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WARNING to CPAP Users: PREPARE for the Unexpected - When the power goes out
RE: WARNING to CPAP Users: PREPARE for the Unexpected - When the power goes out
(06-04-2015, 01:20 AM)GWild Wrote: But having to maintain a wet battery (keep the electrolyte channels full), and that they generally don't have gas recovery caps, means a lot of work.

With my cheap 100 Ah deep cycle wet cell marine batteries, and my Schumacher SE-1-12S charger, I check the water level about every 6 months and probably only need to add water about every 2 years, if that often.

Stop and think how often you have to add water to your car battery.

(06-04-2015, 01:20 AM)GWild Wrote: A few bucks more buys an AGM.

Your definition of a few more bucks differs considerably from mine.

(06-04-2015, 01:20 AM)GWild Wrote: so a non-sealed LA car battery inside a home on a charger is a bad thing).

If you're worried about hydrogen accumulating in your room, it's unlikely to be a problem. Don't put the battery in an airtight box.

You won't get much hydrogen gas unless you have a bank of batteries or a really high current charger. The theoretical maximum amount of hydrogen a 10 amp charger can produce is about 2 ounces per day. Unless it's in a tightly sealed box, the hydrogen will dissipate rapidly and won't accumulate to high levels in a room in your house.

In practice, it would probably produce much less hydrogen. Much of the hydrogen recombines with oxygen inside the battery, even in an unsealed wet cell.

Also, in order to produce 2 ounces of hydrogen, you have to consume 18 ounces (over 2 cups) of water. Unless you're consuming water at a prodigious rate, you're not likely to have much hydrogen escaping the battery per day.

AGM/cell/VRLA/sealed lead acid batteries do have extra provisions to recombine hydrogen and oxygen, but in some cases, they produce hydrogen and will release it through a vent when the pressure builds up.

(06-04-2015, 01:20 AM)GWild Wrote: The method of constant desulfation - the theory anyway - is to use a pulsed DC circuit for controlling charge current during float. Well, most chargers were once analog brute force with little or no control of voltage or current. Then came 'smart chargers' with switching supplies. High current filter capacitors and inductors are expensive, and since a battery has a pretty solid ultra low ESR, these parts are almost pointless unless the exact battery load is known. So why not market the ripple current as a feature?

I recall some tests where it helped, some where it didn't. All depends on the battery construction. In the end, controlling the charge voltage versus temperature has a major impact on battery life, and that's where you want to spend money to get the most out of a set of batteries. That's why you see three stage chargers.

Desulfation is sort of black magic and rumor to me. My impression is that desulfating is very iffy. The trick is to prevent sulfation from happening, mostly by keeping the battery charged. You might try desulfation on a battery that's gone bad from sitting uncharged, but don't count on it to work.
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RE: WARNING to CPAP Users: PREPARE for the Unexpected - When the power goes out

Not wanting to pick nits - and we are in general agreement - but hydrogen and oxygen produced together by battery charging has resulted in explosions that have seriously injured people who were nearby. Some of these in open garages. While the specifics of just how many amps were involved is unknown, I'd rather err on the side of caution. But you can do whatever you want as long as it doesn't impact me (or my insurance rates - which - if you do explode, will impact my rates Grin).

As for how much hydrogen makes a big bang, it takes far less than 2 ounces to destroy a battery; which turns into shrapnel and damages things around it. An H2+O explosion is actually more energetic than TNT, nearly the same as dynamite. So it really doesn't take much to make your day. Again - each to their own. Some people toss fireworks after lighting them... I don't Unsure.

Sulfation is real and dealing with it is a part of maintenance. Desulfation and equalization is required any time you string cells together. Keeping each cell charged an equal amount, with equal ESR, allows a cycle to happen without undercharging or overcharging individual cells. If you read about the latest tech - the LiFePO4 batteries have charge equalization built in (if I read the lit right, this means active electronics inside the batteries). If a person maintained a well designed wet cell as stringently, they'd last 8,000 cycle, too.

On another note - I just received the DC adapter for my 560P -- I'll try to get around to setting up the meters and finding out just how much more or less power it uses than my 550P (for my 8-20cm no-flex settings, anyway). Respironics sells an SLA 14.4AH kit and spec it to last two to three days at 12cm; and their lightweight 8AH Lithium kit about half that... those times come in close to 0.65 amps nominal. The earlier measurement of my 550P at 0.8 amps is in line with that.

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RE: WARNING to CPAP Users: PREPARE for the Unexpected - When the power goes out
I'm wondering when ResMed is going to post the specs on how much power the Aircurve 10 draws on a battery, without climateline or humidifier on. It would be nice to know how long my battery would work.
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