The Sony VTC series of batteries (VTC3, VTC4, VTC5) are all 30 amp continuous discharge rated batteries. They differ basically in their mAh capacity. There's been a shortage of the VTC5 batteries lately, in part because the facility previously making them in Japan had to be shut down because of the nuclear accident last year, and also because of their extreme popularity. A new facility in the Philipines is reportedly up to speed, but I imagine these batteries will continue to be hard to find in stock.
There have been some recent batteries on the market from previously unheard of manufacturers that claim to be 30 - 40 amp batteries. But they haven't been tested by independent sources to see if the claims are accurate, and many manufacturers/vendors publish the maximum "pulse" discharge rating instead of the more reliable "continuous" discharge rating. Pulse or burst ratings are always higher than continuous and generally not considered to be reliable.
The Sony VTC4 30 amp (2100 mah) can often be found in stock with a lower mAh rating than the VTC5's (2600 mah). These cells are often re-wrapped by other vendors such as the purple Efest 2100 mah, Xtar 2100 mah, and Orbtonic 2100 mah. The purple Efest 2500 mah advertised as "35" amps is actually a re-wrapped LG cell which is only 20 amps continuous.
Purple Efest Batteries Not As Advertised
Do you really need a 30 amp battery? Because there are some excellent 20 amp batteries available that can generally be found in stock. A 20 amp battery can safely fire a 0.4 ohm subohm coil. Samsung, LG, and Orbtonics offer these.
Battery Basics for Mods <-- list of high drain batteries with their specifications
I recommend purchasing from reputable battery vendors such as RTD Vapor, Orbtonics, or Illumination Supply. I'd shy away from purchasing batteries from Amazon or Ebay due to the frequency of counterfeit batteries purchased there.
Deeper Understanding of Mod Batteries
