# Watt-hour vs Amp-hour - Battery life

This might sound silly but I am new to electronics and trying to understand the difference between watt-hour vs ampere-hour when it comes to battery life per charge.

So let's consider this scenario.

I have a circuit that runs for 7 days when connected to a 3.7 V (1200 mAh) battery. Here the watt-hour of the battery is (3.7 * 1.2) 4.44 Wh.

Now if I connect a 12 V (1200 mAh) battery which provides (12 * 1.2) 14.4 Wh and use a voltage regulator, will I be able to run the circuit for more than 7 days on a single charge?

EDIT:

The circuit voltage requirement is 3.7 to 4.4 V and consumes 500 mA when active for 10 seconds and then it goes into a deep sleep for 5 minutes. During deep sleep, it only consumes around ~50 uA. My goal here is to get the maximum battery life (more than 60 days) from a single charge.

• SI units named after a person have their symbols capitalised but are lowercase when spelled out. 'W' for watt. 'V' for volt. 'A' for ampere. Capitals matter. SI standard also recommends a space between the number and the units (same as "5 cups" rather than "5cups"). Commented Dec 21, 2020 at 12:50
• Depends on the regulator how much it consumes power. And what is the usable voltage range on battery. Do you have a specific battery types, specific regulator, and specific load in mind? If no, we are just guessing here and the question is not answerable. Commented Dec 21, 2020 at 12:54
• @Transistor Specifically a non-breaking space, though it's not really worth the trouble most of the time. Commented Dec 21, 2020 at 13:03
• If the regulator is a linear regulator then that regulator will simply "burn" (turn into heat) the extra energy from the 12 V battery. With a linear regulator the current consumed stays the same and since the battery capacity remains 1200 mAh, the amount of current * time does not change and the 12 V battery will give roughly the same runtime on a single charge (assuming you're not depleting the 12 V battery down to 3.7 V as that damages the battery!). Commented Dec 21, 2020 at 13:04
• However if the regulator is a switching regulator and it is an efficient enough design then it is possible that the 12 V battery will give you a longer runtime. A switching regulator will not just "burn" the extra voltage but it will convert the voltage down more efficiently resulting in a lower power consumption compared to the linear regulator situation. So with a switched regulator and a battery that has a higher amount of energy, a longer run time is possible. I'm not saying: "You will always get a longer runtime" as the design needs to be correct. Commented Dec 21, 2020 at 13:09