http://www.ebay.com/itm/A123-SYSTEMS-AHR32113-ULTRA-A-3-3V-4-4AH-High-Power-L...


Could I use 4 of these cells running parallel?

http://hobbyking.com/hobbyking/store/__26054__ZIPPY_Flightmax_4200mAh_4S2P_30...


Something like this is a pre-made pack. Which for 40 dollars is pretty cheap. It uses lifepo4 packs and can handle a maximum discharge of 168 amps.

True that a rc application battery is not ideal for a motorcycle but since I am a electrical engineering student im wanting to do something interesting on my bike. I want to build a portfolio of projects. Im currently doing led lights for my bike. In the process of soldering atm.

Dave wrote on 05/15/13 at 11:21:15:

While I agree, I don't see any reason why you couldn't.
The caveat here would be that RC batteries are made for "attended" charging.  And at some point you're going to need to balance the battery pack.

Whereas the earthx battery has this functionally built in.

You would need 2 of the RC packs as opposed to the earthx battery for the same capacity.  Mod's for the hook up and balancing and you're back to the cost of the earthx.

I suppose the idea of assembling a battery from several smaller batteries has the feature that it can be "distributed." That is, with suitable cabling, part of the battery could hide under the tank, part under the seat, part on the emissions bracket, and so on. That way there is no single bulky piece to hide. The drawback is that the cables have to be able to handle the current. Perhaps they could be run through a piece of metal electrical conduit, bent and painted to mimic a frame tube.

The claim is that although a Lead Acid battery might be rated at 12 AH, the battery can only provide about a third of that power, and as you crank the available voltage drops off steadily.  THe LI-Ion batteries are supposed to be able to deliver all of the AH and the voltage does not drop off until the very end....and then it plummets.  Their claims are that their 12AH Li-Ion battery is equivalent to the performance of a Lead Acid battery with a 12AH rating.  It is kind of an apples to orange comparison.....however the result is that they will both crank an equivalent length of time.

The bottom line for me is that if your bike is tuned well and you don't leave your headlight on accidently.....the EarthX battery does a great job and starts the bike easily.  I only ride in temperaturs above 50 degrees, so I can't tell you what happens if your bikes sits outside and you ride when it is 10 degrees.  When I hit my starter button my bike starts in less than 3 or 4 turns......I probably could use a much smaller battery and still be fine.

Here is the supporting propoganda from EarthX.

Lithium batteries voltage remains relatively constant while discharging, while voltage for a lead-acid battery decreases. A lithium battery can use 100% of its storage capability (measured as Amp-Hour, Ah), while a lead-acid battery typically only uses 30%. Lithium battery’s cranking power will not drop-off, and it will crank your engine longer. But when the lithium battery runs out of power it does so abruptly. Just like your lithium powered hand tools.  LiFePO4 cells by the nature of their chemistry are 3.3 volt. 12V lithium batteries, like our motorsport batteries, are created by using 4 cells in series (technically it is a 13.2 volt battery). The lithium cells (in series) in a 12V battery pack diverge in both levels of charge and capacity with each charge/discharge cycle. This condition reduces the performance of the battery (reduces capacity) and can lead to overcharging or over discharging a cell. A cell is permanently damaged if over charged or over discharged just one time. In the case of overcharging, cells can rupture, and the entire battery will need to be replaced. Inside every one of our batteries is a microprocessor Battery Management System (BMS) that monitors the charge level of each cell and balances the charge when needed, protecting the cells from overcharge or over discharge