If your CPAP is plugged into an EXP PRO battery and the battery's charger is plugged into the wall, your CPAP is running on the battery the whole night. The charger just keeps the battery topped up. When the power goes out, nothing switches over, because the CPAP was already on battery power, so there is no gap to wake you up.
That setup is called pass-through charging. It turns the battery into a CPAP battery backup that works like a UPS with a 0 ms transfer time. The rest of this page covers how many nights you can expect, what to do about the humidifier, running two machines, recharging during a long outage, and how to set it up once and leave it.
How pass-through charging works
In pass-through, power flows in one direction: wall outlet to charger, charger to battery cells, battery cells to your CPAP. Your CPAP never draws from the wall directly. It draws from the battery, and the charger replaces what it uses.
When the grid drops, the only thing that changes is that the charger stops putting energy back in. The CPAP keeps drawing from the same cells it was drawing from a second earlier. There's no detection step and no switchover.
Why "nothing switches" matters
Many power stations advertise a UPS mode with a switchover time measured in milliseconds. In that design, your device runs on wall power until the unit detects an outage, then it switches to the battery. Most of the time that is fast enough. But it is still a handoff.
With an EXP PRO battery in pass-through, there is no handoff to time. The transfer time is 0 ms because there is nothing to transfer.
You can leave it in pass-through all the time
You don't need to save pass-through for stormy nights or nights when an outage is forecast. Plug the CPAP into the battery, plug the charger into the wall, and leave it that way every night. You can leave it that way all the time.
How many nights you'll get
These are estimates. Your real runtime depends on your pressure setting, your machine, whether the humidifier and heated hose are on, mask leak, the battery's age and the room temperature.
| Humidifier and heated hose off | Estimated nights |
|---|---|
| EXP48PRO APEX (153.6Wh) | About 2–3 nights |
| EXP96PRO APEX (307.2Wh) | About 4–6 nights |
Turning the humidifier and heated hose on cuts runtime sharply. With both on, the EXP96PRO APEX gets roughly 1 night. For a number based on your own machine, pressure and humidifier settings, use the CPAP battery runtime calculator.
During an outage, "nights" start counting from when the grid went down. If the outage starts at 2 a.m. on a fully charged battery, with the humidifier and heated hose off, you finish that night and still have most of your capacity left for the next one.
The humidifier and heated hose during an outage
The humidifier and heated hose are the biggest power draw on most CPAP machines. On the EXP96PRO APEX, running both cuts the estimate from about 4–6 nights to roughly one.
On a normal night in pass-through, that doesn't matter much, since the charger is refilling the battery. Once the power is out and you don't know when it's coming back, it's worth turning them off to stretch what you have. We have a step-by-step guide to turning off the heated hose and humidifier for common machines.
If dry air bothers you with the humidifier off, these may help:
- Why adding water can still help with the humidifier off
- Heat moisture exchangers (HMEs) and why you might consider one
If you're not sure whether running without humidification is right for your therapy, talk with your sleep or equipment provider ahead of time.
One machine or two
If two people in your home use CPAP or BiPAP machines, you have two options.
One EXP96PRO APEX. It has two DC output ports, so one battery can run two CPAP or PAP machines at the same time. Both machines share the same 307.2Wh, so expect fewer nights per machine than the single-machine estimates above.
Two batteries connected together. You can connect two of the same EXP PRO battery to double capacity; call 360-686-7424 and we'll walk you through the setup. Two EXP48PRO APEX batteries together give you about the same capacity as one EXP96PRO APEX.
Recharging during a multi-day outage
If the outage looks like it will last more than a night or two, plan how you'll recharge before the battery runs low.
From your car. Both batteries charge from a vehicle's 12V outlet. The EXP48PRO APEX takes about 4 hours from a car; the EXP96PRO APEX takes about 8. Basic carbon monoxide safety applies: the CDC says never to run a car or truck inside a garage attached to a house, even with the garage door open (CDC: carbon monoxide poisoning basics).
From solar.
| Battery and panel | Charge time |
|---|---|
| EXP48PRO APEX + Summit 60W | Under ~5 hours |
| EXP96PRO APEX + Summit 60W | Under ~9 hours |
| EXP96PRO APEX + Summit 100W | Under ~4.5 hours |
Solar times assume good sun. Clouds, panel angle and short winter days all slow it down.
From the wall, when power returns. AC charging takes about 2.5 hours for the EXP48PRO APEX and about 5 hours for the EXP96PRO APEX. If you're in pass-through, this happens on its own as soon as the power comes back.
Generators
A generator and a battery do different jobs. The generator covers big loads like the fridge or a well pump. The battery sits quietly next to your bed and runs the CPAP all night, so you're not running a generator for one small device or listening to it while you sleep.
Generator safety, paraphrased from the U.S. Consumer Product Safety Commission (CPSC generator safety guide):
- Never use a generator inside a home or garage, even if doors and windows are open.
- Run it outside, at least 20 feet from the house, away from windows, doors and vents, with the exhaust pointed away from the home.
- Install battery-operated or battery-backup carbon monoxide alarms outside sleeping areas and on each floor, and test them monthly.
Utility medical programs and Medicare
Utility programs. Many utilities run programs for customers who rely on powered medical equipment. California utilities such as PG&E offer Medical Baseline programs. Other examples include Portland General Electric's Medical Certificate and Medical Battery Support, Southern California Edison's Critical Care Backup Battery program, and critical-care customer registration in Texas (for example, CenterPoint Energy). Eligibility is often limited (for example, to high fire-risk areas), so check with your utility.
These programs can mean extra notice before planned shutoffs and outreach during outages. Registration does not guarantee your power stays on. If your utility runs Public Safety Power Shutoffs, see our PSPS and CPAP guide.
Medicare. According to Noridian, a Medicare DME contractor, backup batteries for equipment that can run on AC power are generally not covered (Noridian Jurisdiction A article: AC/DC power adapters and backup batteries). Check with your plan if you have other coverage.
Setup checklist
Do this once, ideally on a calm day rather than the night a storm rolls in.
- Charge the battery fully. The LCD shows the charge percentage.
- Get the right DC cord for your machine. If you're not sure which cord you need, call us at 360-686-7424. Our CPAP DC power cords page lists the options.
- Set the correct output voltage for your CPAP. The battery supports 12V and 24V machines, and the LCD shows the output voltage. This is the first thing to check if your CPAP won't run on the battery.
- Plug the CPAP into the battery and the battery's charger into the wall. You're now in pass-through.
- Leave it that way. Leave it in pass-through every night.
- Know your humidifier settings. Find out now how to turn off the humidifier and heated hose so you can do it in the dark if the power goes out.
More help: connecting your EXP PRO battery to your CPAP machine and why won't my CPAP run on my battery?
Which battery fits your home backup
EXP48PRO APEX
153.6Wh, about 3.25 lb. A good fit if your outages tend to be short and you also travel. It's 153.6Wh, under the published 160Wh carry-on threshold; airline approval and final acceptance still depend on the carrier and security. See the Travel Center. About 2–3 nights with the humidifier and heated hose off. One DC port, plus USB-C for the Breas Z1/Z2, Luna TravelPAP and Transcend Mini/Micro.
EXP96PRO APEX
307.2Wh, about 6.5 lb. Built for multi-night outages and homes with two machines. About 4–6 nights with the humidifier and heated hose off, and two DC output ports. UL 2743 certified and rated IP65. It is not an airline battery. If you also fly, look at the 48: it's 153.6Wh, under the published 160Wh carry-on threshold; airline approval and final acceptance still depend on the carrier and security. See the Travel Center.
Both batteries are LiFePO4, rated for up to 5,000 cycles, carry a 2-year warranty and work with all CPAP and BiPAP machines.
Build your home backup setup: EXP96PRO APEX · EXP48PRO APEX
Not sure which one? Try the battery selection quiz or call 360-686-7424.
Frequently asked questions
Will the battery wake me up when the power goes out?
No. In pass-through your CPAP is already running on the battery, so when the wall power goes out nothing switches. The charger simply stops charging, and the CPAP keeps running on the same battery it was using.
Can I leave it plugged in all the time?
Yes. You can leave it that way all the time. You don't need to save pass-through for nights when an outage is likely.
Does it work with my BiPAP?
EXP PRO batteries work with all CPAP and BiPAP machines. The part that varies is the cord. Call 360-686-7424 with your machine model and we'll make sure you get the right one.
How many nights will I get during an outage?
It's an estimate that depends on your pressure, machine, humidifier and heated hose use, mask leak, battery age and temperature. With the humidifier and heated hose off, expect about 2–3 nights from the EXP48PRO APEX and about 4–6 nights from the EXP96PRO APEX. The runtime calculator at exppropower.com/pages/cpap-battery-runtime-calculator will give you a number for your own setup.
Can I use the humidifier during an outage?
You can, but it uses a lot of power. On the EXP96PRO APEX, running the humidifier and heated hose drops the estimate to roughly one night. If you don't know how long the outage will last, turning them off stretches your battery much further.
Can one battery run two CPAP machines?
The EXP96PRO APEX can. It has two DC output ports, so it can run two CPAP or PAP machines at once. Both machines share its capacity, so each gets fewer nights. You can also connect two of the same EXP PRO battery to double capacity; call 360-686-7424 and we'll walk you through the setup.
Will my CPAP restart on its own after an outage?
With pass-through, it doesn't need to. Your CPAP doesn't lose power when the grid goes down, because it was already running on the battery. It keeps running until the battery runs low.
Is it HSA or FSA eligible?
Coverage rules vary by plan. Check with your HSA or FSA plan administrator before you buy.
Should I get a generator or a battery?
They do different jobs. A generator powers big loads and, per CPSC guidance, must run outdoors, at least 20 feet from the house. A battery runs your CPAP quietly at your bedside all night. Many households use both.
How do I store the battery between outages?
If you keep it in pass-through on the nightstand, that's fine. If you'd rather put it away, store it at 40–50% charge and recharge it at least every 3 months. Charge it to full before you go back to relying on it.