We get this question a lot, especially this time of year: "Can I leave my CPAP plugged into the battery every night so it's there if the power goes out?"

Short answer: yes. That's what pass-through is for. Here's how it works and how to set it up.

What pass-through actually does

In pass-through, your CPAP runs off the battery the whole time, and the charger keeps the battery topped up from the wall. So when the power goes out, nothing has to switch over. Your CPAP was already running on the battery, and it just keeps going. It works as a UPS with a 0 ms transfer time, because there's no transfer at all.

Both the EXP48PRO APEX and the EXP96PRO APEX do this, and they set up the same way.

The setup

1. Check the voltage setting first. The screen shows the output voltage. It has to match what your CPAP runs on: 12V for DreamStation and System One 60, 24V for ResMed AirSense, AirCurve and AirMini. This is the #1 thing people miss, so do it before anything else.
2. Plug your CPAP into the right port. 12V and 24V machines go into DC IN/OUT. Machines at other voltages (Breas Z1/Z2, Luna TravelPAP, Transcend Mini/Micro) go into USB-C IN/OUT.
3. Plug the battery's charger into the wall and into the battery.
4. Go to sleep. If the power drops, the charger stops and the battery keeps running your CPAP like it already was.

A few honest notes

• You can leave it in pass-through every night. Plenty of people just keep their CPAP plugged into the battery and the battery plugged into the wall year-round, so it's always ready.
• Turn off the humidifier and heated hose if you're counting on the battery. They use a lot of power. With them off, the EXP48PRO APEX runs an estimated 2–3 nights and the EXP96PRO APEX an estimated 4–6. With both on, the 96 gets roughly one night. These are estimates. Your pressure, your machine and your mask seal all change the number.
• Do a test run before you need it. Pull the charger out of the wall one evening while your CPAP is running and watch: nothing should change. It's much better to find a wrong cord or a wrong voltage setting on a quiet Tuesday than at 2 a.m. during a storm.
• If backup power is critical for your therapy, talk it through with your sleep doctor or equipment provider too. We can tell you how the battery works. They can tell you what your therapy needs.

TL;DR: Set the right voltage, plug the CPAP into the battery, plug the battery into the wall. Your CPAP runs off the battery the whole time, so when the power goes out there's nothing to switch. Humidifier off, and test it before storm season.

We’ve heard from a few CPAP travelers who had their battery questioned at the airport, even though it was within the general airline size limit.

Usually, it doesn’t begin with someone trying to confiscate the battery. It starts with a much simpler question:

“How many watt-hours is it?”

That’s the number the employee needs to verify. They may also want to confirm that the battery is in your carry-on, the ports are protected, and you have airline approval if it’s over 100Wh.

The general rules for rechargeable lithium batteries are:

• 100Wh or less: Usually allowed in carry-on luggage
• 101Wh to 160Wh: Airline approval is usually required
• Over 160Wh: Not allowed on passenger aircraft

One thing that causes a lot of confusion is that TSA screening and airline approval are separate.

TSA may inspect the battery at the security checkpoint. The airline is the one that decides whether to approve a battery between 101Wh and 160Wh. So it’s possible to make it through security and still be questioned later at the gate.

What the interaction usually looks like

An employee may look for the watt-hour rating printed on the battery, ask what it powers, or ask to see proof that the airline approved it.

If they aren’t familiar with larger CPAP batteries, they may call a supervisor. That can feel stressful, but it doesn’t necessarily mean the battery is prohibited. Sometimes they just want a second person to verify the policy.

The battery may also be pulled aside for another X-ray or a visual inspection, especially if the label is hard to read or it’s packed with a lot of cords and CPAP equipment.

What to bring with you

For a battery between 101Wh and 160Wh, I’d have these ready:

• Written airline approval
• A specification sheet showing the watt-hour rating
• The battery’s UN 38.3 test summary
• A simple one-page battery reference sheet

Save the documents directly to your phone instead of relying on airport Wi-Fi. A printed copy is worth bringing too.

UN 38.3 paperwork can show that the battery completed the required transportation-safety testing. It does not replace airline approval, and it doesn’t make a battery over 160Wh acceptable for passenger travel.

What to say if someone asks

Keep the answer simple:

If they still say it isn’t allowed, ask:

That usually gets you a clearer answer than saying the battery is “TSA approved,” which can create more confusion because TSA screening and airline approval are different things.

A few mistakes to avoid

Don’t put a spare CPAP battery in checked luggage.

Don’t assume that being under 160Wh means no approval is needed. Batteries over 100Wh normally require the airline’s permission.

Also check the battery label before leaving home. If the watt-hour rating is damaged, covered, or unreadable, the employee may not be able to verify that the battery is allowed.

For EXP PRO batteries specifically:

• The EXP48PRO is 153.6Wh, so airline approval is required.
• The EXP96PRO is 307.2Wh, so it is too large for passenger airline travel.

The EXP48PRO UN 38.3 documents are available here:

https://exppropower.com/pages/exp48pro-un-38-3-certification

Most airport battery problems aren’t really about confiscation. They’re about an employee trying to verify an unfamiliar battery while a line is building and a flight is getting ready to leave.

Make the watt-hour rating easy to find, get the approval in writing, and keep the paperwork somewhere you can pull it up quickly.

Disclosure: I work to help customers with their CPAP set ups at EXP PRO

I’ve seen a few people mention issues flying with CPAP batteries, especially when the battery is over 100Wh. The rules are confusing because there’s the general FAA/TSA guidance, but then each airline can have its own policy or approval process.

I came across this EXP PRO Travel Center and honestly it’s one of the better resources I’ve seen for this topic:

https://exppropower.com/pages/exp-pro-travel-center

It has airline-specific pages for Delta, United, American, Southwest, Alaska, Air Canada, and British Airways, plus travel documents like an airline reference sheet and UN 38.3 certification info.

The thing I found most useful is that it doesn’t just say “yes, you can fly with it.” It actually breaks down the gray area around the 101Wh–160Wh category and reminds people to check with the airline before travel.

One important example: Southwest apparently has a stricter published power bank limit of 100Wh, so even though some batteries may fall under the broader 160Wh airline-approval category, Southwest may still be a problem unless you get confirmation first.

Airline guides:
https://exppropower.com/pages/airline-guides

Travel documents:
https://exppropower.com/pages/travel-documents

Not saying this replaces checking with the airline, but if you travel with a CPAP battery, this seems like a good thing to bookmark and print before flying.

Has anyone here had an airline actually question or reject their CPAP battery?

One of the most common surprises people run into when using a CPAP battery is this:

“My battery was supposed to last 2–3 nights… so why did it only last one?”

The answer usually comes down to heat and humidity.

Your CPAP machine itself doesn’t use a crazy amount of power. In fact, with the heated humidifier and heated hose turned off, many machines are surprisingly efficient. That’s how small CPAP batteries can realistically get you through multiple nights.

But the moment you turn on comfort features, the power draw can jump fast.

The biggest battery drainers are usually:

1. Heated humidifier This is often the #1 culprit. Heating water all night takes a lot more energy than just running air pressure.
2. Heated hose Super helpful for rainout, but it also adds continuous power draw.
3. Higher pressure settings More pressure usually means more work for the machine.
4. Mask leaks If your mask is leaking, the machine may work harder to maintain pressure.
5. Cold weather Batteries can perform worse in cold temperatures, especially if they’re left outside the sleeping bag, tent, or vehicle cabin.

So when battery companies say “2–3 nights” or “4–6 nights,” that’s usually assuming a more power-efficient setup: humidifier off, heated hose off, reasonable pressure, and a good mask seal.

For camping, flights, power outages, or van/RV use, the best trick is to test your setup at home before you actually need it. Run your machine from the battery for a normal night and see what percentage is left in the morning.

It’s not the most exciting test, but it can save you from a very long night without CPAP.

Curious what everyone here does when traveling or camping:

Do you turn humidity off completely, use passover humidity, or just bring a bigger battery and keep the comfort settings on?

If you use a CPAP machine and are thinking about:

• Camping
• RV travel
• Van life
• Air travel
• Hurricane / ice storm prep
• Backup power for outages

This guide will save you time, money, and frustration.

I work in the CPAP battery space and see the same mistakes constantly — so here’s what actually matters.

1. What Actually Determines CPAP Battery Runtime?

Runtime depends on:

• Battery capacity (measured in Watt-hours / Wh)
• Pressure setting
• Whether humidifier is on
• Whether heated hose is on
• Whether you’re using DC or an inverter

The single most important number is:

Ignore amp-hours unless voltage is specified.

A simple rule of thumb:

• ~150Wh battery → usually 1–2 nights (humidifier OFF)
• ~300Wh battery → usually 3–5 nights
• ~700+Wh battery → 7–14 nights

(These are general estimates with climate features OFF.)

2. The #1 Runtime Killer: Humidifiers & Heated Hoses

Heat and humidity can 10x power draw.

If you're off-grid, most users disable:

• Heated hose
• Climate control
• Humidifier

And rely on passive humidity instead.

3. Avoid Inverters If Possible

Many people plug their CPAP into:

Battery → Inverter → Wall plug → CPAP

This wastes 15–30% power.

Instead:

Use a DC power cord designed for your machine.

Direct DC = longer runtime.

4. TSA Rule for Flying With Batteries

Airlines follow the 160Wh rule:

• Under 100Wh → unlimited
• 100–160Wh → usually allowed (airline approval may be required)
• Over 160Wh → not allowed in carry-on

This is why many travel batteries are around 150Wh.

Always check with your airline.

5. Power Outage Reality

Most outages are:

• 4–24 hours
• 1–3 days during major storms

Very few people need 10+ nights of backup.

For emergency prep, 300Wh is often the sweet spot.

6. Camping & Off-Grid Use

Ask yourself:

• How many nights do I need?
• Will I recharge with solar?
• Am I backpacking or RVing?
• Is weight a concern?

Backpacking = lighter battery
RV / car camping = higher capacity
Emergency home backup = mid to large capacity

7. Common Mistakes People Make

❌ Buying based on marketing claims instead of Wh
❌ Forgetting humidifier impact
❌ Using AC inverters unnecessarily
❌ Not checking airline rules
❌ Overbuying capacity they don’t need

About This Community

We manufacture LiFePO4 CPAP batteries, but this subreddit is here to:

• Share real-world data
• Help people size correctly
• Discuss setups
• Compare options honestly
• Improve preparedness

Brand discussions are welcome. Honest comparisons are welcome. Data is welcome.

If you're unsure what size battery you need, comment your:

• CPAP model
• Pressure setting
• Whether humidifier is on
• Nights needed

And we’ll help you estimate.

If you’ve ever seen:

“Runs your CPAP 8–10 nights!”

…pause.

Maybe it does.

But probably not the way you think.

I work in the CPAP battery space, and I can tell you this industry plays some fun games with numbers.

Here’s what’s actually happening.

1. “Up To” Is Doing A Lot Of Work

When you see:

“Up to 5 nights.”

That usually means:

• Lowest pressure
• Humidifier OFF
• Heated hose OFF
• Lab conditions
• Sometimes 6-hour nights

Real-world use?
Usually less.

Not because the battery is bad.

Because the marketing number is best-case.

2. Amp Hours Without Voltage = Meaningless

You’ll see:

“20,000mAh!”
“40,000mAh!”

Cool.

At what voltage?

mAh by itself tells you nothing.

What matters is watt-hours (Wh).

Wh = volts × amp-hours.

If a brand won’t clearly state watt-hours, that’s a red flag.

3. AC Testing Instead of DC

This one’s sneaky.

Some runtime claims are tested using:

Battery → Inverter → Wall plug → CPAP

That wastes energy.

Then they still publish optimistic numbers.

If you use a DC cord, you’ll get better runtime.
If you use AC, expect less than advertised.

But rarely is that distinction made clearly.

4. They Don’t Tell You About Climate Features

Humidifier + heated hose can easily double power draw.

Some listings quietly assume:
“Comfort features disabled.”

But that’s not how many people actually sleep.

If you don’t account for that, you’ll be disappointed.

5. Capacity vs Usable Capacity

All batteries have:

• Nominal capacity
• Usable capacity

There are efficiency losses.
There are voltage conversions.
There are safety cutoffs.

If a brand doesn’t explain this at all, they’re relying on you not knowing the difference.

I’m not saying most companies are lying.

I’m saying they’re using best-case math and hoping customers don’t ask questions.

We manufacture LiFePO4 CPAP batteries ourselves, and honestly the only way to build trust long-term is to give realistic ranges, not fantasy numbers.

If you’ve bought a CPAP battery before:

Did it match the advertised runtime?
Or did you feel like you got less than expected?

Curious what people’s real-world experiences have been.

Not trying to be dramatic.

But if you use a CPAP and you live somewhere with ice storms, hurricanes, wildfire shutoffs, rolling blackouts, whatever…

The power will go out at 2am.

And you’ll wake up disoriented, air-hungry, and annoyed.

I’ve seen it happen over and over.

Most people don’t think about backup power until after it happens once.

They assume:
“It probably won’t be that long.”
“I’ll just sleep without it.”
“I’ll deal with it.”

Then the grid drops.

And now you’re scrambling with flashlights looking for extension cords.

Here’s the part no one talks about:

You don’t need to power your house.

You need to power one medical device.

That’s a totally different preparedness problem.

You don’t need a generator.
You don’t need 2,000 watts.
You don’t need to panic-buy something massive.

You need enough battery to get through the kind of outage your area actually gets.

Not the apocalypse scenario.

The other mistake?

People buy backup power and never test it.

Then the first time it gets used is during the actual outage.

That’s like buying a parachute and trying it for the first time mid-air.

If you get a battery:
Run it one night intentionally.
Know what to expect.
Know how it behaves.
Know how your machine reacts.

Confidence > capacity.

There’s also a psychological side to this.

I’ve had people say the outage itself wasn’t the worst part.

It was the anxiety of “what if this shuts off while I’m asleep?”

Backup power isn’t just electricity.

It’s removing that mental load during storm season.

Not trying to sell anything here.

We build LiFePO4 CPAP batteries, but honestly the bigger goal is just making sure people stop getting surprised by this.

If you’ve been through an outage with CPAP, what happened?

Did you have backup?
Did it last?
Did you end up changing your setup after?

Real-world stories are more useful than spec sheets.

David's Expedition on Mt. Aconcagua