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What Does 100Ah Mean on a Battery?

Power - by Bryan Veldboom - updated on 12/22/2021

Large RV parked in a camp ground

If you're new to the world of RVs, you've probably heard someone refer to 100Ah batteries at some point, but what is a 100Ah battery? Today we'll be taking an in-depth look at how 100Ah batteries work and why they're popular batteries with RV owners. We will also share how 100Ah batteries work within a solar charging system.

What is an Amp Hour?

An amp hour, also known as an ampere hour (Ah), tells you the amount of current a battery can supply for exactly one hour. This is its capacity. In order to make sense of that though, we need to define a few key electrical terms first.

  • Amps - (short for "amperes") a unit used to measure electrical current. Current is the speed at which electrons flow through an electrical conductor.
  • Volts - a unit used to measure voltage. Voltage is the difference in electrical potential, or the number of electrons, between any two points in a closed electrical circuit.
  • Watts - a unit that measures the power that is generated from amps flowing through a volt's electromotive force. Watts are calculated by multiplying the number of amps by the number of volts.

What Does 100Ah Mean?

Ah rating of a battery indicates the battery capacity or the amount of ampere hours it can handle. A 100Ah battery means that the battery can supply a load of 100 amperes in one hour, or 50 amperes for two hours or 10 amperes for 10 hours.

How is the Flow of Electricity Similar to the Flow of Water?

An easier way to understand the terms above is to compare electricity to water flowing through a hose. In this analogy, amps represent the speed of water flowing through the hose. Voltage is the hose's water pressure and watts are the amount of water coming through the hose. Amp hours would tell you how much water will flow through the hose over the span of an hour.

Why are 100Ah Batteries So Popular for RVs?

The 100Ah 12 volt sealed lead acid (SLA) battery size is widely used because it is the largest capacity 12V SLA battery that can be easily moved by one person. It's also reasonably priced, takes up relatively little space and packs enough energy to run lights, charge cell phones, and run small accessories.

Why is It Necessary for the Appliances to Match the Voltage Source?

It is important to make sure that your battery's voltage matches that of your appliances. Batteries always have a fixed average voltage. Likewise, appliances are designed to operate at a specific voltage. For that reason, it's important that the voltage of your battery matches the voltage requirements of any appliances it will be powering. RVs typically use 12V batteries, but 6V, 12V, 24V and 48V systems exist.

Most RV appliances and lighting require 12 volts of electricity. This gives you two options. You can either go with a 12V battery or use two 6V batteries in series. Keep in mind though that if one of those two batteries goes bad, you won't be able to use the remaining 6V battery to power your appliances. To cater to high voltage systems, 12V batteries can be used, with caution, in series.

How Long Will a 100Ah Battery Last?

A 100Ah battery has 100 amps of capacity at its disposal. How long it can run depends on the electrical requirements of the applications you're powering and how many of them there are. A 100Ah hour battery will supply 1 amp of current for 100 hours, 2 amps for 50 hours or 100 amps for one hour.

So, let's break that down into more concrete terms. A laptop uses about 5 amps of power. If you plan on using it for 8 hours a day, you will require 40Ah of capacity for a single day. Using a 100Ah battery, you could power your laptop for 2.5 days before the battery needs to be recharged.

How Many Batteries Do I Need to Power Multiple Appliances?

Chances are you're probably going to be powering multiple applications in your RV simultaneously, which may exceed what a 100Ah battery can provide. Calculating the total power (in amp hours) that your appliances require per day will help you determine the size and number of batteries you need to run your applications. Here is how to do that:

  • Start by making a list of all of the appliances on your RV.
  • Determine how many amps each application requires in order to run.
  • Multiply the number of amps each application requires by the number of hours you plan on using that appliance per day. This will give you the total power consumption of that appliance for the day.
  • For example, a laptop uses 5 amps of power. If you plan on using it 3 hours a day, your total daily power consumption for the laptop would be 15 amps of power.
  • When the list is complete, add up the daily power consumption of each appliance to tabulate your total power consumption (in amp hours) per day.
  • Once you have your total power consumption for the day, select a battery (or batteries) with a high enough amp hour rating to cover your electrical needs.
  • Since lead acid batteries can only be discharged to about 50% of their total capacity, you'll need to divide the battery's listed number of amp hours by two. This will give you the actual usable capacity for the battery. For example, a 100Ah battery will only provide you with 50Ah of usable capacity.
  • Lithium iron Phosphate batteries can discharge much lower than lead acid batteries so you don't need to cut their amp hour total. See the manufacturer's recommendations in order to determine how low they can be discharged.

How Many Watt Hours are In an Amp Hour?

If you need to convert amp hours to watt hours, you can do this by multiplying the battery's amp hours by the battery's voltage. Using that equation, the number of watts a 12 volt 100Ah battery can provide in an hour, would be calculated like this: 100 amp hours x 12V = 1200 watts hours or 1200 watts for one hour.

What is the Difference Between AC and DC Power?

Near the bottom of the solar sizing worksheet there is a section that states "AC amps are converted to DC by multiplying by 10." What does that mean exactly? Your RV battery gives off Direct Current (DC), which behaves differently from the Alternating Current (AC) that's used in your home's electrical system. When calculating your power needs, it's important to take this into account, which is why the worksheet suggests converting AC amps to DC amps by multiplying them by 10. While this is not an exact conversion, it is useful for the estimation of power needs.

When powering appliances directly from your RV battery, you will need a power inverter, which converts 12V DC power to 120V AC power. If you try charging a cell phone or powering an AC appliance using DC power, you'll severely damage it. Batteries Plus offers a selection of power inverters online.

What are the Different Types of RV Batteries?

It's important to note that RVs typically have two separate batteries onboard, a starting (SLI) battery and a deep cycle battery. Starting batteries are manufactured to provide short, intense bursts of energy. This makes them great for starting engines, but poorly equipped to function as a house battery. This is what a deep cycle battery is for. Deep cycle batteries are designed to provide smaller amounts of power for a longer period of time. When we talk about 100Ah batteries here, we're talking about deep cycle batteries used to power things such as lights, clocks and other appliances. Read more about RV battery options.

What are the Different Types of Deep Cycle Batteries?

You'll want to pay attention to the chemistry of your deep cycle battery as it will impact how effective the battery performs. There are two types of 100Ah deep cycle batteries available from Batteries Plus: Lead acid and Lithium Iron phosphate (LiFePO4). The key differences between the two are performance and price. LiFePO4 batteries will cost more upfront, but run longer, recharge faster and have much longer lifespans. For more information read The Complete Guide To Lithium Vs Lead Acid Batteries   from Power Sonic.

Using a 100Ah Battery in a Solar Charging System

Many RV owners charge their batteries using solar charging systems. A solar power system uses a number of components working in tandem to collect, store and deliver power to your RV battery. The system's solar panels are responsible for collecting sunlight and converting it into the DC current used to charge your RV's battery.

What Size Solar Panel to Charge 100Ah Battery?

Solar panels are rated by the amount of DC power they produce under ideal sunlight conditions, which is often measured in watts. You can calculate a solar panel's total solar output by multiplying its wattage rating by the number of hours of direct sunlight it receives per day. So, using that equation, a 100 watt solar panel receiving 5 hours of sunlight per day will have a total output of 500 watt hours (Wh).

How Long Does It Take to Charge a 100Ah Battery Using Solar Panels?

The charging time will depend on the type of battery, its state of charge, and the power output of your solar panel(s). As an example though, let's say you have a 12V 100Ah lead acid battery that has been discharged to 50Ah. Using a 100W solar panel in optimal sunlight would have an output of roughly 8.33 amps. Use this equation to get a rough estimate of how long it would take to recharge: 50Ah/8.33 amps = 6 hours to recharge. Realistically, it would probably be somewhere between 6 and 7 hours since you never get the full solar charge for that length of time. Of course, you can speed this up by using multiple solar panels.

Get Your Batteries and Other RV Essentials at Batteries Plus

Need a battery replacement? Shop our selection of starting, deep cycle and dual purpose RV batteries online, including 100Ah and 125Ah lithium iron phosphate batteries from Power Sonic. We also offer a number of solar energy solutions, including power stations from Goal Zero. Still have questions? No problem, call or stop by one of our 700+ locations. Our in-store experts will be happy to help you find the right equipment and heavy-duty products to match your RV's needs.

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