[Elecraft] Re： Li-ion battery pack for KBT2, K2

[Johnny Siu]

Hello Leigh,

Thanks for your very informative reply.  My next step is to cross the border to source LiFePO4 cells in Shenzhen, Mainland China.  Today, China becomes the major manufacturer of various types of Li-ion cells.  The price is so cheap that the same as SLA.

BYD, one of the up rising battery car manufacturer, has its major manufacturing plant in Shenzhen, Mainland China.  Their share price has been double in the past two months.

73

Johnny Siu VR2XMC




________________________________
寄件人﹕ "Leigh L. Klotz, Jr WA5ZNU" <Leigh at WA5ZNU.org>
收件人 Johnny Siu <vr2xmc at yahoo.com.hk>
副本(CC) Elecraft <elecraft at mailman.qth.net>
傳送日期﹕ 2009 年 7月 26 日 星期日 下午 2:57:44
主題： Re: [Elecraft] Li-ion battery pack for KBT2, K2

Johnny,
Some have done this, but the Li+ cells are prone to catch fire, so it's risky.  SLA is well understood and less risky.
They can catch fire when over charged, of course, but also when over-discharged.

Some people are reporting the A123-manufactured Lithium Nano-Phosphate cells are safer than the Li+ and LiPoly.
They don't catch fire when over-discharged, for example. 
Unfortunately, they don't quite fit in the K2 battery case, at least now in a way I can figure.  There are also non-A123 brand LiFePO4 cells which you should be able to get in HK easily.  These are 3.4v and a better fit (4*3.4=13.6, max 14.4v) for 12v radio electronics than the ~16VDC full charge of Li+.  They are thought to be safer than the Li+ cells, but the no-name brands don't necessarily have the same testing as A123 brand, so again it's more of a risk than SLA, though less of a risk than Li+.

LiFePO4/A123 have excellent power density, and can source 60 amps easily, so they must be fused close to the pack.
They don't have as good energy density as the Li+ technology, but with the K2 that's less of an issue since its RX draw is so low.

Leigh/WA5ZNU



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