I appologize for not reading all 14 pages so far. To the OP, glad you are ok and no damage was done to your home.
If anything is to be learned from this incident, it is to RESPECT the power that is in these batteries.
For the most part they are relatively safe, but accidents can happen and equipment can fail making them dangerous objects. Ego batteries are lithium ion chemistry batteries - a volatile (flamable) chemistry which can vent hot gas and flames. If they are not able to vent these gases effectively they can explode. This is the same chemistry batteries which are in laptop computers and cell phones, so we don't hear of these exploding.
Practice safe battery habits:
- Charge batteries on a fire-safe surface. I charge my batteries on my stove top. Another option would be to use a glass or metal baking dish/pan.
- Charging bags are controversial. Some say that they will contain a burning battery. Others say that they trap the heat of a charger/battery in an unventilated bag resulting in creating the potential for a problem that wouldn't ordinarily exist. Use your best judgement.
- Never charge your batteries without some attention or being unable to intervene should an emergency happen. You can't call the fire department or use a fire extinguisher if you aren't inside the house to witness the event.
- Not a good idea to charge a battery overnight while you sleep. Take the battery off of the charger soon after a full charge. Most chargers stop charging when the battery is fully charged, but many continue a trickle charge to keep the charge at full. Lithium batteries do not like this and it can cause a decrease in overall battery longivity.
- For eGo chargers, use only USB/wall adaptors like most cell phones use. Do not use computer USB ports or car USB ports.
For users of replaceable rechargeable batteries in mods, I recommend using only safe chemistry batteries instead of so-called protected ICR batteries. Batteries such as IMR and the newer hybrid batteries are safer than the "old school" ICR batteries with protected circuits built in.
If your mods have on/off features, use that feature when putting the mods in purses or pockets. I had a protected battery explode in a mechanical mod in a pants pocket when the fire button got stuck in the "on" position (luckily I wasn't wearing those pants when this happened).
If your mod does not have the on/off feature or a locking fire button, remove the delivery device on top to break the electrical connection with the battery.
Do not carry spare batteries in pockets or purses without being in a safe plastic case. Plastic Battery Cases Contact with metalic objects such as coins or keys can cause a battery to vent. Below is a pic of an IMR battery which came in contact with something metalic in the pocket of a book bag.
Battery Basics for Mods: IMR or Protected ICR?
Mechanical Mod Proper Usage Guide