@Topwater Elvis is quite correct that you don't need to know Ohm's law for a regulated device like the Aegis X, but I thought I'd clarify a few things in any case.
In an unregulated mod (also known as a mech mod), the batteries connect directly to the coil, so the amount of power being used is determined by the batteries' voltage and the coil resistance. In a regulated mod, there's a circuit board between the batteries and the coil. The circuit board provides the 'regulation'. Tt determines how much power is used based on your wattage setting.
You say you have 25 A batteries. The 25 A is the batteries' continuous discharge rating (CDR). That means it's the amount of power the battery
can provide with relative safety; it's not the amount of power it's actually providing at any given time. To use an Ohm's law calculator, you'd enter your maximum voltage (the 8.4 v) and coil resistance (0.11 ohm) and leave the amps blank. The calculator would then work out the amps being drawn from the battery (of an unregulated device) under those conditions, which is the 76 amps you saw. As you noticed, that's way over what the batteries can provide safely so it wouldn't be a good setup at all.
However, you're using a regulated mod, not an unregulated one. You won't get to 76 amps - unless you've managed to set your wattage to 641. The rule of thumb for determining the maximum safe wattage for regulated mods (both serial and parallel) is:
Wattage = # of batteries * CDR * 3
In your case, that's
2 * 25 * 3 = 150 watts
So, as long as you stay below 150 watts, you should be OK. It's worth noting that the CDR is for new batteries in good condition, so that upper limit should drop a bit over time. Also, batteries don't tend to work as well (they don't last as long between charges and they get stressed and age faster) as you approach the CDR, so it's best to stay a fair bit below it most of the time - maybe around 120 watts - to get the best performance from your batteries.
