Choosing a Battery

[palerider]

These are good products for someone with deep pockets. The first is nice, assuming you can get it on the plane. However, the second is over $300 plus shipping for only 30 amp-hours. Yes, its nice that its only 8 pounds, but you can have a 35 AH AGM for only $65. It may be 24 pounds, but if you're only lugging it a short distance its not worth it to me to pay 5 times as much! (not that I would be car camping at all!)

For 300$, I could buy *several* lead acid batteries, and a cart to put them in.

[drzman49]

deep pockets is a relative term (LOL). I need to reign it in at times. On the other hand, the price is somewhat offset by the potentially greater lifespan of a lithium battery. People like light and thin laptops and cell phones that are a lot more money than three bills. It really comes down to spouse generosity.

[CapnLoki]

deep pockets is a relative term (LOL). I need to reign it in at times. On the other hand, the price is somewhat offset by the potentially greater lifespan of a lithium battery. People like light and thin laptops and cell phones that are a lot more money than three bills. It really comes down to spouse generosity.

Indeed, deep pockets are relative. Everyone loves getting a new phone, but in my experience more devices get upgraded because the batteries have failed!

Its not clear lithium will last longer than AGM, a lot depends on usage and depth of discharge, etc. If I were using a portable pack often enough to actually wear it out, then the light weight would look really attractive. But since most folks go camping (or need backup) a few times time a year, its more likely a battery will die from neglect than overuse. All my lead-acid batteries (car, boat, backup supplies) tend to last 5 to 7 years, while lithium seem to fade in two years.

The other issue is that you can generally get the full performance specs for lead batteries, which is part of the reason I favor DIY solutions over cheap jump starters. With the new lithium packs you really have no idea what design point was chosen by an anonymous builder in China. You can be sure that if a vendor emerges with an exemplary reputation, they will be the most expensive. Case in point: Tesla has figured out how to get 10 years of daily use from a lithium pack. But that's what drives the high price.

[Hamguy515]

Keep in mind, too, that lead-acid batteries (even those designed/rated for deep-discharge service) are generally not capable of handling greater than 50% depth-of-discharge, while *good* lithium-chemistry deep-cycle batteries are designed for and tolerant of depth-of-discharge approaching 100% of their rated capacity - and many of these lithium packs are rated for twice the number of charge/discharge cycles as a comparable lead-acid battery. This is particularly true with LFP (LiFePO4) batteries, in my experience.

All this combines to mean that you can often spec out a lower capacity lithium battery and still have the same usable capacity available. When taken in the aggregate, your total cost per stored unit of energy PER CYCLE is often less with good-quality lithium packs even though the initial acquisition cost is substantially higher.

[CapnLoki]

Keep in mind, too, that lead-acid batteries (even those designed/rated for deep-discharge service) are generally not capable of handling greater than 50% depth-of-discharge, while *good* lithium-chemistry deep-cycle batteries are designed for and tolerant of depth-of-discharge approaching 100% of their rated capacity - and many of these lithium packs are rated for twice the number of charge/discharge cycles as a comparable lead-acid battery. This is particularly true with LFP (LiFePO4) batteries, in my experience.

All this combines to mean that you can often spec out a lower capacity lithium battery and still have the same usable capacity available. When taken in the aggregate, your total cost per stored unit of energy PER CYCLE is often less with good-quality lithium packs even though the initial acquisition cost is substantially higher.

There's some truth to what you say, but you're cherry picking a bit. And again I'll claim that the "cycle life" issues are often meaningless for cpap users because most folks are looking for something to use a few times a year.

While I'm well aware of the "50% limit" for lead acid, that is only for maximum cycle life. I follow that on my boat batteries because I want the longest lifetime. However, I wouldn't hesitate to run a home backup battery down to 20% because I might only do that once or twice a year. Quality AGM's are rated for repeated deep discharge - the Universal Power Group I often recommend is rated for 200 cycles even at 100% discharge, though with fading capacity:
http://files.upgi.com:8086/UPGFileServi ... heet/D5722
I've seen numerous other specs that list 300-500 cycles down to 20%.

And Lithium has its issues, especially if you're thinking extreme usage, like 3000 cycles. The recommended protocol for Tesla charging is to keep it between about 30% and 80% for long life. The common wisdom is that running 100% to 0% (not actually possible) is guaranteed to induce total failure the day after the warranty expires!

Clearly for applications with daily high discharge (golf carts, etc.) one needs to work out the math. As near as I can tell, there hasn't been a mass conversion yet, but I'd guess the day is coming. I keep looking for 100 AH lithium packs at $150 - I'd certainly jump at that! But I can't justify today's price with "it will pay back in 10 years."

[palerider]

I keep looking for 100 AH lithium packs at $150 - I'd certainly jump at that! But I can't justify today's price with "it will pay back in 10 years."

Then a minor fault causes a thermal runaway and your boat burns down to the waterline.

[Goofproof]

Then the insurance buys you a new boat and battery. Jim

[Thanantos]

I use a lithium battery in my kayak. Some awesome developments for campiing,kayaking, airplaning. My airline American let me take a 222 wh battery, with preauthorization (to use during the flight).
https://www.amazon.com/gp/product/B06ZX ... UTF8&psc=1
3 nights no humidifier

For car camping (carrying battery to tent, don't want to carry a lead acid, this even better, the best with a case with wiring hookups, direct current 12 volt plug, meters:
https://www.amazon.com/gp/product/B01DO ... UTF8&psc=1
at least 5 nights no humidifier

This honestly looks like the ticket for me. I'm camping off my motorcycle for 4 days in Sturgis this year, and this might be perfect. How did you connect the battery to your CPAP?

I have the Philips Dreamstation (not the Go), and I have on it's way the 12v DC cord. Did you modify the cord to use those round 12v outlets in the battery?

Thanks!

[Lane101]

Adding my reply to another thread on this subject - this is one of the most complete discussions on CPAP battery usage that I've seen. Helpful to have everything in one place.

Sharing my experience of successfully camping with CPAP since 2010. Will walk through some key power requirements analysis and outline my DIY modular battery pack & solar system. My CPAP machines for camping include an older Goodknight 420G and newer Philips Respironics PR-150. Pressure setting of 10cm and no humidifier use when camping. Both machines operate directly on 12 volt DC current. If your machine requires AC current then you need the optional inverter noted below.

The critical analysis required for scoping my battery packs was to determine the actual current draw for my machines at the prescribed pressure. In my case (per measurement with an amp meter during operation) the power required was just a fraction of the specifications for each machine. Actual for my 420G is only 0.6 amps versus the 1.5 amps specified on the machine.
In the case of the PR-150 actual is only 0.5 amps versus a 5.0 amp specification. The reason for this is that machine specifications are for the maximum possible current usage - 20CM of pressure in both cases and current for an optional humidifier in the case of the PR-150. Knowing that my power requirements were much more modest than expected allowed me to build a battery pack around a 20 amp hour lead-acid absorbed glass matt (agm) battery that only weighs 13 pounds. Assuming the PR-150 system 0.6 amps for eight hours only uses 4.8 amp hours of current per night allowing my battery pack to support up to 3 nights at a total 75% power drain (below the 80% recommended maximum for agm batteries). In practice, since we charge phones and power some other items with the battery we regularly camp with just one battery for up to two nights. At only $40 per battery I've built two battery packs to cover longer trips and with the solar panel we were able to camp for a full week on Assateague Island last year.

The key message is that you need to determine your specific needs - at higher pressures the larger 35 amp hour U1 batteries may be required to provide the needed current. Also, if your machine requires AC current then you will need an inverter that typically only operates with 80-85% efficiency further increasing power requirements.

My specific set up includes two modular 20 amp hour battery packs and a 30 watt solar panel as follows:

Basic Battery Pack Construction:

1)ExpertPower 12200 12 volt 20 amp hour (ah) agm batteries from Amazon (replaced 7 & 8 year old Powersonic and No-name agms last year that finally aged out) ($40 on Amazon). Note that depending on battery brand you may be able to save significantly by dropping down to an 18 amp hour battery if it meets your requirements. Just remember that maximum agm recommended cycle use is 80% of capacity or 16 out of 20 amp hours for my battery or just 14.4 amp hours from 18 ah of capacity.
2)EP Auto 10 gauge in line ATC auto fuse holder on the positive terminal of each battery with a 15 amp auto ATC fuse (protects main wiring and battery from short circuit - $10 for a pack of 10 on Amazon)
3)Permanent 12 gauge 100% copper JSC Cable auto zip wire for main battery cable (20 amp rating) attached to in-line fuse holder and negative battery terminal. About 2 feet long with Anderson powerpole connectors. (Price will vary based on brand and quantity, $10 for a pack of 10 powerpole connectors)
4) 2.1mm barrel connector cable (18 gauge) with added Anderson Powerpole connectors. Barrel connector for the CPAP machine while the powerpoles connect to the main battery cable. Also have a 5 AMP fuse on this to protect narrower gauge cable and my CPAP machines. PR-150 machine use requires a 2.1mm to 2.5mm barrel connector adaptor. (About $6 for cable and connectors).
5) The battery is in a cheap Harbor Freight Plastic Ammo box (just the bottom) with the entire system carried in a small size heavy cloth tool bag (breathable for battery - $4 for box and $10 for bag).
6) All connections are covered with electrical tape and/or heat shrink tubing to minimize the chance of a short circuit.
7) Battery charger, I currently use a 3amp 3 stage Deltran Battery Tender Power Plus available at Costco for $39 ($29 when on sale). Started with a $10 generic 1 amp charger that did what was needed - just took longer.

The above is all that is needed for operation of my CPAP and is all you need to cover 2 - 3 nights of camping based on your machines power requirements. If you only want to run your CPAP and skip the inverter and solar option (see below) you can connect the 18guage barrel connector cable (with 5 amp in-line fuse) directly to the battery (use inexpensive O-ring connectors on the battery terminals) and skip the auto zip wire (all for under $75-80 with a low cost charger).

To power other items and charge phones I've also added the following optional items (and a 2nd 20 amp hour battery pack for trips of 3 - 4 nights):

An Ampeak 400 watt inverter ($30 on Amazon - replaced a 7 year old Harbor Freight version last year). Make sure you get the newer version with user replaceable fuses. If your CPAP requires AC power, and can operate on a modified sine wave inverter, you will need this. I successfully tested an older ZZZpap unit (use at home) on this and it worked well. Occasional inverter use is why I've over spec'd the main battery cable. Supporting the inverter with up to 180 watts of power (15amp fuse) is why I've used the 12 gauge auto zip wire. Note that for a 20 amp hour battery you should not use items that require more than roughly 5 amps (60 watts) on a regular basis. If you need more wattage for non-CPAP devices consider a larger battery. Always use a fuse on step below wire capacity - in this case 15 amp fuse for wire spec'd at 20 amps.
9) Also purchased a NOCO gc018 cigarette lighter style power adapter. Replaced the ring connectors with Anderson powerpoles. Use this for an air mattress inflator. This comes with an replacable auto fuse that I downgraded to 7.5amps for greater safety. Also use this with an auto cigarette lighter socket phone charger.

The solar panel for longer camping trips includes:

10) A Newpowa NPA30-12 30 watt solar panel ($42 on Amazon)
11) Basic 5 amp waterproof solar charge controller ($14 from Amazon)
12) Mini-blade in-line fuse holder with 5 amp fuse to protect panel from a battery short circuit (on positive that connects to battery-$4)
13) 10 feet of 16 gauge wire rated for outdoor use with anderson powerpoles added to connect battery to solar panel (under $5).

The charge controller and fuse are mounted on the solar panel to make this an easy to use modular unit that quickly connects to the battery packs. In full sun at panel output is 1.75 amps - charging a 50% discharged 20 amp hour battery in under 6 hours. With this and the two battery packs we ran my CPAP and a fan that drew 0.4 amps every night in addition to charging our cell phones while at Assateague. Note that on Assateague in summer we got optimal sun of 10 -12 hours of charging possible each day. You may want a larger panel for use in areas or during seasons where there is less sunlight.

Bottom line is that with the above modular approach you can get started for under $75 and expand as needed and only bring what is required for each specific camping trip. Key is to measure your actual power usage so you can scope this to what you need. Also make sure you add adequate fusing to protect from short circuits and use the right connectors, electrical tape to ensure no bare wires or connections. Have seen too many "how-to's and videos that skip this.

Note that maintenance requirements are minimal. Off-season you should top off the battery charge every 3 months. I also run the battery through a modest 25% usage/recharge cycle after 6 months of storage. This setup also does well as a back-up in case of power failure.

[laprof]

Hello! I want a battery that weighs less than 5 lbs and is as small as possible. When I travel, I would prefer not to be carrying a heavy battery around. I am looking for a battery for my Resmed 10 airsense for when there are power outages (due, mainly, to thunder storms where I travel in the summer and fall), so not an every night need (hopefully!). Looking online, I've found relatively reasonably priced ones to exorbitantly priced ones (over $1500), and they all state that a converter is needed... plus heaven knows what else! I don't mind paying a couple hundred dollars, but won't pay $1500! I do use a humidifier (set usually at "1", but could do w/o it, I guess, in an emergency. Since I'm at a complete loss as to which ones I should consider seriously and since I've read that you are the expert, I'm hoping you'll be able to direct me... Thank you for your time. Below is a battery that I think might be okay that I found on shopcpap.com (Also, I'd like to be able to use it on long distance flights.)

C-100 Travel CPAP Battery Pack
C-100 CPAP Battery Pack
$ 279.00
More Info

[Pugsy]

Might want to add to you wants list is a battery that can be used on the airplane for long flights if that is also a requirement.
That little tidbit puts a significant monkey wrench into things.
Airlines have a size limit in terms of watt hours for lithium batteries (the only way you can get the weight down). I think it is under 100 but always check with the airlines to be sure.

The converter is needed because ResMed machines use 24 volts and most batteries put out 12 volts...so you need something to change 12 volts to 24 volts.
Now there are some battery packs specifically designed for ResMed requirements and they have the converter built into the system....but they are more costly. You pay for it one way or the other.

All this comes at a price though....the more of your want list it fills...the bigger the price tag...
and you also want it to take care of your needs during power outages at your destination.

Post by laprof » Thu May 30, 2019 12:50 pm
Hello! I want a battery that weighs less than 5 lbs and is as small as possible.

[CapnLoki]

Hello! I want a battery that weighs less than 5 lbs and is as small as possible. When I travel, I would prefer not to be carrying a heavy battery around. I am looking for a battery for my Resmed 10 airsense for when there are power outages (due, mainly, to thunder storms where I travel in the summer and fall), so not an every night need (hopefully!). Looking online, I've found relatively reasonably priced ones to exorbitantly priced ones (over $1500), and they all state that a converter is needed... plus heaven knows what else! I don't mind paying a couple hundred dollars, but won't pay $1500! I do use a humidifier (set usually at "1", but could do w/o it, I guess, in an emergency. Since I'm at a complete loss as to which ones I should consider seriously and since I've read that you are the expert, I'm hoping you'll be able to direct me... Thank you for your time. Below is a battery that I think might be okay that I found on shopcpap.com (Also, I'd like to be able to use it on long distance flights.)

C-100 Travel CPAP Battery Pack
C-100 CPAP Battery Pack
$ 279.00
More Info

Sorry about the delayed reply - its boat launching season which has me a bit pre-occupied.

I don't like to give recommendations on Lithium packs because the market is shifting quickly and frankly I've never bought one for a cpap, and generally have had mixed feelings about the smaller ones I've used for cell phones. Please do your "due diligence" before any purchase. That said ...

There are three basic approaches for Lithium packs. Remember that for airline use you have to stay below 100 watt-hours, so that means a small pack
1. A generic small pack oriented towards cell phones. These will sometime say "32000 miniamp-hours," a rather bogus marketing claim. The are around $120 and may work for you. You will need the 12-24V converter for Resmed.

2. A fancy version of the above, but designed for cpaps - the C-100 is one example, the Freedom (an update of the c100) and the Medistrom Pilot-24. The cost of the special design is high - they are around $300. The Pilot 24 has the advantage of having a cable that works with ResMed directly, so you don't need the converter.

3. There are now larger Lithium packs, up to 400 or 500 watt-hours that may cover several days or the higher load of a humidifier. Very handy for camping, but not legal to take on a passenger plane.

Other things to think about - the new Resmed uses almost twice the power of older machines. In particular, you could get a Respironics machine as a travel/backup that would go twice as long on the same battery. Also, you could use a cheap AGM battery for your summer location, and a small lithium for airline travel. Frankly that would be my solution, if I ever decided to use a cpap on a plane.

[Hamguy515]

Hello! I want a battery that weighs less than 5 lbs and is as small as possible. When I travel, I would prefer not to be carrying a heavy battery around. I am looking for a battery for my Resmed 10 airsense for when there are power outages (due, mainly, to thunder storms where I travel in the summer and fall), so not an every night need (hopefully!). Looking online, I've found relatively reasonably priced ones to exorbitantly priced ones (over $1500), and they all state that a converter is needed... plus heaven knows what else! I don't mind paying a couple hundred dollars, but won't pay $1500! I do use a humidifier (set usually at "1", but could do w/o it, I guess, in an emergency. Since I'm at a complete loss as to which ones I should consider seriously and since I've read that you are the expert, I'm hoping you'll be able to direct me... Thank you for your time. Below is a battery that I think might be okay that I found on shopcpap.com (Also, I'd like to be able to use it on long distance flights.)

C-100 Travel CPAP Battery Pack
C-100 CPAP Battery Pack
$ 279.00
More Info

Some may disagree with my selection, but I've settled on two separate batteries for now. Which I use depends upon my need and requirement for portability.

My first battery is the Medistrom Pilot 24-Lite used only with my AirMini, and only when I'm on a weekend or overnight backpacking/primitive camping trip. The case for this battery is a bit heavy, so I may look at building my own pack for further weight savings, but the entire package (including the AirMini) clocks in right at 2 lbs total. My secondary reason in selecting this battery is that it is specifically designed and labeled to accommodate air travel. Capacity is 98Wh.

My second battery is a Bioenno LiFePO4 12V/12Ah pack (https://www.bioennopower.com/collection ... -blf-1212w) Larger capacity versions are available, but I felt this was a good compromise for my needs. It allows me to effectively use my normal AirCurve VAUTO (sans humidifier) for a full weekend without being tied to AC mains, or for an almost indefinite period when recharging via a portable 120W solar panel I already owned (https://www.powerfilmsolar.com/products ... olar-panel). The battery clocks in at 3.3 lbs and the solar panel (if I take it along) is another 6.3 lbs. I can comfortably recharge the battery on a typical day with no issues, and not have to worry about finding ideal conditions or panel orientation. I've considered working this battery and a dedicated charge controller into a permanent in-home battery backup solution, but for now, it's just a portable standalone option.

I will acknowledge that neither solution is a "budget" one, however, they work for me.

[psteckler]

I've asked elsewhere, but got no reply. So I'll ask in this thread: what is the polarity of the DC output of the Medistrom Pilot-24 Lite? Is it center-positive, or center-negative?

[Goofproof]

I've asked elsewhere, but got no reply. So I'll ask in this thread: what is the polarity of the DC output of the Medistrom Pilot-24 Lite? Is it center-positive, or center-negative?

I don't have one but I'll bet the unit has a pos and neg, that attaches with a cable to the XPAP, each cable is made for a different machine and would match the needs. The cable wiring should match what you are using it on. Jim