Need help identifying a "tank" type battery (Picture)

[Ryedan]

One thing that is VERY I PORTANT with a twist style variable voltage battery...
When charging, MAKE CERTAIN TO SET THE VOLTAGE TO 4.2 VOLTS!!!
This style battery will not charge properly if the voltage is not set prior to charging. When you charge, these basically backfeed through the voltage regulator, and will not fully charge is the dial is set too low.
If you have a pass through charging port, setting the dial for charging is not needed, as the battery has a seperate charging circuit.
If you screw your charger in place of your tank, this is a MUST DO in order to charge properly. You Will overheat the circuit and could burn it up if you dont.

I've never heard of this before and it makes no sense to me. If you have more information or a link to share that explains it better or confirms it, I would love to see it

A standard 420mah 5volt usb charger is fine. The usb standard is 500mah max for computer usage, so a 420mah charger will charge yoyr batteries just fine, but will take a while. 4 to 6 hours if fully discharged.
You can also get a "tablet" type charger (2.1a) or cell phone charger (1.0a) and you can charge a lot quicker if you have a standard micro usb port for the charging adaptor.

There are a couple of things wrong with the above. If you have a 650 mAh Twist and you charge at 420 mA you'll have it fully charged in no more than 2 1/2 hours. Most of time it takes less than that because the battery is not completely discharged. Mine have never come close to 4-6 hours.

The charger is not going to pull more than 420 mA from the power supply weather it's available or not. Because of that it will not charge any quicker no matter how much current is safely available. OTOH, if the USB power supply is overloaded it can heat up and burn out.

 

[AlAmantea]

In most setups, you are almost correct, as the charging circuit is directly connected and can monitor the voltage through the battery directly. However, with a twist (manual voltage adjustment), you are not connecting directly, you are backfeeding through the voltage regulator (amplifier) circuit in order to charge. Simple ohms law tells us that in order to fully charge, we need to overcome the resistance. If the dial is set too low, we never truly reach a full charge with the battery. Once the battery hits the dial voltage, the charging circuit will assume that it is at full charge, due to the resistance feedback into the charge circuit. Li batteries are not charged like NiCads, and need to be monitored during charging. Hence the reason for different chargers. IE: dial set at 3.8v = when the battery hits 3.8 volts, the regulator will change resistance in order to maintain that voltage. The charger then sees the resistance change, and assumes full charge.
This is the simple reason why so many people are having issues charging their batteries with a vv battery.
If you have a pass through charger circuit, this step is unneeded, as the charging circuit is directly connected to the battery, and bypasses the regulator (as in an itazte vv). I cant remeber right off where i learned of this issue. It came from a factory rep (i believe it was Kangertech, but dont remember for sure). Ever since i started adjusted my vv batteries to 4.2 when charging, i have had zero issues with battery life or overheating. I can charge anywhere, with any 510 charger without a problem.
If you have issues with your vv battery life, just try it. It works (and makes sense if you think about it), but it may take a couple of charges to reset your battery. Drain it down till it shuts off, then charge it. Do it again, and you should be back to normal.

My vv twist is a 1000mah kanger, so theres the 4 hour charge time.