New Battery and Amp-Hour Data

Recently I ran into a nifty little Amp-Hour meter that will allow for reading the power used by a xPAP for a full night. It is marketed for the model RC car and plane market but is useful for measuring any small loads.
http://www.amazon.com/Watts-Meter-Analy ... 001B6N2WK/
This prompted me to sort out my battery backup system and get a new battery. I selected a U1 sized AGM battery - U1 batteries are commonly used for mobility carts and wheelchairs; they weigh about 24 pounds and provide 35 Amp-hours of charge, at a cost of about $65. It is about half the size of a small automotive battery. AGM batteries are lead-acid, but the acid is contained in a fiberglass mat and cannot spill or leak and are often used inside a house.

For a charger I use a "Battery Tender Plus" which provides 1.25 Amp. It is designed for low power trickle charging to maintain batteries when not in use. There is a smaller version, the Junior which is .75 Amp, and a larger 5 Amp version which would be better if you wanted to charge quickly. They all come with a quick connect cable to connect the battery to the charger, and you probably want to add a cigarette lighter socket for connecting to an XPAP. The connections ensure proper polarity. The total cost for the essentials is about $110, with and extra $20-40 for some nice stuff like a box, and additional cables so it can also charge cell phones and tablets, etc. I put quick connectors on the amp-hour meter so I could add it to any circuit and analyze the load. I use the charger full time to ensure the battery is not drained too much at night and can fully recharge during the day.

I've used this for the last few nights to measure the load of my Philips Respironics System One Auto 560. It is set to a pressure of 9 and only occasionally goes up to 10 - the average is 9.2. Ramp is off, and all settings are on the "middle" values. The leak rate is low. Water was topped off and room temp. The first night room humidity was 38% - a bit too dry to go without the humidifier, but I took one for science! Amp-hour numbers are normalized to 8 hour nights.

Results so far:
Night 1 - humidifier off (passive only) 4.07 Amp-Hours 38% humidity
Night 2 - humidifier on 3, plus heated hose 19.34 Amp-hours 38% humidity
Night 3 - humidifier on C3, NO heated hose 19.95 Amp-hours 47% humidity; Classic humidity
Night 4 - humidifier on 3, plus heated hose 19.04 Amp-hours 44% humidity
Night 5 - humidifier on 3, plus heated hose 19.80 Amp-hours 38% humidity
Night 6 - humidifier on 2, plus heated hose 17.12 Amp-hours 42% humidity
Night 7 - humidifier on 3, NO heated hose 11.35 Amp-hours 42% humidity
Night 8 - humidifier on 3, NO heated hose 12.49 Amp-hours 41% humidity
Night 9 - humidifier on C3, NO heated hose 22.88 Amp-hours 42% humidity; Classic humidity
Night 10 - humidifier on 2, NO heated hose 8.96 Amp-hours 39% humidity
Night 11 - humidifier on 2, NO heated hose 7.38 Amp-hours 36% humidity
Night 12 - humidifier on 3, NO heated hose 20.1 Amp-hours 38% humidity *Using Inverter*

A few observations:
As you can see, I bounced around some with the settings as I understood more and wanted to try new things and verify results. There is considerable variation and would probably take a month or so of reading to really get a full picture, but we can start to make rough estimates: The load of the Pump itself seems to be 4 Ah. S1 humidity seems to add about 8 Ah at "3," maybe 6 Ah at "2." The Heated Hose appears to add about 7 Ah. Classic humidity at "C3" without a hose adds about 16-18 Ah, clearly the highest.

A full tank of water is 325 ml or 0.71 pounds, so bringing it from room temperature (say 67 degrees) to the heating plate temp (167 degrees) uses 71 BTU or about 21 Watt-hours or 1.75 Amp-hours. If you can preheat the water, and only fill the amount to be used, you can save a lot of power.

As the water evaporates, it takes heat from the tank; for the entire tank this comes to about 18 Amp-hours. In Classic Mode, I think the plate maintains a constant temperature, but the power used will vary according to how much water actually evaporates. which will depend on many factors. In S1 mode, it tries to maintain a a constant humidity, but again, it depends on many factors. And of course the heated hose doesn't add humidity, it simply prevents "transmission loses" in the hose, but at a considerable cost.

The water usage was roughly half a tank per night - in line with the power draw. I would expect much lower water usage (and thus current draw) in the summer with higher ambient humidity. I could not closely correlate water usage with current draw.

Unfortunately I can't quantify to comfort level - I tend to vary between "no so bad" and "why am I so parched?" randomly and its hard to remember in the morning how bad it was. Clearly the "no active humidity" was the worst, but I've lived with that many times while travelling or on my boat so I guess it doesn't bother me that much, as long as the ambient humidity is not too low. With power to spare, especially in the dry season, I'll use the humidifier, but its nice to know I can get by without it.

There are a few more things I want to try - for instance level "1", no hose, for the minimal active humidity. I'll add updates as I collect data.

This is sooooo useful. Thanks for this!!!!!!!!!! Can you provide a link to the battery you use? It's OK if you can't because the info is TOPS!

Pesser wrote:... Can you provide a link to the battery you use?

This is the battery:
http://www.amazon.com/Wheelchair-Scoote ... B00N414YMC
Although it says "pair" its only one battery - I think the scooter its often used in takes two. There are other U1 batteries on Amazon for aboutt $65 - I picked this because of the $10 promo code. This is fine for home use where the weight is not a problem, but for travel the new LiFePo4 options are interesting, half the weight though three times the price!

Thanks for this CapnLoki! Now I have a much better picture of how long my back up battery system will last.

I've added three more nights to list - I've edited the original

Night 10 - humidifier on 2, NO heated hose 8.96 Amp-hours 39% humidity
Night 11 - humidifier on 2, NO heated hose 7.38 Amp-hours 36% humidity
Night 12 - humidifier on 3, NO heated hose 20.1 Amp-hours 38% humidity *Using Inverter*

Nights 10 and 11 were an attempt to find a setting the provides some humidity without costing too much juice. Eliminating the heated hose was a big step, dropping S1 humidity to "2" lowers the draw to roughly half of my normal setting (hose 3, S1 3). At this level my battery can run for three nights with a 20% margin. I don't think I've ever directly experienced a longer outage.

Night 12 was really a test of inverter efficiency under "real world" conditions. Comparing to the two similar runs using direct DC, this implies lower than 60% efficiency - in line with the ResMed battery doc and my tests from last year. The inverter is a cheap Bestek 150 Watt from Amazon.

I have been lurking for a while but had to make an account to thank you for this information. I am now ready to make my camping rig.

abandoned_doge wrote: I have been lurking for a while but had to make an account to thank you for this information. I am now ready to make my camping rig.

Thanks, I appreciate that. I do have to say that while I stand by my recommendation of the MotoBatt battery, the price for it was very high the last time I looked. You should be able to find a U1 battery for about $65.

CapnLoki wrote:

abandoned_doge wrote: I have been lurking for a while but had to make an account to thank you for this information. I am now ready to make my camping rig.

Thanks, I appreciate that. I do have to say that while I stand by my recommendation of the MotoBatt battery, the price for it was very high the last time I looked. You should be able to find a U1 battery for about $65.

I'm SO GRATEFUL as well! I live in Altamonte Springs, FL, the "lightning capitol of the world," and if the power goes off, NO SLEEP FOR ME! That changes now, thanks to this thread.

CapnLoki: two questions...
1. How many nights consecutive use do you think you would get -- without the maintainer -- on a full charge using your setup and usage?
2. Would this battery be the right one for me to get, given that my goal is to get maximum nights between charges? http://www.amazon.com/gp/product/B001VV ... V2YRRJEBAG

Thanks again, so very much, for sharing your knowledge and experience.

-Bill

-Bill

CapnLoki wrote:

Pesser wrote:... Can you provide a link to the battery you use?

This is the battery:
http://www.amazon.com/Wheelchair-Scoote ... B00N414YMC
Although it says "pair" its only one battery - I think the scooter its often used in takes two. There are other U1 batteries on Amazon for aboutt $65 - I picked this because of the $10 promo code. This is fine for home use where the weight is not a problem, but for travel the new LiFePo4 options are interesting, half the weight though three times the price!

This battery now on Amazon for $97. Is this the one you have? http://www.amazon.com/Wheelchair-Scoote ... B00N414YMC

CapnLoki. As they used to say in the 70's... you da man!

NomoreCrashcart wrote:

CapnLoki wrote:

Pesser wrote:... Can you provide a link to the battery you use?

This is the battery:
http://www.amazon.com/Wheelchair-Scoote ... B00N414YMC
Although it says "pair" its only one battery - I think the scooter its often used in takes two. There are other U1 batteries on Amazon for aboutt $65 - I picked this because of the $10 promo code. This is fine for home use where the weight is not a problem, but for travel the new LiFePo4 options are interesting, half the weight though three times the price!

This battery now on Amazon for $97. Is this the one you have? http://www.amazon.com/Wheelchair-Scoote ... B00N414YMC

Yes, but at $97 its way overpriced! (I paid about $60.) I would go for the UB12350 which should be about $65. Also, there's nothing magical about this particular size (U1), it just seemed a good size that puts out a fair amount of power and is still luggable. SInce its commonly used in scooters you should be able to find one at a good price.

BTW, my battery is currently in the living room powering the boat electronics I bought on Black Friday! It won't get installed until April, so I thought I'd fire it up for a smoke test.

NomoreCrashcart wrote:

CapnLoki wrote:

abandoned_doge wrote: I have been lurking for a while but had to make an account to thank you for this information. I am now ready to make my camping rig.

Thanks, I appreciate that. I do have to say that while I stand by my recommendation of the MotoBatt battery, the price for it was very high the last time I looked. You should be able to find a U1 battery for about $65.

I'm SO GRATEFUL as well! I live in Altamonte Springs, FL, the "lightning capitol of the world," and if the power goes off, NO SLEEP FOR ME! That changes now, thanks to this thread.

CapnLoki: two questions...
1. How many nights consecutive use do you think you would get -- without the maintainer -- on a full charge using your setup and usage?
2. Would this battery be the right one for me to get, given that my goal is to get maximum nights between charges? http://www.amazon.com/gp/product/B001VV ... V2YRRJEBAG

Thanks again, so very much, for sharing your knowledge and experience.

-Bill

-Bill

Just noticed your first post -
With my pump and pressure, I think I figured 5-7 nights without any humidity, but only 2-3 with minimal humidity, and only one full night with my normal "full comfort" setup. However, if you're really concerned with long power outages, the easy solution is simply get a large battery. Some people make do with traditional flooded deep cycle batteries that have triple the capacity of this U1 size for only a few dollars more. However, I wouldn't like having one of those in the bedroom (although I have 4 on my boat) so I'd rather pay the bucks for a larger AGM.

Only you can decide the best battery to get. And there's nothing wrong with have two batteries, etc. On the boat I'm "belt and braces" so I have 6 batteries, two engine driven alternators, one genset, and 5 solar panels. But at home I have fairly reliable power so I'm comfortable with the one small battery, which I can charge with the car if need be.

Wow, this info is exactly what I was looking for, especially since you use the exact same machine and settings as I do! Thank you thank you thank you! I do have one question: how do you charge the battery with your car?

Kate
St. Louis, MO

mafouka wrote:Wow, this info is exactly what I was looking for, especially since you use the exact same machine and settings as I do! Thank you thank you thank you! I do have one question: how do you charge the battery with your car?

Kate
St. Louis, MO

I'm glad you found this useful. I have another post that describes the battery setup in more detail - last post in this thread:
viewtopic.php?t=102775

The simple answer to "how do you charge with a car?" is just plug it into the cigarette lighter or use jumper cables. For a better answer you'd have to describe the battery and cables you have. One thing to remember is that the amount of charge that a battery will accept is proportional to its size. And since you don't want to go much below 50% and the last 15% can be tedious to top off, "off grid" users such as boaters and RVers will often discharge to 50% and charge up to 85% on a daily basis. Most batteries will do this in an hour or so if the charge source (i.e. your car's alternator) can provide enough juice. So for a U1 mobility cart battery this might give you 12 Amp-hours, but for a larger "car size" battery that might be 20 to 30 Amp-hours. Another way to look at this is that a large battery will accept a fair charge in a 30 minute drive, but a smaller battery might take an hour to recover the same amount.

One more thing to remember: most car alternators don't "turn on" at idle. To get the voltage up to good fast charge level you have to rev the engine a bit (not a lot!). My boat alternator turns on at about 1400 RPM and I run at between 1800 and 2000 when I'm charging.

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