[smuzz]

Frank - your 6S battery (roughly 24 volts, as you say) doesn't seem to be high enough voltage to drive enough of a current through the bulb to make it glow. The low current that you are putting through it is enough for some heat loss, but that's it. I presume it's a standard incandescent light-bulb? I don't know what Wattmeter you're using, but it's possible that the current is lower than it's lowest detectable reading which is why it sees the voltage but reports no current.

Your first calculation of 24 Volts * 2.5 Amps = 60 W is fine, but you're not putting 2.5 Amps through it and so the power consumption isn't 60 Watts. 60 Watts is what the bulb is capable of, but it won't necessary consume that much power - only up to 60 Watts. It's probable that the current you're putting through it is only a few hundred milliamps, which means it will take quite some time to discharge.

I presume you're wanting to discharge a battery in order to dispose of it in salt water? If so, discharge it in one of your planes mate, it will only take 6 or 7 minutes