New Battery and Amp-Hour Data

[JHC]

I'm new but I've read the key threads and many others following up on them. I have an AirSense 10, and it runs at an average of 12.2 lbs pressure. The battery guide's table, after I round up instead of down, says that in one night it'll draw:

Using DC Converter:
15 AH with no humidification or heating. (I wouldn't want to fool with the water while camping, although I usually like the humidity and I might need it where I'm going -- Monument Valley.)

Using an Inverter:
It doesn't say, for the AirSense 10. But comparing the converter and inverter charts for other models, it looks like an inverter has about 65% of the efficiency of a converter. So I need maybe 23 AH?

222 Watt-Hours @12v=18.5 AH. So it looks like the SUAOKI 222Wh Power Station would NOT do the job if I use the inverter with my existing cord and brick, but it WOULD do the job if I get the DC-DC 12-to-24 converter.

But I am very new at all these terms and calculations, so I'd like guidance about both of those conclusions. I really was hoping that the Suaoki, without any extra equipment, would be adequate, and if it is, I wouldn't mind that it's a lot less efficient than optimal. Any inverter with more power than that is in a whole different price range. And if I could just use the Suaoki's inverter, I wouldn't have to buy or assemble anything else, and by my count its $164 price would be considerably cheaper than building Capt. Loki's 4-part rig:

$69 -- Battery -- U-1, 33 AH
$15 -- case (would like one with a handle and room for all these items)
$50 -- charger
$68 -- ResMed converter (or $85, depends)
-----------
$202.00 TOTAL

Even if I do have to get the converter, it looks like it and the Suaoki are only about $30 more than that. But even then, I'd like to be sure it would be adequate.

[JHC]

Following up on my earlier message, I see there are a couple other 222WH inverters at the same price or $10 cheaper. With even more broken English in their descriptions on Amazon -- I don't know if that is a red flag, but it might be.

https://www.amazon.com/Generator-60000m ... 07LFWNGN6/
https://www.amazon.com/Mpow-Generators- ... 07JM7HVZF/
https://www.amazon.com/Portable-Generat ... YVG4G?th=1

They also say 60,000 mAH, which means 60 AH, right? I had read on here that Amp-hours is Watt-hours divided by 12, with a 12-volt battery. But like I wrote before, that would make these 18.5 AH, not 60 AH. What's up with that?

[palerider]

Following up on my earlier message, I see there are a couple other 222WH inverters at the same price or $10 cheaper. With even more broken English in their descriptions on Amazon -- I don't know if that is a red flag, but it might be.

https://www.amazon.com/Generator-60000m ... 07LFWNGN6/
https://www.amazon.com/Mpow-Generators- ... 07JM7HVZF/
https://www.amazon.com/Portable-Generat ... YVG4G?th=1

They also say 60,000 mAH, which means 60 AH, right? I had read on here that Amp-hours is Watt-hours divided by 12, with a 12-volt battery. But like I wrote before, that would make these 18.5 AH, not 60 AH. What's up with that?

Lithium batteries quote their ah at lithium voltages, typically 3.6v, plus they multiply by 1000 because 60,000mah looks bigger than 60ah.

So, 60ah on a lithium pack is around 216 wh. Or around 17ah@12.6v

[JHC]

AH. So if they were putting out that low voltage, to power a USB device or something thru the USB port, they would be 60 AH, but putting out 12 volts from the 12-volt connection, they'll be around 17 or 18.

[CapnLoki]

Following up on my earlier message, I see there are a couple other 222WH inverters at the same price or $10 cheaper. With even more broken English in their descriptions on Amazon -- I don't know if that is a red flag, but it might be.

https://www.amazon.com/Generator-60000m ... 07LFWNGN6/
https://www.amazon.com/Mpow-Generators- ... 07JM7HVZF/
https://www.amazon.com/Portable-Generat ... YVG4G?th=1

They also say 60,000 mAH, which means 60 AH, right? I had read on here that Amp-hours is Watt-hours divided by 12, with a 12-volt battery. But like I wrote before, that would make these 18.5 AH, not 60 AH. What's up with that?

As PR says, amp-hours have to be figured a the cell output level. When the world was all 12V there was no problem. This is why lithium is now measured in watt-hours, to avoid confusion.

The unfortunate part of all of this is that the previous ResMed is much more efficient, and the current and previous Respironics model are more efficient and run off 12 v directly. If you're thinking of a backup machine that would also be a "beater" for camping, a used Respironics 560 might fit the bill. It would only use 6AH and could run the night on a small AGM, maybe 8AH.

Missing in your comparison is that my AGM system has extra advantages. The BatteryTender charger is a "last a lifetime" item that can charge (all be it slowly) an automotive battery, and you priced the big one, not the $25 baby. The case is optional, if the terminals are taped. And the 35AH AGM can easily jump start a car - most "jump starters" have a 18AH AGM battery inside. And the battery can cheaply be replaced or upgraded. The ResMed dc-dc converter is an unfortunate quirk but it really is a necessary part of a backup/camping system.

Of course lithium has its advantages, and the price is coming down, so if you have a need of the light weight, its worth try to make it work.

[palerider]

AH. So if they were putting out that low voltage, to power a USB device or something thru the USB port, they would be 60 AH, but putting out 12 volts from the 12-volt connection, they'll be around 17 or 18.

Ah is just part of the capacity rating. You have to multiply by voltage to get the actual power capacity.

You'd have to divide the wh by 5 or so for the USB capacity, minus a little for losses in the boost converter that raises the 3.6 to 5v.

Just convert everything to wh so you're talking to .

[JHC]

Went back and looked at the SUAOKI's worst reviews -- sobering. A couple people noted that it says right on it that it's 20,000 not 60,000 -- hopefully that just means that the 20,000 is the figure for 12-volt use. Several noted flimsiness of this or that part, so that certain ports would never work.

[JHC]

The BatteryTender charger is a "last a lifetime" item that can charge (all be it slowly) an automotive battery, and you priced the big one, not the $25 baby.

I got the idea from your landmark posts that I should get the $50 one, but I forget why. The Junior should be fine for my purposes if it can charge the battery overnight (I'm alternating campsites with electricity and without).

[CapnLoki]

The BatteryTender charger is a "last a lifetime" item that can charge (all be it slowly) an automotive battery, and you priced the big one, not the $25 baby.

I got the idea from your landmark posts that I should get the $50 one, but I forget why. The Junior should be fine for my purposes if it can charge the battery overnight (I'm alternating campsites with electricity and without).

As a long term "battery tender" the baby (0.75 amps) is fine. If you want to charge larger batteries in day or two, or you want to run it continuously in "UPS" mode, the medium (1.25 amps) or even large (5 amps) may be better. I have the baby plus a larger automotive charger.

[palerider]

. A couple people noted that it says right on it that it's 20,000 not 60,000 -- hopefully that just means that the 20,000 is the figure for 12-volt use.

It doesn't work that way.

[Goofproof]

The BatteryTender charger is a "last a lifetime" item that can charge (all be it slowly) an automotive battery, and you priced the big one, not the $25 baby.

I got the idea from your landmark posts that I should get the $50 one, but I forget why. The Junior should be fine for my purposes if it can charge the battery overnight (I'm alternating campsites with electricity and without).

As a long term "battery tender" the baby (0.75 amps) is fine. If you want to charge larger batteries in day or two, or you want to run it continuously in "UPS" mode, the medium (1.25 amps) or even large (5 amps) may be better. I have the baby plus a larger automotive charger.

Yes, bigger may be better, depending on the time you have to recharge the level you use. Jim

[JHC]

"Larger batteries" means considerably larger than the 35-ish AH U-1, right?

Because I'm preparing for camping, not a backup system. One night charging it, then one night using it, etc.

[/quote]
As a long term "battery tender" the baby (0.75 amps) is fine. If you want to charge larger batteries in day or two, or you want to run it continuously in "UPS" mode, the medium (1.25 amps) or even large (5 amps) may be better. I have the baby plus a larger automotive charger.
[/quote]

[CapnLoki]

"Larger batteries" means considerably larger than the 35-ish AH U-1, right?

Because I'm preparing for camping, not a backup system. One night charging it, then one night using it, etc.

As a long term "battery tender" the baby (0.75 amps) is fine. If you want to charge larger batteries in day or two, or you want to run it continuously in "UPS" mode, the medium (1.25 amps) or even large (5 amps) may be better. I have the baby plus a larger automotive charger.

Actually, its all a big balancing act. Your Airsense will use about 7 amp-hours (no humidity, pressure 10) so the Jr will take 10 hours to mostly recover that. However, the "acceptance" of a battery drops as it approaches 100% so you'll have trouble "topping off." If you really alternate nights with and with power there won't be a problem, but if you really drained the U1 battery (several nights or using humidity) it would take more time for the Jr to recover that. Remember, the BatteryTenders are designed as trickle chargers, and in that role the Jr can handle large batteries - up to 200 amp-hours.

[JHC]

Thanks. In the meantime I found a chart which made me understand something that must be obvious to many of you, but which I hadn't had occasion to think of before: A 1-amp charger will take roughly one hour to restore one amp-hour to a battery. I hadn't really thought about what the amps number on a charger meant. I looked at several available ones with more amps, and then I looked at the $18 one I had bought at Wal-Mart that lacked ring-terminal cables, and it was 3 Amps.

So I will try to stick with that charger -- there seem to be no cables/connectors for sale that specifically went with it, so I ordered Battery Tender brand ring-terminal cables and cigarette-lighter charger, and I hope their quick-connect plugs are compatible with the charger's ones. If they aren't, they I guess I'll go ahead and buy a Battery Tender charger which I would have had to do anyway.

Resmed's Battery Guide says that the AirSense 10, delivering a pressure of 12, will need 13 amp-hours a night. (However, that figure includes "a 50% safety margin" as it will actually draw a little over one amp.) The doctor says my machine's pressure averages a little over 12.

[CapnLoki]

...
So I will try to stick with that charger -- there seem to be no cables/connectors for sale that specifically went with it, so I ordered Battery Tender brand ring-terminal cables and cigarette-lighter charger, and I hope their quick-connect plugs are compatible with the charger's ones. If they aren't, they I guess I'll go ahead and buy a Battery Tender charger which I would have had to do anyway.

Resmed's Battery Guide says that the AirSense 10, delivering a pressure of 12, will need 13 amp-hours a night. (However, that figure includes "a 50% safety margin" as it will actually draw a little over one amp.) The doctor says my machine's pressure averages a little over 12.

There's no law against you (or a friend) splicing on the appropriate connector.

As for safety margin, I prefer to work with actual load and charge rates, and then say you shouldn't take a battery below 20%. (Those running the battery every day and want the longest life would say 50%.)