There are several variants of the LiFePO chemistry, the A123 being the most obvious example. They all suffer from rather lower terminal voltage than the normal LiPo ones, and all the ones I've seen have metal casings, so the do certainly have a lower energy density/weight ratio. That said, they're all pretty much bomb-proof as far as 'uncontrolled battery excursions' go, ie don't go bang if you do something silly to them.

However, they tend to be quite expensive, which seems to be the main reason that they're not used as much in RC planes. The weight isn't as much of an issue as you might think, as this type of battery tends to be used in quite large aircraft that can handle it easily.



Most of the newer LiPo chemistry variants can be charged at considerably more than 1C now, some I've tried claim up to 5C, although 3C is more likely correct if you want decent cell life. The discharge rate is truly frightening, I have seen up to 35C continuously and 70C in bursts for some of the newest cells, which for example on a 5Ah battery could be over 350A You can easily start a car with a battery you can put in your pocket.

They seem to have remarkably low internal resistance, so they don't even get warm at the rated discharge level. This could work against you, as if the things really did have a 10x current level of energy storage, you could get almost all of it out in a few seconds. They already have the energy density to potentially take your hand off, so...

pca

If anyone is interested in RC-class LiPo packs, the best prices I've found are at hobbyking.com for the Turnigy stuff.

I just picked up a classic Tamiya Porsche 959 to rebuild as a shelf queen late last year and in late November I grabbed a Jammin SCRT-10 (1/10 Short Course) to modify and run. This year I plan to convert a 1970's metal Tonka Bronco into RC.

They've gone through 5 hot summers in a non-AC veranda which turns into a greenhouse, and 5 quite cold winters where it definitely must have gone below 0°C.
I guess I can dispose them. Am I correct in assuming that they should not explode/fire up if broken or short-circuited, when without charge?

When totally discharged (ie, to near zero) they should be fine (should be able to go to standard battery disposal). Got any meaty resistors around?

aka. low-wattage incandescent bulbs?

Even if they're completely flat, don't try to break them open or short them :P

Ok, I'll eventually dispose them. But no, no resistors left around, sorry.


Plenty of those around, actually. How low?


Ok I'll actually make sure they're well protected, if there's still some chance of fire or explosion. The worst thing is to keep them there and forget they even exist.