Buying Guide – How to Shop for CPAP, BiPAP, and APAP Batteries and Converters
Positive air pressure therapy, or PAP therapy, is used to treat obstructive sleep apnea (OSA) or central sleep apnea (CSA), conditions that cause temporary loss of breath during sleep due to airflow restrictions in breathing passages. PAP therapy comes in several forms; the most common types are continuous positive air pressure (CPAP), bi-level positive air pressure (BiPAP), and automatic positive air pressure (APAP).
All PAP therapy types feature an airflow generator (known as the PAP machine) that draws in outside air using an electric fan, humidifies and pressurizes the air, and then delivers it to sleepers through a connective hose and a nasal or full face mask.
Power source is crucial for this type of therapy since most devices require some sort of electric current. Most are primarily designed for AC power, but can also run on DC batteries or inverters under certain circumstances, such as power outages. This guide will discuss the important factors to consider when shopping for a battery or inverter used with CPAP, BiPAP, and/or APAP machines.
Power Requirements and Options for PAP Machines
CPAP, BiPAP, and APAP machines need power to operate. Most nightly users rely on AC voltage, and operate their machine using power cords plugged into wall outlets. AC outlets in North America produce 110 volts, but the voltage output number varies in other parts of the world (see next section).
However, AC voltage may not be readily available — particularly for PAP users who are traveling. A recent survey found that more than three-quarters of people that rely on PAP therapy bring their machine when they are on the road. DC battery voltage is a potential alternative for PAP machines in these instances. Users can operate their machine using DC power in one or more of the following ways:
- An inverter, which changes DC voltage into AC voltage.
- A DC power cord, which connects to 12-volt outlets; most of these cords are designed to connect with cigarette lighter outlets.
It’s important to note that an inverter is not needed for machines that are compatible with DC power cords. However, virtually all PAP machines sold today can be operated with inverters. To determine whether an inverter is required, check the machine specifications for verbiage related to a ‘DC outlet.’ If specifications are not available, check the machine itself; the outlet is normally located on the back or side.
It’s worth noting that very few PAP users rely on battery power. According to survey results, roughly 10% of PAP users have ever utilized battery power to operate their machine; the vast majority of respondents who have used a battery did so for travel-related purposes.
When determining battery selection, it’s important to consider the PAP machine’s pressure settings. The airflow delivery of PAP machines is measured in centimeters of water, or cmH20. A standard PAP machine will deliver an airflow range of 4 cmH20 to 20 cmH20. The higher the setting, the more power that will be needed to operate the machine. CPAP machines deliver airflow at a fixed (or continuous) pressure rate throughout the night, while BiPAP and APAP machines toggle between two or more pressure settings based on the sleeper’s breathing patterns. Most PAP users receive at least 10 cmH20 of airflow at any given time.
Due to the power requirements for higher pressure settings, robust batteries are often needed to power a PAP machine throughout the night. These machines require a fair amount of power, Power needs may be magnified by using an inverter and/or a heated humidifier, which both tend to use up a large amount of battery life. The following battery options tend to work best when powering PAP machines:
Deep-cycle marine battery: Deep-cycle batteries expend a small amount of energy over a longer period of time. While performance varies by model, most deep-cycle marine batteries will power a PAP machine for at least two consecutive nights (depending on the pressure setting) before recharging is needed. In order to use a deep-cycle marine battery with a PAP machine, a DC adapter cable is needed; this attachment connects to the cigarette lighter attachment of the DC cable, and features alligator clips (like those found on jumper cables) that connect directly to the battery.
It’s important to note the difference between deep-cycle marine batteries and starting marine batteries, which expend larger amounts of energy over shorter periods of time. Additionally, dual-purpose marine batteries are designed to serve both functions; however, these batteries typically do not match deep-cycle or starting batteries in terms of duration or energy output, respectively. Because PAP therapy requires several hours of power, deep-cycle marine batteries are considered superior to starting and dual-purpose marine batteries for powering PAP machines.
Battery packs: A PAP machine can also be connected to lithium ion battery packs using the DC cable adapter described above. Battery packs are lighter and more portable than deep-cycle marine batteries, but most need to be recharged every one to two nights (depending on the pressure settings). Also, please note that most battery packs sold today are only compatible with a limited selection of PAP machines — or only one model, in some cases.
Backup battery: A small number of PAP machines sold today come with built-in batteries that will power the machine when other sources are unavailable. If a PAP machine does not come with an integrated battery, then a battery pack may serve this function.
The table below illustrates some of the main differences between these three battery options: