Rechargable batteries..how do i figure this stuff out?

Question

hey! Thanks for clicking in..i'm in a pickle. This is like super more advanced than the rest of my homework and I just can't figure out where to start with formulas. I know P=IV ...P=E/T..can you help?:

Rechargeable batteries are rated in mAh (milli-amp hours). The mAh is a unit of charge: one milli-amp hour is the total charge passing a point in a circuit if one milli-ampere of current flows for 1 hour. Consider nickel-metal-hydride (NiMH) AA batteries rated at 1800 mAh. (The emf of an AA battery is 1.5 volts.)

(a) How much energy can be supplied if 5 batteries are connected in series? (Express the answer in joules, J.)

(b) What is the average power if the batteries last 4 hours before they need recharging?

Answer 1

1800 mA-hr = 1.8 A-hr

1.8 A-hr x 1.5v x 5 = 13.5 w-hr

13.5 w-hr x 3600sec/hr = 48600 w-sec, which is 48600 joules (a)

(b) 48600 joules / 4 hours x 1hr/3600sec = 54 J/sec = 54 watts.

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