don't buy the ego-T. Not because of exploding batteries, but because it's a crappy system.
First, on the topic of Lipo bags. I never used one and I've been vaping nearly 3 years. However, with the growing demand for PVs, I can only believe that added stress has been added to the supply chain. After reading the accounts of battery issues, I spent the few dollars it cost for a charging bag and like the added security.
As to the Ego style batteries, Sailor is probably right. The components are pretty much the same and all made in China. The question of who assembles those parts might be an issue. I do know that, internally, the composition is different. Some have minimum components- a small wire soldered between the battery and the end cap, a couple wires running from the other end of the battery to the circuit board and finally the wire that runs from the other end of the circuit board to the center post of the adapter. Break any of those connections and the battery will stop working, best case. Worst case, perhaps a meltdown such as this.
I've taken apart different Ego batteries, some have the bare essentials, some have cushioning to absorb shock, thus attempting to prevent accidental failure caused by dropping the battery. As far as using a multi-meter on these batteries, I understand that you need to be careful not to short them out.
My experience has been to stick to the kits where the battery is separate from the unit itself. The batteries last a long time, are relatively inexpensive and the points of failure are reduced. I took the chance on a VV simply because I liked the idea of tailoring the voltage to the atty and the liquid, but realize it adds circuitry not required by purer designs. I bought mine from TW. I've also managed to drop it a few times, once from a three foot table onto a solid wood floor. It kept ticking, although I had concerns about potential damage. I've taken apart and re-soldered Egos that were dropped on carpet and a wire got detached.
I like the size of the Ego and the style for that matter. I just think the design could have been more fault tolerant. BTW and before I close, the TW Ego battery I took apart after it failed was put together pretty nicely. If I were looking for an Ego, I'd look for one from them or someone rlse with a great reputation. That being said, let's face it, batteries fail at some point and I'd prefer one that's easily tested for condition to avoid it failing unexpectedly.