Amp-hours or joules, you still need to know the voltage of your battery. It seems the strangest criticism being made against me: "Aha! If you're using amp-hours, you must also know the voltage!", as if this is an otherwise irrelevant detail. The exact same people pinging me would have an equally apopepltic fit if I said "just hook up any old battery, voltage is unimportant, as long as you've got a lot of joules!".