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I have a 120 Amp/hr Deep Cycle wet cell battery that I use as a uninteruptable power supply, that I use a battery-tender plus to charge the battery continuously. Depending on the humidifier setting the charger will switch from float mode to charge mode about every 3 to 4 days. it has been running like this for over 2 years with no trouble. But I did modify the Battery-Tender Plus slightly, I sanded the paint off the back of the charger and attached a 2.5 X 4 X 2 in heat sink to it, over where the output transistors are located to help keep it cool. I did this because I didn't want to open it up and void the warranty. I haven't measured it yet, but I think the charger is now able to put out more than the 1.25 Amps that it is rated for. I went camping last year and I was able to get 4 nine hour sleep sessions with the humidifier without recharging, I think I could have gone a few more days but didn't want to push it.

mstevens wrote:In other news, now that I've switched from a Battery Tender Junior to a Battery Tender Plus (1.25 amps, about double the charging rate of the Junior) my battery is now somewhere above 80% charged. That's from Sunday morning until Tuesday night on the Junior and overnight on the Plus.

It finally dawned on me, duh. If you suck 50 amp-hrs out of the battery during the night, and your charger puts it back in at 1.25 amps charge rate, it'll take 40 hours at 100% efficiency to get it all back in. I don't know what the recharge rate capacity of a deep cycle battery, but I'm sure it ain't 50 amps like a car battery. Otherwise mine would have charged up a lot faster than it did from the pickup. I have a disconnect on the pickup battery so when I was charging the deep cycle all the power from the alternator was going into it. Supposedly the pickup alternator is capable of putting out 70 amps. I'm sure the deep cycle wasn't taking it in any faster than about 10 amps.

I just checked my float charger. It's rated at 1.5 amps so it could not have charged up my battery near as fast as I was thinking. It was probably over two days.

I just did some surfing on chargers that would allow you to use the battery in UPS style. They are available, but looks like they're in the $75 to $125 range, for 6 to 10 amp capacity.

Many battery chargers with more than an amp or two of charging current will eat your deep cycle battery. They're just not designed right to be connected full time. Even some battery chargers that claim to go into trickle mode will eat your battery within a year or two. Even some of the little "trickle only" chargers will kill your battery if connected full time.

I know, I've killed 2 or 3 marine batteries this way with the wrong charger.

In concept, you should be able to find a higher current charger that won't eat your battery. Unfortunately, until you've tried it a year or two, you don't know. I do know that just because it's a "high end" model from a "respected" manufacturer, that doesn't mean it won't eat your battery. I've seen some of them that slowly cook the battery and some that occasionally don't throttle back and will cook the battery.

It's a lot simpler if you only use the battery when there's a power failure.

I'm also a little concerned about the safety of using a non-medical approved charger hooked into your CPAP machine while you are using the machine. You could easily get 120 VAC voltage on the "ground" lead of the DC supply. It would seem that you're well normally well insulated from the CPAP machine, but what about a heated hose with wet tubing and a mask? How about if water gets in and on the machine and you touch it?

I think your problem is not using the charger when you are using the battery. My Sears uses a 1A Wall wart to keep it charged up, FULLY, with daily use.

I have said this before and I'll say it again. I think it is a mistake to expect your battery to be at a full charge if you don't keep it plugged into the charger.

btw - When you buy a 'new' battery, you don't know how long it has been sitting on the shelf. Give it 2 or 3 days, a week if you can, to charge up to FULL capacity BEFORE you start using it.

There are a couple rocket scientist on here who insist that I will kill my battery by using a continuous charge but then they post how they have killed all their batteries. So follow them, then.

Meanwhile, my jump starter is going just fine - with daily use no less.
viewtopic.php?f=1&t=64943&p=652637&hili ... ry#p652637

Cheers

archangle wrote:Even some of the little "trickle only" chargers will kill your battery if connected full time.

Trickle and float are different. That's not to say that a float charger couldn't also kill a battery, but it's very likely with a trickle charger.

archangle wrote:It's a lot simpler if you only use the battery when there's a power failure.

Yep.

archangle wrote:I'm also a little concerned about the safety of using a non-medical approved charger hooked into your CPAP machine while you are using the machine. You could easily get 120 VAC voltage on the "ground" lead of the DC supply. It would seem that you're well normally well insulated from the CPAP machine, but what about a heated hose with wet tubing and a mask? How about if water gets in and on the machine and you touch it?

Nope. There is no such thing as a "medical approved charger" in the first place, and ResMed says it's OK to plug the converter into 12-volt sockets including in running vehicles, boats, planes, etc. The worst that could possibily happen is that I might fry the DC to DC power converter. The scenario you describe is vastly more likely using the usual AC power supply, and it's not at all likely then.

GumbyCT wrote:I think your problem is not using the charger when you are using the battery.

No. That is most definitely not my problem.

As I clearly said, my battery has been continuously connected to a charger for the entire time I've owned it, except for a few seconds last night when I swapped chargers.

GumbyCT wrote:When you buy a 'new' battery, you don't know how long it has been sitting on the shelf. Give it 2 or 3 days, a week if you can, to charge up to FULL capacity BEFORE you start using it.

My battery arrived very nearly fully-charged and was fully-charged by the time I first used it.

mstevens wrote:

GumbyCT wrote:I think your problem is not using the charger when you are using the battery.

No. That is most definitely not my problem.

As I clearly said, my battery has been continuously connected to a charger for the entire time I've owned it, except for a few seconds last night when I swapped chargers.

GumbyCT wrote:When you buy a 'new' battery, you don't know how long it has been sitting on the shelf. Give it 2 or 3 days, a week if you can, to charge up to FULL capacity BEFORE you start using it.

My battery arrived very nearly fully-charged and was fully-charged by the time I first used it.

It should be working then? So just excuse the hey out of me.

mstevens wrote:

idamtnboy wrote:You may need to get two chargers, one heavy duty to do the bulk of the recharging and then a good float charger to top it off and keep it there.

It's starting to look as if that might be true. Of course, that would mean we can't make an effective uninterruptible power supply for CPAP this way - if one must switch chargers anyway, then one might as well just leave the battery on a float charger until the power goes out and use wall current the rest of the time.

To sound just like a man I will just say - "I got mine, you get yours".

Cheers

GumbyCT wrote:It should be working then?

I don't really think that a Battery Tender Junior has a charge rate (0.65 amps) that will ever keep up with the nightly rate of discharge when using it with a battery to try to make a CPAP UPS.

The good news is that, with a trial of a single night, a Battery Tender Plus does appear to suffice. My battery had fully charged by last night so I hooked everything back up so the S9 was running off the battery while the battery was connected to the BT+. This morning, the charger still indicated full charge! That probably just means that it was supplying the converter enough current so the battery had to kick in little to nothing. However, it also means that if power poops out in the middle of the night I should be able to sleep right through it and not run out of juice before I'd normally wake up.

It'll still probably take quite a while to recharge a depleted battery, though.

mstevens wrote:

archangle wrote:Even some of the little "trickle only" chargers will kill your battery if connected full time.

Trickle and float are different. That's not to say that a float charger couldn't also kill a battery, but it's very likely with a trickle charger.

You are correct on the distinction between float and trickle, although the marketing guys often stretch the truth. I've lost several deep cycle batteries to what were advertised as "float chargers" suitable for permanent connection.

mstevens wrote:

archangle wrote:I'm also a little concerned about the safety of using a non-medical approved charger hooked into your CPAP machine while you are using the machine. You could easily get 120 VAC voltage on the "ground" lead of the DC supply. It would seem that you're well normally well insulated from the CPAP machine, but what about a heated hose with wet tubing and a mask? How about if water gets in and on the machine and you touch it?

Nope. There is no such thing as a "medical approved charger" in the first place, and ResMed says it's OK to plug the converter into 12-volt sockets including in running vehicles, boats, planes, etc. The worst that could possibily happen is that I might fry the DC to DC power converter. The scenario you describe is vastly more likely using the usual AC power supply, and it's not at all likely then.

The manufacturer's AC power supply is presumably a medically approved power supply. It's double insulated, and almost certainly hipot tested. A battery charger is not designed to be hooked up to a medical device. In other words, it's a "non-medical approved charger" and there is some risk using it to power a medical device. When you hook an AC powered battery charger to the battery and hook the battery to your CPAP, you have connected your CPAP to the AC system without a medically approved electrical safety device isolating you from AC.

While the topic of this thread is "S9 battery power," some non S9 users may be reading this thread and aren't using a ResMed converter.

Even if you're using the ResMed converter, you're assuming the ResMed converter provides adequate electrical safety when connected to a battery plus AC charger. This may be true, but I'm not sure. The ResMed Battery Guide says not to start the engine while the converter is connected. It's not clear to me that it's OK to start the engine, then plug the machine in, or if it's OK to connect it once you start the engine. This may be documented elsewhere.

The manual does say the converter provides electrical isolation to the CPAP device. It's not clear that this is electrical safety isolation adequate for connection to 120 VAC power, or just for 12/24 VDC battery power. 120VAC devices present a much higher electrocution risk than the DC power systems in most vehicles.

You are theoretically still pretty well insulated unless you have a heated hose because there is 6 feet or so of plastic hose between you an the machine. The hose will be wet, so it might conduct a little electricity in theory, but I don't know if it will be enough to hurt. Clean water doesn't conduct electricity very well.

archangle wrote:You are correct on the distinction between float and trickle, although the marketing guys often stretch the truth. I've lost several deep cycle batteries to what were advertised as "float chargers" suitable for permanent connection.

Welllllll, if you wouldn't buy from Harbor Freight!!

Nope. There is no such thing as a "medical approved charger" in the first place, and ResMed says it's OK to plug the converter into 12-volt sockets including in running vehicles, boats, planes, etc. The worst that could possibily happen is that I might fry the DC to DC power converter. The scenario you describe is vastly more likely using the usual AC power supply, and it's not at all likely then.

The manufacturer's AC power supply is presumably a medically approved power supply. It's double insulated, and almost certainly hipot tested. A battery charger is not designed to be hooked up to a medical device. In other words, it's a "non-medical approved charger" and there is some risk using it to power a medical device. When you hook an AC powered battery charger to the battery and hook the battery to your CPAP, you have connected your CPAP to the AC system without a medically approved electrical safety device isolating you from AC.

While the topic of this thread is "S9 battery power," some non S9 users may be reading this thread and aren't using a ResMed converter.

Even if you're using the ResMed converter, you're assuming the ResMed converter provides adequate electrical safety when connected to a battery plus AC charger. This may be true, but I'm not sure. The ResMed Battery Guide says not to start the engine while the converter is connected. It's not clear to me that it's OK to start the engine, then plug the machine in, or if it's OK to connect it once you start the engine. This may be documented elsewhere.

The manual does say the converter provides electrical isolation to the CPAP device. It's not clear that this is electrical safety isolation adequate for connection to 120 VAC power, or just for 12/24 VDC battery power. 120VAC devices present a much higher electrocution risk than the DC power systems in most vehicles.

You are theoretically still pretty well insulated unless you have a heated hose because there is 6 feet or so of plastic hose between you an the machine. The hose will be wet, so it might conduct a little electricity in theory, but I don't know if it will be enough to hurt. Clean water doesn't conduct electricity very well.

Come on man, get real. How likely is the chance of AC current jumping through the circuitry of a charger to one of the output leads? I suppose theoretically it can happen, but you're more likely to get killed in car wreck on the way to weekend breakfast at McDonalds. And if it does happen you've got the circuitry in the converter to stop the flow. It'll probably burn up the interior of the converter. And then you've got all the circuitry of the PAP machine, which would burn up stopping a 120v current. And of course this all presupposes a return path to ground through all of the paraphernalia above, a very unlikely event. Then, if after getting through all that there is somehow 120v imposed on the hose there still almost certainly will be no path to ground. Bed clothes are insulators, and unless you have your hand or feet touching some sort of metal that connects to ground you won't conduct any electricity at all. And whatever kind of floor the bed is on, the floor most likely won't provide a good enough ground to cause a shock. And even if you do conduct 120v it will only be for a very brief moment because all the circuit components that are being breached will burn up, creating an open path. A human can tolerate a 120v shock for a few seconds. I know. Twice as a teenager I was part of a very clear 120v path to ground, once from one finger to my bare feet on dirt, and another from left hand to my right hand, right across my heart.

Oh, a final thought. Don't go walking past any modern windmills. One of the blades might fall off and slice you in two!

archangle wrote:When you hook an AC powered battery charger to the battery and hook the battery to your CPAP, you have connected your CPAP to the AC system without a medically approved electrical safety device isolating you from AC.

This is not true in my case. I'm using the ResMed DC to DC converter, which is a manufacturer-approved and US FDA-approved (there's really no such thing as "medically-approved") power supply that provides adequate isolation. The charger cannot be connected directly to the CPAP flow generator unless one opens up the box and somehow connects the charger to internal wiring. The DC to DC converter uses the same isolation circuitry as the AC charger. Thus, in the extremely unlikely event that the charger somehow ends up delivering wall current to the converter, the converter is still capable of providing adequate isolation.

I suppose what you're saying might be true in the case of an inverter or some 3rd-party converter that hasn't been engineered for medical use.

Speaking as a physician, and after having this statement reviewed by my brother who is a senior biomedical engineer in the US FDA devices division, this is not a problem I'm at all worried about.

mstevens wrote:
This is not true in my case. I'm using the ResMed DC to DC converter, which is a manufacturer-approved and US FDA-approved (there's really no such thing as "medically-approved") power supply that provides adequate isolation. The charger cannot be connected directly to the CPAP flow generator unless one opens up the box and somehow connects the charger to internal wiring.

If you'll read again, I did make the point that with the ResMed converter, you do have an extra degree of isolation.

mstevens wrote:The DC to DC converter uses the same isolation circuitry as the AC charger.

Wow, that's good to know. Where did you get a copy of the schematic from? I'd be interested in seeing that. Or is this statement documented somewhere? From the ResMed information I've seen, it appears to be intended for use connecting the CPAP to a battery, not hooking the CPAP into the 120VAC house wiring.

idamtnboy wrote:Welllllll, if you wouldn't buy from Harbor Freight!!

I learned something a long time ago from other people's bad experience. Nothing from Harbor Freight stays powered on when unattended in my house, so there are no battery charger circuits from Harbor Freight anywhere near me.

idamtnboy wrote:Come on man, get real. How likely is the chance of AC current jumping through the circuitry of a charger to one of the output leads? And if it does happen you've got the circuitry in the converter to stop the flow. It'll probably burn up the interior of the converter. And then you've got all the circuitry of the PAP machine, which would burn up stopping a 120v current. And of course this all presupposes a return path to ground through all of the paraphernalia above, a very unlikely event. Then, if after getting through all that there is somehow 120v imposed on the hose there still almost certainly will be no path to ground. Bed clothes are insulators, and unless you have your hand or feet touching some sort of metal that connects to ground you won't conduct any electricity at all. And whatever kind of floor the bed is on, the floor most likely won't provide a good enough ground to cause a shock. And even if you do conduct 120v it will only be for a very brief moment because all the circuit components that are being breached will burn up, creating an open path. A human can tolerate a 120v shock for a few seconds. I know. Twice as a teenager I was part of a very clear 120v path to ground, once from one finger to my bare feet on dirt, and another from left hand to my right hand, right across my heart.

You suffer from some very common misconceptions about electrical safety. Lots of people have died from those misconceptions, even from non-medical equipment. I'll try to address a few of them.

Lots of people have died in the from being electrocuted by medical devices. I remember back in the 1970's (?) when there was a big push to improve medical device safety and much more stringent electrical safety requirements were instituted. Quite a few electrical devices come in special "hospital" or medical grade versions. Quite a few devices are labeled as not for medical use.

Shorting the 120VAC to the low voltage secondary is not at all unlikely. There's usually a transformer somewhere in the device with 120VAC wound on a coil, a plastic insulator over the inner coil, and the low voltage "safe" side of the power supply wound over the plastic insulator. If the insulation between the 120VAC and the "safe" side melts or gets damaged, the 120 VAC can be connected to the low voltage side.

Reputable manufacturers go to quite a bit of effort to be sure this is unlikely to happen. Unfortunately there's a lot of cheap junk from China (or the USA) being sold these days that's not really up to electrical safety standards.

Tear apart one of the little wall wart DC plugs that everything seems to use these days. Look at where the AC and DC voltages go. Or look at the DC supply in a device that plugs directly into the wall. Imagine what happens if it gets hot and things start to melt. Then be afraid.

Even if the 120VAC gets through the transformer to the electrically isolated low voltage side of the electrical device, it will not necessarily burn anything out. Since it's electrically isolated, the "ground" side of the DC power supply can be at 120VAC and no extra current will flow because there's no path to ground. The device will run just fine until something provides a path to ground. Some medical devices are extra dangerous because your body is likely to be the path to ground.

You're assuming that if 120VAC gets "loose," it will "burn up" something and there will no longer be any current flowing. Even if the 120VAC damages the electrical circuitry in your CPAP, it won't necessarily vaporize it causing an open circuit. "Burned up" non-functional circuitry is often still electrically conductive.

A current that will easily kill a human being may not damage wiring and circuit boards at all. If you become the path to ground for 120 VAC, currents of around .1 amp can easily kill you. Many CPAP machines are fused at around 7 amps, so the lethal current that's killing you won't necessarily burn anything up. It's possible all the current is flowing through the "ground" side of the DC power system and doesn't pass through any electronic devices at all.

Fuses mostly protect from fire, not from electrocution. If you open up most electrical devices and touch something that's got 120VAC on it, it's very easy to get a lethal level of current and not affect the electrical device at all.

As far as humans tolerating 120VAC shocks, that's highly variable. If your skin is dry, you don't have a good ground, etc., you may touch 120VAC and not have any harm. With a good contact, you can get a very quick severe injury. I've already explained why you can't count of the device to rapidly vaporize, act as a fuse and shut off the current.

You are right that bedclothes, beds, etc. are electrical insulators. However, there are quite a few cases where you might get grounded. For instance, turning on or touching the lamp on your headboard, grabbing the telephone, touching another grounded device on the bedside table, standing barefoot by the bed masking up, etc. If you have a 120 VAC "leak" in your equipment, it may well continue to operate for years until that one day you happen to be the path to ground.

Yes, you'll probably be safe. Is "probably" good enough for you or your loved ones?

archangle wrote:As far as humans tolerating 120VAC shocks, that's highly variable. If your skin is dry, you don't have a good ground, etc., you may touch 120VAC and not have any harm. With a good contact, you can get a very quick severe injury. I've already explained why you can't count of the device to rapidly vaporize, act as a fuse and shut off the current.

Me - I'll wait for the movie.

And pray a cure is found cuz the medicine is NOT helping.

archangle wrote:You are right that bedclothes, beds, etc. are electrical insulators. However, there are quite a few cases where you might get grounded. For instance, turning on or touching the lamp on your headboard, grabbing the telephone, touching another grounded device on the bedside table, standing barefoot by the bed masking up, etc. If you have a 120 VAC "leak" in your equipment, it may well continue to operate for years until that one day you happen to be the path to ground.

IF you believe anything aa says you will be afraid to leave the house and more afraid to touch anything in it.

archangle wrote:Yes, you'll probably be safe. Is "probably" good enough for you or your loved ones?

But hey, every village had one and now NO Forum is safe.

ME thinks worry causes sleep disorders.