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Some added info, many don't realize. Digital voltmeter measure voltage at such low amperage, just measuring the voltage has little to do with how much battery capacity is in the battery. To measure the charge in a lead acid battery requires a hydrometer. A battery needs to be put under a load to measure voltage.

Also you can buy passover humidifiers for XPAP that hook in series in the F low stream, they provide some moisture, most likely enough for camping, and use NO power! Jim

Thanks! That Napa just says maintenance on its faceplate and in a brochure that is hard to find. Better to go with a good trickle charger, so I will get a good one and reserve the old Napa for when the battery needs a more serious 10 amp charge. I appreciate the advice!

nast70 wrote:Been on my S9 for about 7 months and really enjoying the long streches of sound sleep.
For this summer i have been playing around with couple different set ups for this falls off grid week long trip. So far the best result was 4 nights with a 12v battery, 325 watt converter and a small solar panel.
The converter was old and had a very noisy fan. I tried a couple other new converters, but they have low battery alarms that would go off in the middle of the night. I think they were more for cars that are in motion that 12v deep cycle. Instead of going back to the old converter i splurged on the Resmed 12v adapter. Going to try it out this weekend and see how much it drains the battery.

I think you're on the right track. I have the Phillips Respironics but the AC is converted to 12v in the adapter. Your Resmed 12v adapter should work and be much more effcient than having to power an inverter as you know.

klv329 wrote:Thanks! That Napa just says maintenance on its faceplate and in a brochure that is hard to find. Better to go with a good trickle charger, so I will get a good one and reserve the old Napa for when the battery needs a more serious 10 amp charge. I appreciate the advice!

BTW, you really want a good "float" or maintainer charger if you're going to leave the charger connected full time. Even the "trickle" charger can mess up the battery over a period of many months.

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Deep Cycle Batteries

If you're only going to use it a few times a year, you may get by just fine even with a non-deep cycle battery. I haven't got really good numbers, but it's been suggested that even 10 - 20 fairly deep discharges won't do a lot of damage to a regular car battery.

archangle wrote:

klv329 wrote:Thanks! That Napa just says maintenance on its faceplate and in a brochure that is hard to find. Better to go with a good trickle charger, so I will get a good one and reserve the old Napa for when the battery needs a more serious 10 amp charge. I appreciate the advice!

BTW, you really want a good "float" or maintainer charger if you're going to leave the charger connected full time. Even the "trickle" charger can mess up the battery over a period of many months.

So what's the difference between a "float/maintainer" and a "trickle" charger? And which category does the BatteryTender fall in? As I've said, a problem with using the smaller BT as a full time UPS is that it has to work 24 hours a day to keep up and the battery gets cycled every day. Perhaps its better to use the 5 amp version. I setup in UPS mode (with 1.25 amp BT) several times a year, when storms are predicted.

archangle wrote: Deep Cycle Batteries

If you're only going to use it a few times a year, you may get by just fine even with a non-deep cycle battery. I haven't got really good numbers, but it's been suggested that even 10 - 20 fairly deep discharges won't do a lot of damage to a regular car battery.

Since I tend to be rather conservative on this issue, I'd say 10-20 times a year is really pushing it. Look at it this way: if you left your car lights on overnight 10-20 times a year, how long would you expect your battery to last? If it was only 2-4 times a year, you might be able to claim the battery is going to die of old age/neglect in 5 years anyway, so it really doesn't matter. Also, if you're saying you could just use the car battery that got you into the woods (and you expect to get you out in the morning) I'd say that's not a very good long term solution. On the other hand, if you have an extra older starter battery that has some life left, you might as well use it up! But if you're buying a battery for the purpose, you really should get the proper type.

Here's a discussion of the issue with a comparison chart about half way down:
http://batteryuniversity.com/learn/arti ... _batteries
I generally assume such studies are "idealized" and in real life situations performance is about half as good.

Thanks for the replies, everyone. It's nice to see the many ways XPAP users have found solutions to maintaining therapy off the grid. My study was in spring of 2000, and my life improved immediately. Fifteen years later, trying to nap or sleep without the machine seems all but impossible. Getting the right set-up, therefore, is extremely important to me and I welcome any and all observations and discussion. Here's what I've got so far...

Thanks to you all, I ordered this new 12V 70AH for use as a primary battery back-up: http://www.amazon.com/gp/product/B004WL ... FO4IXVZNRN
Question: Do I want a charger or a maintainer or both? Model numbers /links to products greatly appreciated.

ALSO, my next door neighbor gave me a 10 year-old Optima Red Top deep cycle battery. it was completely discharged, but seemed to take and hold a full charge so if it's worth keeping, I'd like to use it as a back-up back-up.
Question: Is it worth keeping, and how can I tell? Should I just hook it up to my back-up Remstar Plus and see how long it runs until it doesn't anymore?

Thanks again, all for the forum and your participation.

Best,
Bill

CapnLoki wrote:
So what's the difference between a "float/maintainer" and a "trickle" charger? And which category does the BatteryTender fall in? As I've said, a problem with using the smaller BT as a full time UPS is that it has to work 24 hours a day to keep up and the battery gets cycled every day. Perhaps its better to use the 5 amp version. I setup in UPS mode (with 1.25 amp BT) several times a year, when storms are predicted.

A trickle charger continues to charge regardless of the battery voltage. The idea is to try to match the self discharge rate with the charge rate of the trickle charger. This is difficult to do and you usually end up "cooking" the battery.

A float maintainer charges to a specific voltage, then shuts off. When the batteries voltage drops to a specific value, it turns back on and charges it back up. This keeps the battery fully charged and only charges when needed.

The Battery Tender is a float maintainer charger.

HoseCrusher wrote:
A float maintainer charges to a specific voltage, then shuts off. When the batteries voltage drops to a specific value, it turns back on and charges it back up. This keeps the battery fully charged and only charges when needed.

Can a float maintainer remain hooked up while powering the XPAP?

Yes.

HoseCrusher wrote:

CapnLoki wrote:
So what's the difference between a "float/maintainer" and a "trickle" charger? And which category does the BatteryTender fall in? As I've said, a problem with using the smaller BT as a full time UPS is that it has to work 24 hours a day to keep up and the battery gets cycled every day. Perhaps its better to use the 5 amp version. I setup in UPS mode (with 1.25 amp BT) several times a year, when storms are predicted.

A trickle charger continues to charge regardless of the battery voltage. The idea is to try to match the self discharge rate with the charge rate of the trickle charger. This is difficult to do and you usually end up "cooking" the battery.

A float maintainer charges to a specific voltage, then shuts off. When the batteries voltage drops to a specific value, it turns back on and charges it back up. This keeps the battery fully charged and only charges when needed.

The Battery Tender is a float maintainer charger.

I was curious about your terminology so I did a bit of research. Frankly, I haven't heard "trickle" being used in a formal sense in years, and my seemingly high quality chargers all claim their "float" circuitry is the best. What I found seems to be backwards from your definitions.

Here's BatteryTender's take:
http://www.batterytender.com/Float-Charging/
They are a bit vague, but seem to imply float means temperature compensated constant voltage. They admit pros and cons, but claim its the best in the long run.

Exide (they make of a LOT of batteries in the USA) provides this table:
http://www.exide.com/Media/files/Downlo ... 5_9_13.pdf
Float is defined as constant voltage: "Float charge is a stage where the battery is charged at a lower voltage to slowly "top off" a slightly discharged battery."
Trickle charging bounces between on and off points: "Trickle charging is used to maintain charge during a long storage period. Charge voltage on/off points are very important to hold charge without damaging battery life."

In practice, I think most "3 stage" and "4 stage" chargers use a float rather than trickle charge (using Exide's definition) and I'm not sure it makes a huge difference as long the the voltages don't get too far out of whack. I am thinking that my boat's solar winter storage system which is "float" on sunny days, but self-discharges a bit at night and during cloudy days, is gentler on the batteries than I thought. Six years on the current set and still going strong!

Exide is adding a "smart" trickle charger to the mix. The Battery Tender starts charging at a lower voltage, then shuts off at a target voltage. This is what Exide calls "trickle charging." If you purchase an Exide trickle charger it will charge at a constant current forever. At least that has been my experience. Exide may have advanced chargers but they usually cost more and many people go for the cheapest charger they can find.

Just looking at performance... If your charger continues to charge regardless of battery voltage, it will ruin your battery. If your charger charges to a target voltage then shuts off, it will keep your battery charged and not cook it.

HoseCrusher wrote:Exide is adding a "smart" trickle charger to the mix. The Battery Tender starts charging at a lower voltage, then shuts off at a target voltage. This is what Exide calls "trickle charging." If you purchase an Exide trickle charger it will charge at a constant current forever. At least that has been my experience. Exide may have advanced chargers but they usually cost more and many people go for the cheapest charger they can find.

Just looking at performance... If your charger continues to charge regardless of battery voltage, it will ruin your battery. If your charger charges to a target voltage then shuts off, it will keep your battery charged and not cook it.

OK. So after reading this, I looked at my slightly discharged 35 AH AGM battery, it was resting at about 12.9 Volts. (Although the "fully charged" voltage of lead acid is often claimed to be 12.6V, with no load at all it often sits a bit higher.) I put it on my BatteryTender which briefly showed "Charging" and about 10 seconds later showed "Charging but over 90% Charged" - at this point the voltage was 13.9. An hour later it showed "Charged" and the voltage was at 13.1V. The temperature was around 67, which would mean of compensation of 0.2 degrees, implying a target voltage of 12.9, which is pretty close to Exide's 12.75 "on point."

Similarly, when I visited my boat on Sunday, I noticed the solar panel regulator saying it was charging at well over 13 volts, presumably recharging the previous night's self discharge. By the time I left it was about 12.9v, implying the that regulator also "shut off" because the batteries had reached the target voltage.

Without more precise measurements, its hard to say exactly what type of charger the BT is, but I feel comfortable saying its gentle on the battery.

Keep in mind that the resting for plate style batteries is 12.6 - 12.7 volts. With AGM style it is slightly higher at 12.8 - 12.9 volts.

I agree that the Battery Tender does a good job of taking care of batteries.

My next door neighbor gave me a 10 year-old Optima Red Top deep cycle battery. it was completely discharged, but seemed to take and hold a full charge so if it's worth keeping, I'd like to use it as a back-up back-up.

Question: Is it worth keeping, and how can I tell? Should I just hook it up to my back-up Remstar Plus and see how long it runs until it doesn't anymore?

Here is a test you can do. At room temperature charge the battery fully. Let it sit for 24 hours, then measure its voltage.

If the resting open circuit voltage is 12.8 you are fully charged. If it is 12.4 you are at 50% and if it is 12.2 you are at 25%.

The next step is to apply a load to the battery and measure the voltage under load. The load ideally should be close to the load you expect to use your machine at and can be set up by using 12 volt lights wired together. If the voltage drops too low your xPAP machine will not run properly.