-------- Original Message -------- Subject: Re: [amsat-bb] Lithium polymer batteries Date: Thu, 24 Jun 2010 12:34:14 -0400 From: Michael Tondee mat_62@netcommander.com To: amsat-bb@amsat.org

Li poly batteries are perfectly safe as long as one uses common sense and follows basic safety procedures. The fire retardant bags and clay pots are a nice extra bit of insurance but I haven't found them really necessary as long as I pay attention. I charge my batteries outside mostly or if I do charge them inside I don't leave them unattended. As someone already stated, using the proper charger is the key. With the proper state of the art charger it is near to impossible to overcharge a li poly battery. I emphasize "state of the art". A very good one called the Cellpro is made by a company named FMA and is under $100 in price. I fly electric RC airplanes and helicopters with Li poly batteries. I order them online and I have never been charged any type of hazmat fee. FWIW I've had numerous hard crashes with my heli and have never ever had a li poly battery explode or catch fire. These batteries have revolutionized RC flying. Along with brushless motors, it's a whole new world. It's now possible to fly planes of the size that used to take nitromethane or "glow fuel" powered engines with clean quiet electric power. 73, Michael, W4HIJ On 6/24/2010 10:01 AM, whiteld@usa.net wrote:

Following up on the Lithium polymer battery mention I Googled them and was disturbed to find:

-high fire risk. One seller offers flame retardant bags to put the cells in while charging them... for $25

-(as warned) high prices especially considering the more-unique balanced charger / discharger devices at ~$100 and up being required in addition to the cells themselves

-a hazardous materials uplift for FedEx shipment ranging from $25-$45 depending on destination, on top of normal shipping rates

All of that tells me they're "not ready for prime time" though the current capacity vs weight looks very promising.

I will wait and watch, hoping the technology matures into something safer and less costly as time goes on. Likely it will, particularly the cheaper part, though it appears some safety issues have to be addressed meaningfully.

Thanks for the mention. It is interesting.

Lowell K9LDW

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