I felt crazy for a second, but you both have it backwards. Running 2 batteries in series means doubling power, (12 v + 12v = 24v power) but same amp/hour as a single 12v. running the same 2 batteries in parallel means 12v of power, but double the amp/hr.

Source: Am an electrician with shit memory, google confirmed it.

[–] areyouevenreal@lemmy.antemeridiem.xyz 1 points 1 year ago

Volts don't measure power. Also nobody specified the load was resistive. Most loads are not resistive. See light bulbs, diodes (inc. LEDs) and even electric motors as an example. If you are talking about resistive loads you need to specify that. For a resistive load doubling the potential difference (volts) causes the current to also double because I = V / R and power to quadruple P = VI. So run time would half since you are spending double the energy at four times the power (power is rate of energy consumption).

I am now disappointed in people who call themselves electricians.