New Battery and Amp-Hour Data

[CapnLoki]

Well, I think I'll just go ahead and purchase the same setup - hopefully you're getting some sort of kickback!

Well, it did occur to me that I could open an online store and make a few pennies ...

We are staying in an RV for a week in Yosemite; we will have occasional access (if necessary) to it's generator, but would prefer to charge the battery during the 1-2 hour car rides we'll be taking to other parts of the park (those generators can be loud!). Does this sound like a feasible plan, or is driving with the battery (possibly in hot weather) not such a great idea?

Thanks again,
Kate

Shouldn't be a problem. If you don't run the humidifier, you're only topping off the battery, and any vehicle that can haul an RV will have enough extra horsepower so that an extra few Amps won't be a problem. But you raise an issue that most people wouldn't consider: on my boat, if the house batteries (450 Amp-hours!) are depleted when I'm powering, I have to throttle back the alternator because at its full 100 amp output it adds about 5 HP load to the small diesel which only has 18 HP, so it could easily overheat. And if you're hauling a heavy RV up hills with the A/C running, I'm sure you'll have one eye on the temperature gauge ...

[Thanantos]

I know this is a very old post, but it's awesome information.

My question is about the amp hour usage. Am I reading this correctly to say that the first test used 4 amp hours total for 8 hours?

My motorcycle battery is 30 amp hours so that would mean I'd be ok using that to power my CPAP for a couple overnight trips?

[CapnLoki]

I know this is a very old post, but it's awesome information.

My question is about the amp hour usage. Am I reading this correctly to say that the first test used 4 amp hours total for 8 hours?

My motorcycle battery is 30 amp hours so that would mean I'd be ok using that to power my CPAP for a couple overnight trips?

It sounds like it should work. You don't mention your gear, but many cpaps run on 12V will only use 4 AH a night. Of course, if you use an inverter, or high pressure the load will be higher. And some newer machines use more power, so you could easily get up to 7 or 8 ah a night.

Also two caveats: first, some lithium motorcycle batteries batteries are rated in "pb-eq" where they over-rate the lithium on the grounds that lithium outperforms in starting applications. They are claiming, for example, that a 7 AH lithium is equivalent to 20 AH, which is not true for cpap powering. This means anyone with a lithium pack should double check that the stated rating is true amp-hours.

The other issue is that you want to make sure you can start the bike in the morning. If you can reliably kickstart (or bumpstart) it isn't a big risk, but its certainly possible that two cpap nights on an old battery can drop the voltage below the point where it could turn over a big engine. Especially if the the battery is a "starting battery" not designed for deep discharge - such starting batteries considered too depleted to start at 70% State of Charge, which is roughly where you'll be after two nights.

So there's a few issues to consider: make sure the battery is a new, true 30 AH deep cycle. Double check the actual load of your gear. And make sure you can start if the calculations go awry.

[Goofproof]

There is also the fact that if you drain a lead acid, past a certain point the number of recharge cycles you can get out of the battery drop much faster. A Lith Ion Battery will be damaged also, but you can discharge it much deeper and still maintain many recharge cycles, way more than lead acid. Jim

[Thanantos]

I know this is a very old post, but it's awesome information.

My question is about the amp hour usage. Am I reading this correctly to say that the first test used 4 amp hours total for 8 hours?

My motorcycle battery is 30 amp hours so that would mean I'd be ok using that to power my CPAP for a couple overnight trips?

It sounds like it should work. You don't mention your gear, but many cpaps run on 12V will only use 4 AH a night. Of course, if you use an inverter, or high pressure the load will be higher. And some newer machines use more power, so you could easily get up to 7 or 8 ah a night.

Also two caveats: first, some lithium motorcycle batteries batteries are rated in "pb-eq" where they over-rate the lithium on the grounds that lithium outperforms in starting applications. They are claiming, for example, that a 7 AH lithium is equivalent to 20 AH, which is not true for cpap powering. This means anyone with a lithium pack should double check that the stated rating is true amp-hours.

The other issue is that you want to make sure you can start the bike in the morning. If you can reliably kickstart (or bumpstart) it isn't a big risk, but its certainly possible that two cpap nights on an old battery can drop the voltage below the point where it could turn over a big engine. Especially if the the battery is a "starting battery" not designed for deep discharge - such starting batteries considered too depleted to start at 70% State of Charge, which is roughly where you'll be after two nights.

So there's a few issues to consider: make sure the battery is a new, true 30 AH deep cycle. Double check the actual load of your gear. And make sure you can start if the calculations go awry.

Thanks for your detailed reply to my, sadly, poorly detailed question.

I have a Philips Respironics Dreamstation (not the Go version), and I plan to not use the humidifier. The bike is a Harley Ultra Classic with a lead acid battery.

You've given me much to consider here. Thanks!

[CapnLoki]

Thanks for your detailed reply to my, sadly, poorly detailed question.

I have a Philips Respironics Dreamstation (not the Go version), and I plan to not use the humidifier. The bike is a Harley Ultra Classic with a lead acid battery.

You've given me much to consider here. Thanks!

I haven't done a detailed test of my new Dreamstation, but it seems to have a similar load as my older 560.

I should add the my general advice is to never use your only starting battery as cpap battery. The smaller bike battery would also argue for this. However, the ability to start without a battery (do you have a kickstart?) helps. For car owners I usually say just put a deep cycle battery in the trunk, but on a bike that's easier said then done! The best bet may be a small lithium power pack. They are measured in "watt-hours", where 60 watt-hours are roughly 5 amp-hours at 12 volts. There are many small ones at about 100 watt-hours, an FAA limit, and there are newer packs up to 250 watt-hours for camping that may be appropriate.

[Thanantos]

Thanks for your detailed reply to my, sadly, poorly detailed question.

I have a Philips Respironics Dreamstation (not the Go version), and I plan to not use the humidifier. The bike is a Harley Ultra Classic with a lead acid battery.

You've given me much to consider here. Thanks!

I haven't done a detailed test of my new Dreamstation, but it seems to have a similar load as my older 560.

I should add the my general advice is to never use your only starting battery as cpap battery. The smaller bike battery would also argue for this. However, the ability to start without a battery (do you have a kickstart?) helps. For car owners I usually say just put a deep cycle battery in the trunk, but on a bike that's easier said then done! The best bet may be a small lithium power pack. They are measured in "watt-hours", where 60 watt-hours are roughly 5 amp-hours at 12 volts. There are many small ones at about 100 watt-hours, an FAA limit, and there are newer packs up to 250 watt-hours for camping that may be appropriate.

Cool, that fits with what I've found. Since I can use HSA money for my "battery backup system" I think I'm going to go with the Suaoki 222wh system.

Thanks for your help!

[Jack Burton]

Cool, that fits with what I've found. Since I can use HSA money for my "battery backup system" I think I'm going to go with the Suaoki 222wh system.

My Resmed S9 with humidifier draws ~85 watts.
222 / 85 = 2.6 hours
without the humidifier it draws ~25 watts.
222 / 25 = 8.9 hours

Also the watt hour ratings for the solar generator/power station products are usually beyond optimistic.

The 440 watt hour version https://www.amazon.com/Portable-Generat ... 60BAN?th=1 indicates that it has a 80% depth of discharge rating.
440 * 0.8 / 25 = 14.1 hours

Hope this helps.

[CapnLoki]

My Resmed S9 with humidifier draws ~85 watts.
222 / 85 = 2.6 hours
without the humidifier it draws ~25 watts.
222 / 25 = 8.9 hours

Also the watt hour ratings for the solar generator/power station products are usually beyond optimistic.

The 440 watt hour version https://www.amazon.com/Portable-Generat ... 60BAN?th=1 indicates that it has a 80% depth of discharge rating.
440 * 0.8 / 25 = 14.1 hours

Hope this helps.

Something is off in your numbers. Assuming you're running from a 12V source with the 12/24 converter, 85 watts is about 7 amps or 56 amp-hours for a night. 25 watts is 2 amps, or 16 amp-hours for a night. This is about double the worst case load, and about 4 time the average load (assuming pressure 10, moderate humidity). Are you using an inverter and measuring with a Kill-a-Watt?

[Jack Burton]

Are you using an inverter and measuring with a Kill-a-Watt?

120 volt mains ac power, measured with blue planet em100 -- https://www.amazon.ca/UPM-Marketing-EM1 ... B000RKVK52.
RX 10-20 tested with "mask test" and humidity at max.

UPDATE:
I just tested again got ~20 watts with the mask fit test and max humidity.
I think I must have been testing with a heated hose.
Not sure how I got 25 watts without a humidifier though.

[Thanantos]

Sorry guys, I'm new to this math.

So, if I charged the device everyday on the motorcycle do you think the 222wh battery would work with no humidifier or heated tube?

[CapnLoki]

Are you using an inverter and measuring with a Kill-a-Watt?

120 volt mains ac power, measured with blue planet em100 -- https://www.amazon.ca/UPM-Marketing-EM1 ... B000RKVK52.
RX 10-20 tested with "mask test" and humidity at max.

UPDATE:
I just tested again got ~20 watts with the mask fit test and max humidity.
I think I must have been testing with a heated hose.
Not sure how I got 25 watts without a humidifier though.

But you are running through an inverter - this has little relevance to running on DC power.

[CapnLoki]

Sorry guys, I'm new to this math.

So, if I charged the device everyday on the motorcycle do you think the 222wh battery would work with no humidifier or heated tube?

Since your pump will use only about 50-60 watt-hours a night, it should cover 2-3 nights easily without recharge. If you can hook it up to your bike and charge while riding, you could extend that significantly. If you want to do long trips, you should get a battery that has a meter so you can tell how you're keeping up. One problem is that a full charge may be time consuming, like 5 hours to get to 90%, another 12 to really top off. However, since you have overkill with the battery, it may work out. (On my boat the battery is sized for 3 days use, and I run it down to 50% and back up to 85% daily, staying in the sweet spot for optimal charging and minimal wear.)

BTW, I assume you're thinking of keeping your starting battery and adding a lithium pack.

[Thanantos]

Sorry guys, I'm new to this math.

So, if I charged the device everyday on the motorcycle do you think the 222wh battery would work with no humidifier or heated tube?

Since your pump will use only about 50-60 watt-hours a night, it should cover 2-3 nights easily without recharge. If you can hook it up to your bike and charge while riding, you could extend that significantly. If you want to do long trips, you should get a battery that has a meter so you can tell how you're keeping up. One problem is that a full charge may be time consuming, like 5 hours to get to 90%, another 12 to really top off. However, since you have overkill with the battery, it may work out. (On my boat the battery is sized for 3 days use, and I run it down to 50% and back up to 85% daily, staying in the sweet spot for optimal charging and minimal wear.)

BTW, I assume you're thinking of keeping your starting battery and adding a lithium pack.

Right, and thanks for the help. I pulled the trigger on the lithium battery pack, and I plan to use it like you said.

I'll use it to power the CPAP overnight, and then I'll charge it on the motorcycle when we ride during the day. It's only a 4 night camping trip so I'm confident this will work.

I will report back my results though so others can benefit from my experience.

[Goofproof]

You might try using it at home, without charging to see what the real usage time is for a fully charged pack first. Jim

Giving you a Best Case Idea.