If you've followed the various columns in MA and other places, LiPo's don't need an excuse to go bad during charging.  It doesn't happen often, but when it does it can be pretty catastrophic.  The one MA columnist a couple of months ago had a seemingly perfectly performing LiPo go up in smoke during a normal charge.  There are good sound reasons for the charging safety advice- never charge in the plane or indoors, put the battery in a fireproof container, and don't leave it unattended while charging, if the battery is ever in a crash get it out of the plane as soon as possible and keep it in the fireproof container until you're satisfied it hasn't been damaged.

Hi Alan,
Hi Phil,
I was perplexed to see the approach taken in that article. For one thing, the idea of accepting the inevitability of catastrophically destroying batteries on a semi-regular basis blows my mind. The writer is probably still abusing his batteries without solving the original problem. The idea of building a rig to catch the beginning of disaster, and terminate charge, is not entirely bad. I understand that Motorola build a pressure sensor into the LiIon cell phone packs for just the same reason. Secondly, I don't buy the statement that LiPos don't need an excuse to go awry. No Sir! Batteries vent with flame for one of several reasons ( which all boil down to imbalanced overcharging).

1) Mechanical damage: even the vast majority of cell phone flame-outs happens immediately or shortly after a good hard drop to a concrete-like surface. (about 75 exploding cell phones per year in the USA) On the other hand I have a buddy who has put 70+ additional flights on a 5S/5.3 A-H pack that jettisoned from a Pattern plane at 200' and landed in soft grass! Go figure ...
2) If one cell in the pack overcharges sufficiently it will be damaged, puff, and maybe vent. This often happens because the pack becomes imbalanced and while the entire 4S pack may have reached the correct 16.8 V charge termination voltage, some cells will be lower and others too high. It doesn't take much. A balancing charger like the FMA Balance-Pro, CellPro, or Thunder Power balancing series is the safeguard here. Even well treated batteries can become imbalanced, though it takes many many cycles for this to happen. The industry is catching up, here. By the way, balance is less important after discharge: it is vitally important at full charge.
3) Over discharge is often the cause of imbalance. LiPos should never be run without a properly set ESC low-voltage cutoff of 3.0 V per cell or maybe slightly higher. I'd bet money on this one as the most common cause of problems: running down till the power droops was acceptable with nickel-based cells but not lithium. For less weight critical missions, a battery monitor that looks at each individual cell and shuts down the motor if any one of them droops below 3.0V is the best solution. For our weight-critical mission, just don't drain them below 80% charge used ... ever, and use a balancing charger often if not all the time.
4) Over-currenting and overheating LiPos wounds them and reduces capacity. Of course, the individual cells will not all be identically abused (think of the ones in the middle of the pack) and the imbalance will later cause problems at charging time.
We already take this much care in filtering the fuel we use in our wet-powered Stunters. It's just a different skill set.
Sorry if I come on strong.

later Friends,
Dean P.

Yes Mike,
And because you paid attention each time something out of the ordinary happened there were never any flames. Let's face it you were watching/listening to the Astro 109 beep out its error codes. That alone prevented disaster.
There is an FMA charge protection module which can be put in between any "normal" LiPo charger and the battery. It also needs a balance connector, but while the FMA CPM does not balance packs, it will disconnect the pack from the charger (and beep angrily) if any one cell starts to become overcharged. Neat item, and it's worthwhile to wire up an adapter to your battery. Maybe FMA can even provide one.
later,
Dean

Mark,
   If you plan to store your Li-Po's for a long period of time store them around 3.8 volts per cell and throw them in the refrigerator (35-55 deg). If you are flying them every week or every other week you can store them at any voltage (above 3 volts per cell) and you can store them at any temperature (above freezing). You won't see any degradation if they are not stored in ideal conditions on a week to week basis, only long term. If you do store them in the refrigerator let them warm up to room temperature before charging/discharging.

   As for new (used) Li-Po's I would check the total voltage of the packs. If they are in check you can charge the packs while keeping you eye on them. If you have a balancer you may want to balance the packs before charging or charge while the balancer is attached. If the packs are damaged it doesn't matter what you do to try to save them. The damage is done. The only thing you may prevent is a ballooning or venting situation.