LiPo battery question

I fly electric powered planes with Lipos and have had great results. However, I wouldn't use these batteries for the receivers in my glow planes unless I had an extraordinary need for either weight reduction or long, long duration.

The lipos do not have a well documented history for length of service or reliability. They have special charging requirements and can be destroyed through overcharging or discharging at too high of a rate. Failure mode can include a fierce and difficult to extinguish metal fire (remember NASCAR driver Robby Gordon's car bursting into flames while he was leading at Watkins Glen in

2001? - Lipo battery failure in his TV telemetry box). The battery manufacturers recommend charging in a fireproof box (not in a valuable aircraft). They need a voltage regulator circuit for use as receiver power (available from FMA Direct) - another potential point of failure.

NiCads can be used, abused, fast charged at the field in less than 20 minutes and still provide years of service. If you need to save some weight or increase electron supply without gaining weight, then go to NiMh cells and take extra care with charging and monitoring, because they are less robust than NiCads and will not last as long.

Lithium Polymer batteries have opened up new possibilities for electric powered flight. Small electric planes with Lipos and brushless motors can now easily outperform glow planes on a power/weight basis. Planes that will hardly get off the ground and fly for two minutes on NiCads can exhibit sparkling performance and duration on lipolys. That said, I beleive that the extra cost and special care and feeding requirements, along with questionable lifetime, make them an inferior choice for receiver power on glow powered or sailplanes.

Thanks Mike for your wonderful information. The idea was to use it for a 3D model span 1570mm powered by an 50 OS SX that weights less than 1420gr. I'm using 5 Nicads 1000mAh. Weight reduction is always great but after reading your message I'll think I'll stick to my old Nicads as I don't trust to much NiMh. Less robust and more fragile.

Thanks again,

Jan De Bruyne Belgium - Europe

"mike tully" schreef in bericht news: snipped-for-privacy@mb-m07.aol.com...

Or check out the SBEC at

Check out the flight packs at FMA.

Bobby

-- blfinche - Fayette Flyer

_________________

Bobby Fincher snipped-for-privacy@bellsouth.net

----------------------------------------------------------------------------------- Posted from the RCGroups.com Discussion Forums. Visit us at

Go to the SR Batteries Web Site

and see what Larry says about Lipo's and NiMh batteries.

Sure he makes his living selling nicads but his arguments make sense to me.

Regards

Tom Watson Sydney Australia

A story can be told in many ways. In some cases the fact that your are comparing apples and oranges can be hidden by careful wording.

Yes, i think SR has wonderful products.

I get the impression that Larry doesn't want to sell anything that cannot stand up to hundreds of flights and last for years. Yet the average model lifespan is probably 30-40 flights or two years.

You have to take some of Larry's claims with a grain of salt some times.

"All SR cells are screened and matched Aerospace Grade cells. These are not your usual consumer type inexpensive cells. "

SR uses the same high quality Sanyo cells that other suppliers use. They just have a little more robustly constructed pack.

"Only SR puts every pack through five days of electronic testing to make sure every pack is perfect. These tests include a test of capacity, charge retention, and a vibration test for mechanical integrity."

The teardown inspection I have made on cells in S&R packs indicates that the cells are essentially unformed as shipped from the Sanyo factory. They need the same "slow charge conditioning" that any other "new" pack should get. This does not mean that the packs are not top quality, but the quality of the cells is what comes out of the Sanyo production. There is not much you can do to a cell after it is closed other than screen out bad ones by a simple voltage test which most assemblers do as a matter of course when they assemble the packs.

-- Red S. Red's R/C Battery Clinic

us out for "revolting" information.

and 99.7% of all statistics are made up on the spot too.

I'm not sure WHERE you came up with 30 to 40 flights or 2 years, My first plane is still going strong after several people used it to solo on from 1997 to 2003, and I would be hard pressed to even guess at the total number of flights.

One plane that I did count flights on logged 250+ flights (average 8 minutes each) over a period of 11 months.

I have a couple of electrics here that each have over 40 flights each, and are less than 6 months old.

bob

Bob,

Not everyone has your masterful skills. I hope to god that someday I can be half as talented as you. Until then I can only dream...