watt hour, some people say as many as 75watt hours per mile, so your range at say 45mph might be 40 miles with the small pack or 60 with the large pack.
at $55 per 40ah battery or $79 per 60ah battery, the large one is the better deal.

23 cells is an odd number...

Your weight per watt hour of battery is also going to be better with the larger cells.

[Daox]

Also, 60Ah batteries are going to handle 'fun' discharge rates much better than the 40Ah cells. I think the 40Ah CALB CA cells have been tested at 10C discharge (400A) and they can handle it. But, the 60Ah cells are only at 6.6C at a 400A discharge. Therefore you'll have less voltage sag and more available power. It will also be easier on the cells and improve the life of them because you aren't 'beating' them as hard.

[TurnNBurn]

Originally Posted by Ryland

23 cells is an odd number...

I just said 23 for price reasons. I'm looking at maybe 24 or 25, however I may fit them on he bike.

From the sounds of it, I think I'll shoot for the 60Ah batteries, maybe even higher just because now I'll need o start saving some money.

-edit-
A123 pouch cells? Are those worth looking into at all?

I'm looking more at the a123 pouch cells. Are they really worth the consideration? Are there any open group buys you guys know of? Or even better, are there any a123 packs pre-assembled I could buy?

[TurnNBurn]

Update: got the motor mounted and will post pictures of the stripped frame and the motor mounted. However, the rear sprocket is stock and the chain doesn't quite clear the rear frame. So a new 72 tooth sprocket has been ordered and that should raise the chain up enough to clear the rear.

Pictures will be posted throughout.

Also, I've settled on the battery, but in the meantime I'm buying two 12v lead acid batteries while I build the electrical systems (headlights, turn signals, etc...) and get a feel for the bike.

[TurnNBurn]

Here are those progress pics I promised. They're not great as they were taken with my phone. I'm getting some higher-res photos with my T2i later.

I'm kind of at a dead-end and don't know where to go or how to proceed.

https://www.dropbox.com/s/u6jtpg3qj2...204212_474.jpg

https://www.dropbox.com/s/gr1wc62cij...204239_768.jpg

https://www.dropbox.com/s/et499ibi10...204254_157.jpg

As you can see, I'm having issues with the chain rubbing on that lower part of the frame. Any advice on how I can avoid that? This is with the chain fully tense and with the master link inserted, but not completely clipped.

[Ryland]

You can either make a chain idler out of a roller skate wheel or you can make a slide like is common for chain tensioner out of a piece of plastic cutting board.

[TurnNBurn]

Originally Posted by Ryland

You can either make a chain idler out of a roller skate wheel or you can make a slide like is common for chain tensioner out of a piece of plastic cutting board.

*FACEPALM* A roller skate wheel. That would work. I'm going to check out my scrap metal and see what I can come up with. Thanks!

[TurnNBurn]

I actually think avoiding a chain tensioner is the best way to go, and this means I'll need to re-position my motor mount. I'm going to get a steel bar and drill some holes and move the mount up by about 1.5 to 2 inches.

[mechman600]

Originally Posted by TurnNBurn

As you can see, I'm having issues with the chain rubbing on that lower part of the frame. Any advice on how I can avoid that? This is with the chain fully tense and with the master link inserted, but not completely clipped.

Probably not a big deal being on the unloaded side of the chain. Ryland's suggestion is good. Even a simple plastic guide would be good enough on the unloaded side, the same as most motorcycles use along the top of the swing arm to guide the chain during decel.

Nice build!