What are Amp-Hours in relation to Solar Power Batteries?

Question

1.Say you have 12 volt 60 amp-hour battery, and you have an appliance that uses 1000 watts to run it. How do you calculate how long you can run the appliance with this battery?

2. If you connect two 60 amp-hour batteries do you have 120 amp-hours?

I'm new to solar energy and want to know what the technical terms mean.

Answer 1

The first answer is good.

Here's an explanation of Amp-Hour.  Amp-Hour is a rating of energy availability.  Your battery is rated at 12V and 60 amp-hour so, theoretically, if you have a load that is drawing 60 amps your battery will maintain 12V for one hour.  The amp-hour rating is not linear though.  If you put a load of 120 amps on this same battery it would last about 20 minutes, depending on the type of battery.  Conversely, if you only had a 30 amp draw on the battery it last about 3 hours.

With your 1000 watt analogy, at 12 Volts, you would have a draw of 83 amps so your battery would only only last about 30 minutes.

Answer 2

You cannot convert watts to amps, since watts are power and amps are coulombs per second (like converting apples to miles). If you have at least least two of the following three: amps, volts and watts then the missing one can be calculated. Since watts are amps multiplied by volts, there is a simple relationship between them.

Converting Watts to Amps

The conversion of Watts to Amps is governed by the equation Amps = Watts/Volts

For example 12 watts/12 volts = 1 amp

Converting Amps to Watts

The conversion of Amps to Watts is governed by the equation Watts = Amps x Volts

For example 1 amp * 110 volts = 110 watts

Converting Watts to Volts

The conversion of Watts to Volts is governed by the equation Volts = Watts/Amps

For example 100 watts/10 amps = 10 volts

Converting Volts to Watts

The conversion of Volts to Watts is governed by the equation Watts = Amps x Volts

For example 1.5 amps * 12 volts = 18 watts

Converting Volts to Amps at fixed wattage

The conversion of Volts to Amps is governed by the equations Amps = Watts/Volts

For example 120 watts/110 volts = 1.09 amps

Converting Amps to Volts at fixed wattage

The conversion of Amps to Volts is governed by the equation Volts = Watts/Amps

For Example, 48 watts / 12 Amps = 4 Volts

Amps are how many electrons flow past a certain point per second. Volts is a measure of how much force that each electron is under. Think of water in a hose. A gallon a minute (think amps) just dribbles out if it is under low pressure (think voltage). But if you restrict the end of the hose, letting the pressure build up, the water can have more power (like watts), even though it is still only one gallon a minute. In fact the power can grow enormous as the pressure builds, to the point that a water knife can cut a sheet of glass. In the same manner as the voltage is increased a small amount of current can turn into a lot of watts.



In theory 2 60 amp hour batts would give 120 amp hours but in practise it is not the case. The wiring has resistance, and you would probably never get the batts to accept a complete charge etc.