The Remarkable Lithium Polymer Batteries, by Roger Corum, WD6CNV 

 

All of my RC airplanes are flown by electric power.  I have changed most of the motors to 3 phase brushless motors and they are powered by Lithium Poly cells.  I have read where some QRP ops are beginning to use Lipoly cells.  They are great for this purpose because for their weight, they are amazing! 

 

This is a 3 cell pack that weighs 2 3/8 oz and has 900 MAH capacity.

 

 

 

 

The down side is they are potentially bombs at the worst and a fire hazard at the least.  Charging them requires a special charger and that can't be compromised.   The charge for Lipos has to stop, no trickle charge.  I have been chided for charging mine in the house.  Many guys have built brick bunkers for the battery to be in while it's charged.  The warnings on the pack is right on.

 

When I order packs from the web, you must verify that you have read a warning page and you are the responsible one for their proper care and use.

 

I have seen video of a RC airplane crashing and the Lipo pack heating up until the plane burst into flame.

 

 

 

 

 

And, never short them.  The things just die after one spark, no matter how fast the short was. 

 

I suppose another caution for carrying Lipos into the field is any chance of them being bent or pierced has to be eliminated.  This is when they will begin to self destruct.  If you have seen the cells, they are wrapped in an aluminum foil wrapper about like the popcorn package for camping.  This allows the insides to heat and swell and remain inside the wrapper.  If the foil is pierced, the reaction begins to leak.  This is nasty stuff.

 

 

 

 

If any cell is seen to puff, the pack is best placed into a bucket of salt water.  This allows the cells to discharge slowly to a 0 charge level.  Then they need to be taken to a good recycle station. 

 

These Lipo cells are in almost all cell phones now.  They are the miracle that has allowed them to become so small and yet run for days on a charge.  Most people don't understand that the new chargers have been changed from the old chargers used for NiCads or NIMH cells.  If Lipo cells are purchased, a suitable Lipo charger needs to be purchased at the same time. 

 

Unlike I used to do in the Sierra on QRP packing trips with a small solar panel where I simply connected the little panel to a Gel Cell and let the charge go,  the charge for Lipos has to stop, no trickle charge.

 

(What I would have given for a white LED back then!!)

 

A 2 cell pack is rated at 7.4 volts.  A 3 cell pack is 11.1 volts.  This may be a drawback for someone who wants to have 12 volts.  For those who are willing to operate on a little less power for the weight, the Lipo may be just what you are looking for.

 

 

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