Tuesday, July 27, 2010

Battery LiFE Po-or

Sometimes, new technology like that from electric cars and bikes provides an interesting advantage for our old, existing technology. The KLR is typical of many motorcycles with a smallish, flooded lead acid battery that works OK for a while but seems to need water constantly and, even though I keep it warm and charged through winter, lasts 2 years and then dies.

I have been laying out $50 every 2 years for a while now, so I got curious about what else is out there. I found more expensive Yuasa Micron batteries ($70) and AGM sealed batteries ($100 - 120), but they are still just lead-acid and I've heard that the life improvement is little or none.

Then I came across the Turn Tech battery. It uses Lithium Iron Phosphate (LiFE Po) chemistry that is made up of sealed cells with very low self-discharge (<1%/month). The weight savings are amazing. My lead acid battery weighs almost 11 pounds on my scale. The Turn Tech, less than 2 pounds! You can think of that as a 9 pound savings or an 82% weight savings. That can't be bad.

Even more interesting, the Turn Tech is rated at 250 amps at 70 deg F. That's plenty of power to start my KLR which spins up easily every time.

How about life? This graph from the Turn Tech website shows cranking for 18 seconds per start. My bike usually starts in about 1 second, maybe 3 seconds on a cold start. Assuming this curve stays linear, even at 18 seconds cranking, this battery should last more than 9000 cycles. If I started the bike 4 times a day, every day of the year, that would be about 6 years. In reality, I don't get to ride every day and my riding season is only about 7 months per year. At that rate, I am hopeful that it will last 6 years or more. All without watering. Yeah.

The cost of this 5 Ah battery is about $160 or about 3 times the cheap, flooded lead-acid. Its worth it for the no maintenance, weight improvement, and just to know you have something "high tech" in your bike. If it lasts anything more than 6 years, I'm ahead of the game.

Of course, nothing is perfect. You can't put this on a bike where there is a constant current drain from a clock or other electronics. My KLR is dead as a door nail when the key is off, but this thing is only 5 Ah capacity, so it will discharge from a current drain a lot faster than the 14 Ah battery its replacing. If you do let it discharge, its a one way trip to a 2 pound paper weight. This chemistry doesn't come back from a deep discharge. They also don't recommend it for bikes bigger than a 650, although Turn Tech will make you a custom battery for special applications.

I'm such a geek. Thanks Turn Tech.

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