Smallest battery that will still turn starter?

I've been reading through a lot of the "cleaning up the triangle" threads. I finally found a titled frame for my next CB550 project and it's already been de-tabbed, so I guess I'll be going a little more custom than I originally planned.

For a couple of reasons, I'd like to be able to keep the electric starter. I can mount the battery on the swing arm and, possibly, depending on size, under the seat/hump. The seat I have planned has a somewhat lower café hump that usual.

I was talking to a friend about his kick only Harley, and he's running an 8 cell Ballistic. He says his friend with a 74 cu. in. Harley has the same battery and it works fine with the "electric thumb".

Is there a battery that is small enough to hide and still run the starter?

check out ebay for lifepo4 batteries. they are small - very small - and pack a lot of punch. generally speaking, you can use one with HALF the recommended Ah for lead-batteries. i have a 7Ah-battery in my bmw r80, whereas the original big bmw-battery had 18 Ah. you can start for minutes and minutes if you like, without the lifepo4 giving up the ghost. notbhing else comes close

LI-ION batteries (including the PO4 designations) have a very high energy density, so they're lighter and smaller than most other battery types. They also have a very discharge amperage, meaning that small batteries can do a lot of work (such as turning a big starter motor), but only when warm. Discharge capacity of LI-ION drops significantly when temperatures get low.

Unfortunately, an Amp Hour is an Amp Hour and the smaller batteries (while being capable of doing big jobs), can't sustain that level for long.

A four cell LI-ION is usually good for two, maybe three, starting attempts on a bigger bike and so I only recommend the four cells on kick-only machines. Under 500cc with electric start is an eight cell job, and over 500cc is usually a 12. Liter+ bikes may even want a 16 (especially big twins).

So while you can used a reduced rating battery for your bike, it has little to do with the materials from which the battery are made and more to do with your requirements for your machine.

How about this for a '78 Yamaha xs500 twin?:

http://www.ebay.com/itm/Honda-PCX-125-150-WPS-FeatherWeight-12v-8-Cell-LiFePO4-Lithium-Ion-Battery-/271276369437?pt=Other_Vehicle_Parts&hash=item3f2954e61d&vxp=mtr

Thanks

Looks good to me. Check to make sure the positive and negative terminals are on the correct side for your application.

anyone find the dimensions for that battery? I can't seem to find them anywhere