I've seen on various sites people touting the A123 batteries for bikes. Now, I've harvested these from DeWalt power tool packs for model airplane use but didn't know they were used for bikes,too. I do know the internal resistance is pretty low. An 2p4s pack would have 8 cells and plenty of power to start the Savage. The advantage is supposed to be less weight. The nominal fully charged voltage is 14.4 volts which is about the same as a 6 cell lead acid battery.

Would these be an advantage for a custom build? The dimensions for one advertised motorcycle specific battery are  4.3 by 2.25 by 3 inches and the weight is less than 2 pounds.

Anybody here try these for the Savage?  I 'spose I could take a couple of 4 cell packs that I've already made up for model airplane use and kludge them together in parallel to see how or if they can spin the motor over on the bike.

John in Kalifornia

Don't forget if you build your own pack, you will also have to build in a charge controller as well. The stock charging system is not intended for anything other then lead acid type batteries. Trying to charge A123 or any other Lithium type battery without a proper charge controller built in is a ticking time bomb.

R.F.

II think there is some confusion here. The A123 batteries as used in DeWalt power tools and electric vehicles are lithium iron phosphate (LiFePO4) chemistry. This is not the same as the lithium polymer batteries that cause laptops and cell phones to catch on fire.

The charge voltage for the Lipoly batteries is 4.2 volts per cell. This fact results in a rather inconvenient charge voltage of 12.6 volts or 16.8 volts for 3 or 4 cells in series, respectively. The A123 cells have a 3.6-volt charge level so for a 4-cell pack the voltage would be 14.4 volts. This is very close to the voltage regulator setting for 12-volt lead acid battery powered vehicles.

The A123 batteries have a very low internal resistance. That means they can put out a lot of juice, just what we need for starting. I have a clamp on Sears amp meter that I’ll try to use in conjunction with some other test equipment to see how much the starter actually draws and how low the battery voltage drops. Maybe ground out the spark plug and crank for a few seconds to get a steady reading.

If the battery can put out enough juice to turn the motor over and still have a high enough voltage to run the ignition it might just work. One could hide the battery under the seat or some other place and have more room for a bigger K&N filter or just free up some visual space behind the motor.  On the other hand, one still needs to find a place to mount the regulator and starter relay. The battery box is convenient for this.

More later after I do some rewiring and some tests.

John in Kalifornia

You are right as far as it goes. Supposed to charge at a constant current til the battery gets to 3.6 volts then leave the voltage the same and the current will taper off as the battery tops up. The max charge rate for A123 batteries is 5C which for a 4.6AH would be 20 amps or so. These are very tolerant of high rates in both directions. I doubt that the Savage charging system would be able to put out enough amps to over charge it.

We are warned not to use a car battery charger on a motorcycle battery. I really don't think that the sealed lead acid or AGM batteries used in motorcycles would tolerate as high a charge rate as the A123  batteries. If one was running without the lights on and nothing but the ignition as a load the battery would charge pretty quickly and the current would drop fast.

I agree if it requires modifications to the electrical system it would be better to stay with dedicated m/c batteries.

And make sure you have some way to operate the compression release manually for push starting.

John

Oldfeller--FSO wrote on 05/26/12 at 19:33:49:

That is very true.  But there is still one big pitfall to any Lithium type chemistry formula battery still on the market be it the older "un-safe poly type" or the newer "safer" types, is colder weather issues.  Lithium chemistry still does not perform in cold weather period. So it might turn out to be something that can be used for a warm weather only bike rider, but for those that ride year round it can't be used.