Amp Hours (Ah) or Kilowatt Hours(kWh)?

Amp Hours or Kilowatt Hours Measuring Battery Capacity and Electrical energy

In days gone by, it was and has been common place to measure the load or size of a 12 volt RV Solar system, or better said, the battery capacity of an RV electrical solar battery in it’s Amp Hours.

Per the Inch Calculators website

“Amp-hours, often expressed as Ah or A·h, are a measure of electrical charge. Amp-hours are often used to measure the charge capacity of a battery, for example. One Ah is the amount of electrical charge transferred by one amp of current in one hour of time.” *

This has been the standard when trying to decide the capacity of a solar system battery bank.

21,600 Kilowatt Hours of battery capacity at 24 volts

For example, in a larger solar set up, assuming the system is running on 12 volt, you would want to see 600 AH of battery capacity at a minimum. This can be achieved by purchasing 6 -100 amp hour batteries, 3 -200 amp hour batteries, or 2 -300 amp hour batteries. In each of these scenarios, the batteries are wired in parallel (linked together) into the system to provide you with your total amp hours.

This has been the standard for years.

However, over the past 3 years or so, we are seeing significant gains in 24 volt systems and now, 48 volt systems.

There is a significant value in considering a 24 volt system instead of a 12 volt system. Better still, taking the leap to 48 volts is far superior.

There are a number of reasons for choosing a higher voltage. At the top of the list for me has to be the increased efficiency in converting the voltages at the DC current into the needed AC current.

Converting 12 volts to 120 volts to power the A/C side of the RV requires “amplifying” the voltages by 10 times! This creates significant pressure through the wiring as well as heat. It also is hard on the appliances at start up.

24 volts cuts that in 1/2, down to only 5 times conversion and 48 volts down to a mere 2.5 times.

The less intense the conversion, the less heat build up, the less strain on wiring (hence cutting wire sizes in 1/2 or even greater) and the greater overall efficiency.

48 Volt 100 Ah Lithium Battery

This is where we need to begin quantifying our system battery “capacity” into kWh, or Kilowatt hours.

According to the same website above, Kilowatts are defined as follows.

“Kilowatt-hours, expressed as kWh or kW·h, are used to measure electrical energy. One kWh is equal to one kilowatt, or one thousand watts, of power consumed for one hour of time.”

In the future, all of our systems being sold will now be listed by kWh.

Here’s why.

It is our plan to begin phasing out 12 volt installs entirely and moving to 24 volt at a minimum and on medium to larger systems 48 volt systems.

The benefits are almost too many to list.

If we were to list the Ah of a 24 volt battery, it would seem “smaller” by system standards if we listed the Ah of the battery on a 12 volt system to most folks not familiar with the differences.

Here’s an example.

If I were to list a 150 Ah battery being installed for a 24 volt system, it may seem like the system has a small battery. However, it is not as small as it may seem.

This is because a 24 volt battery at 150 Ah is the equivalent of a 300 Ah battery in a 12 volt system.

Similarly, a 100 Ah battery in a 48 volt system is the same battery capacity in the Kilowatt hours available as 400 Ah in a 12 volt system.

Hence my reasoning toward listing the kWh for the system.

A 100 Ah 48 volt battery will contain 4800 available kWh or Kilowatt Hours.

A 400 Ah battery bank at 12 volts will contain the same 4800 kWh or Kilowatt Hours.

The system sold is better represented now listing the available Kilowatt Hours available in the battery bank as opposed to the Amp Hour capacity of the battery bank.

This is why you will notice that systems sold by me here at Rob the RV Guy will now list the capacity in the Kilowatt Hours of the battery bank instead of the Ah of the system.

If you have any questions, please reach out to me through our contact form. I am happy to discuss a potential system for you.

rob out

* Credit to https://www.inchcalculator.com/ah-to-kwh-calculator/